CONSTRUCTION TECHNOLOGY

Department of Civil Enginnering

(B.Tech 4th semester)

Faculty Name : Shrabanee Giri

 CONTENTS

Properties of masonry materials – review of specifications;

Mortar – Types – Sand – properties – uses.
Timber products: properties and uses of plywood, fibre board,
particle board.
Iron and Steel –Reinforcing steel – types – specifications.
Structural steel – specifications
Miscellaneous materials (only properties, classifications and their
use in construction industry): Glass, Plastics, A.C. Sheets, Bitumen,
Adhesives, Aluminium
Concrete – Aggregates – Mechanical & Physical properties and tests
– Grading requirements –
Water quality for concrete –
Admixtures – types and uses – plasticizers – accelerators – retarders
–water reducing agents
Making of concrete - batching – mixing – types of mixers –
transportation – placing – compacting – curing
Properties of concrete – fresh concrete – workability – segregation
and bleeding - factors affecting
workability & strength – tests on workability – tests for strength of
concrete in compression, tension
& flexure
Concrete quality control – statistical analysis of results – standard
deviation –acceptance criteria – mix proportioning (B.I.S method) –
nominal mixes.

Building construction - Preliminary considerations for shallow and

deep foundations
Masonry – Types of stone masonry – composite walls - cavity walls
and partition walls -Construction details and features – scaffoldings
Introduction to Cost-effective construction - principles of filler
slab and rat-trap bond masonry

Tall Buildings – Framed building – steel and concrete frame –

structural systems –erection of steel work–concrete framed
construction– formwork – construction and expansion. joints
Introduction to prefabricated construction – slip form construction
Vertical transportation:
Stairs – types - layout and planning-
Elevators – types – terminology – passenger, service and goods
elevators – handling capacity - arrangement and positioning of lifts –
Escalators – features –use of ramps

Building failures – General reasons – classification – Causes of

failures in RCC and Steel structures, Failure due to Fire, Wind and
Earthquakes.
Foundation failure – failures by alteration, improper maintenance,
overloading.
Retrofitting of structural components - beams, columns and slabs
Dept. of Civil Engineering
MODULE 1
MODULE 1
Syllabus:
Properties of masonry materials – review of specifications;
Mortar – Types – Sand – properties – uses.
Timber products: properties and uses of plywood, fibre board, particle board.
Iron and Steel –Reinforcing steel – types – specifications. Structural steel – specifications
Miscellaneous materials (only properties, classifications and their use in construction industry): Glass,
Plastics, A.C. Sheets, Bitumen, Adhesives, Aluminium.

MORTAR
DEFINITION

Mortar is the term used to indicate a paste prepared by adding required quantity of water to
mixture of binding material (like cement) and fine aggregate (like sand)
Water
Binding Material + Fine Aggregate Mortar
Here Fine aggregate act as the Adulterant which provides the volume to the mortar and Binding
material acts as the Matrix which binds the particles of adulterant. Durability, quality and strength of
the mortar depends on the matrix.

SAND
Sand is an important ingredient of mortar

Natural sources of Sand

The sand particles consist of small grains of silica (SiO2). It is formed by the decomposition of
sandstones due to various effects of weathering. According to the natural sources from which the sand
is obtained, it is of following three types
1. Pit Sand
2. River Sand
3. Seas Sand
1. Pit Sand:
 Deposits in soil
 Obtained from pits (excavated from a depth of 1m to 2m from ground level) 
It consists of sharp angular grains
 Free from salts
 Excellent material for mortar and concrete work
2. River Sand
 Obtained from banks or beds of river 
Consists of fine rounded grains
 Color of river sand is almost white
 River sand is usually available in clean condition 
Widely used for all purposes
3. Sea Sand
 Obtained from sea shores
 Consists of fine rounded grains 
Colour is light brown
 It contains salt which attract moisture and hence causes dampness, efflorescence and then leads
to disintegration
  Sea sand also retards the setting action of cement.

Module I Dept. of Civil Engineering, MEAEC

 Due to all such reasons, it is general rule to avoid use of sea sand for engineering purposes
except for filling of basement.

Classification of Sand
According to the size of grains, the sand is classified as fine, coarse and gravelly
(i) Fine Sand : – The sand passing through a screen with clear openings of 1.5875mm
– It is used for plastering purposes
(ii) Coarse Sand : – The sand passing through a screen with clear openings of 3.175mm
– It is used for masonry works
(iii) Gravelly Sand : – The sand passing through a screen with clear openings of 7.62mm
– It is used for concrete works
Bulking of sand:
 The presence of moisture in sand increases the volume of sand. This is due to the fact that moisture
 causes film of water around sand particles which results in the increase of volume of sand.
 The finer the material, the more will be the increase in volume fora given moisture content. This
phenomena is known as the bulking of sand and it can be expressed in a graphical way as shown
in fig.

 When moisture content is increased by adding more water, the sand particles pack near each
other and the amount of bulking of sand is decreased. Thus the dry sand and the sand completely
flooded with water have practically the same volume.

 The bulking of sand affects the volumetric proportioning of sand to a large extent.

 It is more with fine sand and less with coarse sand.

 If proper allowance is not made for the bulking of sand, the cost of concrete and mortar increases
and it results into under-sanded mixes which are harsh and difficult for working and placing.

 A very simple test, as shown in fig. below, may be carried out to decide the percentage of bulking
of sand. Following procedure is adopted:

(1) A container is taken and it is filled two-third with the sample of sand to be tested.
(2) The height is measured, say it is 200 mm.
(3) The sand is taken out of container. Care should be taken to see that there is no loss
of sand during this transaction.
Dept. of Civil Engineering, MEAEC Module I
(4) The container is filled with water.
(5) The sand is then slowly dropped in the container and it is thoroughly stirred by means
of a rod.
(6) The height of sand is measured, say it is 160 mm.
(7) Then, Bulking of sand= (200−160) = 1 25%
160 4

Properties of good sand:

Following are the properties of good sand:
(1) It should be chemically inert.
(2) It should be clean and coarse.
(3) It should be free from any organic or vegetable matter. Usually 3 to 4% clay is permitted.
(4) It should contain sharp, angular, coarse and durable grains.
(5) It should not contain salts which attract moisture from the atmosphere.
(6) It should be well graded i.e. should contain particles of various sizes in suitable proportions.
(7) The fineness modulus of sand should be between 2 and 3.
Function of sand in mortar:
The sand is used in mortar and concrete for the following purposes:
(1) Bulk: It does not increase the strength of mortar. But it acts as adulterant. Hence the bulk or
volume of mortar is increased which results in reduction of cost.
(2) Setting: If building material is fat lime, the carbon dioxide is absorbed through the voids of
sand and setting of fat lime occurs effectively.
(3) Shrinkage: It prevents excessive shrinkage of the mortar in the course of drying and hence the
cracking of mortar during setting is avoided.
(4) Strength: It helps in the adjustment of strength of mortar or concrete by variation of its
proportion with cement or lime. It also increases the resistance of mortar against crushing.
(5) Surface area: It subdivides the paste of the binding material into a thin film and thus more
surface area is offered for its spreading and adhering.
Tests for sand:
Following tests may be carried out to ascertain the properties of sand:
(1) A glass of water is taken and some quantity of sand is placed in it. It is then vigorously shaken and
allowed to settle. If clay is present in sand, its distinct layer is formed at top of sand.
(2) For detecting the presence of organic impurities in sand, the solution of sodium hydroxide or
caustic soda is added to the sand and it is stirred. If colour of solution changes to brown, it
indicates the presence of organic matter.
(3) The sand is actually tasted and from its taste, the presence of salts is known.
(4) The sand is taken from a heap and it is rubbed against the fingers. If fingers are stained, it
indicates that the sand contains earthy matter.
(5) The colour of sand will indicate the purity of sand. The size and sharpness of grains may be
examined by touching and by observing with eye.
(6) For knowing fineness, durability, void ratio, etc., the sand should be examined by the mechanical
analysis.
Substitutes for sand:
In place of sand, other materials such as stone screenings, burnt clay or surkhi, cinders or ashes
from coal, coke dust, etc. may be used to prepare mortar.
The stone screenings are obtained by screening crushed stones. They are sharp and impart more
strength to the mortar. They are generally used in big construction projects like concrete dams,
bridges, etc. where sand in huge quantities is not available near the place of work. They should
however be properly screened to remove the stone dust.

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Module I Dept. of Civil Engineering, MEAEC
The surkhi is the popular substitute for sand. It is obtained by finely grinding burnt clay. It should be
clean and free from any impurities. It plays the same functions as those of sand. But in addition, it
gives strength and improves hydraulic property of the mortar. As it disintegrates under the action of
air and humidity, the mortar with not be used for external plaster or pointing work
Classification of mortars:

The mortars are classified on the basis of the following:

(1) Bulk density
(2) Kind of binding material
(3) Nature of application
(4) Special mortars.
Bulk density:
According to the bulk density of mortar in dry state, there are two types of mortars:
i. Heavy mortars:. The mortars having bulk density of 15 kN/m or more are known as the heavy
mortars and they are prepared from heavy quartz or other sands.
ii. Lightweight mortars: The mortars having bulk density less than 15 kN/m are known as the
lightweight mortars 'and they are, prepared from light porous sands from pumice and other
fine aggregates.
Kind of binding material:
The kind of binding material for a mortar is selected by keeping in mind several factors such as
expected working conditions, hardening temperature, moisture conditions, etc.
According to the kind of binding material, the mortars are classified into the following five categories:
i. Lime mortar:
 In this type of mortar, the lime is used as binding material. The lime may be fat lime or
 hydraulic lime.
 The fat lime shrinks to a great extent and hence it requires about 2 to 3 times its volume of
sand. This mortar is unsuitable for water-logged areas or in damp situations.

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 Dept. of Civil Engineering, Module I
 For hydraulic lime, the proportion of lime to sand by volume is about 1:2 or so. This mortar
should be consumed within one hour after mixing. It possesses more strength and can be
 used in damp situations.
 The lime mortar has a high plasticity and it can be placed easily. It possesses good cohesiveness
 with other surfaces and shrinks very little. It is sufficiently durable, but it hardens slowly.
 It is generally used for lightly loaded above-ground parts of buildings.
ii. Surkhi mortar:
 This type of mortar is prepared by using fully surkhi instead of sand or by replacing half of
sand in case of fat lime mortar. The powder of surkhi should be fine enough to pass BIS No. 9
 sieve and the residue should not be more than 10% by weight.
 The surkhi mortar is used for ordinary masonry work of all kinds in foundation and
superstructure. But it cannot be used for plastering or pointing since surkhi is likely to
 disintegrate after some time.
iii. Cement mortar:
 In this type of mortar, the cement is used as binding material.

 Depending upon the strength required and importance of work, the proportion of cement to
 sand by volume varies from 1:2 to 1:6 or more.
 Sand only can be used to form cement mortar.

 The proportion of cement with respect to sand should be determined with due regard to the
 specified durability and working conditions.
 The cement mortar is used where a mortar of high strength and water-resisting properties is
 required such as underground constructions, water saturated soils, etc.
iv. Gauged mortar:
 To improve the quality of lime mortar and to achieve early strength, the cement is sometimes
 added to it. This process is known as the gauging.
 It makes lime mortar economical, strong and dense. The usual proportion of cement to lime
by volume is about 1:6 to 1:8. It is also known as the composite mortar or lime-cement
 mortar and it can also be formed by the combination of cement and clay.
 This mortar may be used for bedding and for thick brick walls.
v. Gypsum mortar:
 These mortars are prepared from gypsum binding materials such as building gypsum and
anhydrite binding materials.
Nature of application:
According to the nature of application, the mortars are classified into two categories:
(i) Bricklaying mortars: The mortars for bricklaying are intended to be used for brickwork and walls.
Depending upon the working conditions and type of construction, the composition of masonry
mortars with respect to the kind of binding material is decided.
(ii) Finishing mortars: These mortars include common plastering work and mortars for developing
architectural or ornamental effects. The cement or lime is generally used as binding material for
ordinary plastering mortar. For decorative finishing, the mortars are composed of suitable
materials with due consideration of mobility, water retention, resistance to atmospheric actions,
etc.
Special mortars:
Following are various types of special mortars which are used for certain conditions:
(i) Fire-resistant mortar: This mortar is prepared by adding aluminous cement to the finely crushed
powder of fire-bricks. The usual proportion is 1 part of aluminous cement to 2 parts of powder
of fire-bricks. This mortar is fire-resistant and it is therefore used with fire-bricks for lining
furnaces, fire places, ovens, etc.
(ii) Lightweight mortar: This mortar is prepared by adding materials such as saw dust, wood
powder, etc. to the lime mortar or cement mortar. This mortar is used in the sound-proof and
heat-proof constructions.

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Module I Dept. of Civil Engineering, MEAEC
(iii) Packing mortar: To pack oil wells, special mortars possessing the properties of high
homogeneity, water resistance, predetermined setting time, ability to form solid water-proof
plugs in cracks and voids of rocks, resistance to subsoil, water pressure, etc. have to be formed.
The varieties of packing mortars include cement-sand, cement-loam and cement-sand-loam.
The composition of packing mortar is decided by taking into consideration the hydrogeologic
conditions, packing methods and type of timbering.
(iv) Sound-absorbing mortar: To reduce the noise level, the sound-absorbing plaster is formed with
the help of sound-absorbing mortar. The bulk density of such a mortar varies from 6 to 12
kN/m3 and the binding materials employed in its composition may be Portland cement, lime,
gypsum, slag, etc. The aggregates are selected from lightweight porous materials such as
pumice, cinders, etc.
(v) X-ray shielding mortar: This type of mortar is used for providing .the plastering coat to walls
and ceiling of X-ray cabinets. It is a heavy type of mortar with bulk density over 22 kN/m3. The
aggregates are obtained from heavy rock and suitable admixtures are added to enhance the
protective property of such a mortar.
Grades of mortar
Mortars are specified by different grades as per I.S. Code in terms of minimum compressive strength
at 28 days. These grades have some relation with the proportion of ingredients. Normally mortars are
specified by its ratio like 1:3 or 1:4 and so on. 1:3 mix means for one part of cement 3 parts of sands
by volume. Some typical grades given below.
Grade Mortar Mix Compressive Strength
MM 1.5 1:7 1.5 to N/mm2
MM 3 1:6 3 to 5 N/mm2
MM 5 1:5 5 to 7.5 N/mm2
MM 7.5 1:4 and 1:3 Above 7.5 N/mm2

Table: Selection of Cement Mortar

Sl. Mortar proportion
Type of construction
No Cement: Sand
1. In waterlogged areas and exposed conditions 1:3
2. DPC and Rigid pavements 1:2
3. General RCC works 1:3
4. Internal Walls and surfaces (less temperature) 1:3
5. Fire Bricks laying 1:2
6. Partition walls and parapet walls 1:3
7. Plaster work 1:3 or 1:4
8. Pointing work 1:2 or 1:3
9. Reinforced Brick work 1:3
10. Stone masonry work 1:2

Properties of good mortar mix and mortar:

Following are the properties of a good mortar. ,
 It should be capable of developing good adhesion with the building units such as bricks,
 stones, etc.
 It should be capable of developing the designed stresses.
 It should be capable of resisting penetration of rain water.
 It should be cheap.
 It should be durable.
 It should be easily workable.

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 Dept. of Civil Engineering, MEAEC Module I
 It should not affect the durability of materials with which it comes into contact.
 It should set quickly so that speed in construction may be achieved.

 The joints formed by mortar should not develop cracks and they should be able to maintain
their appearance for a sufficiently long period.
General uses of mortar
Mortar has the following uses.
 Mortar is used to provide the joints for brick and stone masonry.
 It is used for plastering walls and for pointing masonry work.
 It provides an even bedding layer for placing building units.
  Pipe joints may be closed by mortar.
 Plastering improves the appearance.
 Plaster may be used to make moulds for coping, comice etc.
 Open joints in brickwork and stonework can be hidden by plaster.
 Cracks detected in walls can be filled by plaster.

TIMBER PRODUCTS
Any wood which is used in engineering works is defined as Timber. Although some of its usages are
given up to steel, concrete and other products its usages in construction and other commercial
purposes are still of great importance. Nowadays, wood is extensively used for walls and floors of
buildings, carpentry and graded plank items and prefabricated standard wooden cottages.

The use of fibre board, ply-boards in building practice provides a substantial saving both in capital
investments and running costs. The use of boards made of pressed wood shavings in dwelling house
construction has a great economical effect.

MARKET FORMS OF TIMBER

1. Board

Board is a timber piece with parallel sides having thickness of about 50 mm and its width is more than
200 mm. Wood boards are available in a various sizes, types, species and grades. These types and
grades are based on dimensions, qualities, appearances and functions of boards. When wood boards
are assembled in bulk they are referred to as units, bunks or lumber.
Types of Boards
(a) Rough Board
Rough Boards cut from the tree with a large band saw and kiln dried to about 14% moisture. Its
thickness varies from 5/8 to 1 inch. The advantage of the rough board is less in cost.
(b) Planned Board
Planned wood boards are the most common type of wood boards and planned (or smooth
surfaced) down to specific dimensions such as 5/16 or 13/16 inch.
(c) S4S Boards (Sanded on 4 Sides)
Sanded Boards (or S4S) means that the board is completely sanded on four sides and is ready to finish.
This board has been milled down to exact sizes, typically 3/4-inch thick with random lengths.

2. Batten
Batten is a timber piece or a strip of solid material made from wood with thickness and width is less
than 50 mm. Battens used in construction are,
 Roofing battens
 Wall battens
 Battens as spacers
 Batten trim
 Board-and-batten
CE 204 – Construction Technology 1.7 | Page
Module I Dept. of Civil Engineering, MEAEC
 Batten doors

3. Deal is a timber piece of soft wood with parallel sides having thickness of about 50 mm to 100
mm and width is not more than 240 mm.
4. Plank is a timber piece of soft wood with parallel sides having thickness less than 50 mm and
width is more than 50 mm.
5. Log is the trunk of the tree obtained after removal of branches.
6. End is the short piece of Batten, Deal and Scantling etc.
7. Pole or Spar is a sound long log of wood and its diameter does not exceed 200 mm.
8. Quartering is a square piece of timber, the length of side being 50 mm to 150 mm.
9. Scantling is a timber piece whose breadth and thickness exceed 50mm and less than 200 mm in
length. These are the pieces of miscellaneous sizesof timber sawn out of a log. Scantling is a
timber beam of small cross section.
10. Baulk is a roughly squared timber piece and it is obtained by removing bark and sap wood. One
of the cross-sectional dimensions exceeds 50 mm, while the other exceeds 200 mm.
INDUSTRIAL TIMBER
Industrial Timber is defined as the timber prepared in a factory with specifications and having shape,
appearance, strength etc.
Following are the some of the industrial timber.
1. Veneers
Veneers are thin sheets or slices of wood of superior quality and its thickness varies from 0.4 mm
to 0.6 mm. The maximum thickness of the veneer is limited to 1 mm. The most suitable wood for
veneers is Walnut.
2. Plywoods
An odd number of layers of wood or veneers are arranged and glued by using glues under
pressure is called plywood.
3. Fibre Boards
4. Thermacole
Thermacole is a well-known product of heat insulating material provides good insulation.
Thermacole is a light and cellular plastic material used for sound and heat insulation of ceiling,
walls and refrigerators and for air conditioning of the buildings
5. Panels of laminates
Laminated (or Lamin) boards have a core of strips, each not exceeding 7 mm in thickness. The
edges are glued together to form a solid sheet, which is then glued between two or more outer
veneers. The wooden strips may be obtained from small round wooden legs.

PLYWOODS
Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued
together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is
an engineered wood from the family of manufactured boards which includes medium-density
fibreboard (MDF) and particle board (chipboard).
An odd number of layers of wood or veneers are arranged and glued by using glues under pressure is
called plywood. The outer most veneer sheets in a plywood panel are called faces of plywood.
The interior plies which have their grain directions parallel to that of the faces are termed as core or
centre. Other piles which have grain directions perpendicular to that in the face are termed as cross
bands.
Types of Plywood
1. Softwood plywood

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Dept. of Civil Engineering, MEAEC Module I
2. Hardwood plywood
3. Marine plywood
Softwood Plywood

Softwood panel is usually made either of spruce, pine, and fir

(collectively known as spruce-pine-fir or SPF) and is typically used for
construction and industrial purposes including sheathing, roofing,
sub-flooring, crating, and packaging.

The number of plies depends on the thickness and grade of the sheet but
at least three are required as the minimum odd number of plies.
Plywood for sub-flooring applications is often tongue and groove; this
prevents one board from moving up or down relative to its neighbor,
this provides a solid feeling floor when the joints do not lie over joists.

Hardwood plywood

Hardwood plywood as a manufactured panel made up of three or

more thin plies of hardwood (ie. red oak), laid on top of each
other, with the grain of each ply running perpendicular to the one
on either side of it. Plywood offers a strong, inexpensive, and
environmentally responsible alternative to its solid wood
counterparts.

Types of Plywood like substrate such as Veneer Core, MDF, or

Particleboard are typically faced with hardwood species, including
cherry, walnut, ash, white oak, red oak, birch, maple, mahogany,
rosewood, teak, and a large number of other species.
Marine plywood
Marine plywood is manufactured from durable face and core
veneers, with few defects; so it performs longer in both humid and
wet conditions and resists delaminating and fungal attack. Its
construction is such that it can be used in environments where it is
exposed to moisture for long periods. Each wood veneer will be
the same species throughout (Fir, Okoume, and Meranti), and have
minimal core gap, limiting the chance of trapping water in the
plywood and hence providing a solid and stable glue bond. It uses
an exterior Water and Boil Proof (WBP) glue.
Marine plywood is frequently used in the construction of boats, docks, outdoor signs, counter top
underlayment, and anywhere that requires prolonged exposure to outdoor elements.
Advantages of Plywood
Following are the advantages of plywood.
1. Plywood can be curved into desired shapes.
2. It can be formed into any desired colour.
3. It has good moisture resistance
4. It has good strength along the grains and across the grains.
5. The shrinkage and swelling of plywood is highly reduced because the piles are arranged at right
angles to each other.
6. It has better splitting resistance due to the grains in adjacent veneers in cross direction as
such nailing can be done very safely even near the edges.
7. They have good tensile strength in all the direction.

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Module I Dept. of Civil Engineering, MEAEC
8. They are very easy to work and can be made to suit any design.
9. They are light in weight.
10. It has good atmospheric resistance
Uses of Plywood
These are extensively used for partitions, ceilings, doors, concrete form work, plywood boards,
laminated boards and block boards (built-up boards) etc. Laminated Boards are built-up boards with
core strips up to 7 mm wide and 7 mm thick and block boards are built-up boards of plywood.

PANELS OF LAMINATES
The grains directions of the core block run at right angles to that of the adjacent outer veneers.
These boards are extensively used for railway carriages, bus bodies, marine and river crafts, furniture
partitions, panelling, prefabricated houses etc. Fibre boards are built up from wood or vegetable
(wood wastes, waste paper, agricultural wastes, etc.) are classified by the process of their moulding.
If the boards are moulded by wet process, the main bond is by the felting of woody fibres and not by
added glue. For the boards moulded by dry process, the bond between the pre-dried fibres is
improved by adding 4% to 8% of synthetic resin. For better performance wood preservatives and
other admixtures are often added to the pulp.
Insulating boards are not compressed during manufacture. Fibre boards are manufactured in various
densities like soft, medium and hard. The soft boards are used for walls and ceilings. Medium boards
find their application in panelling, partition walls, doors and windows. Hard boards have one surface
smooth and the other one textured. These have higher densities, higher mechanical properties and
improved moisture and termite resistances. The strength and weather properties of hard boards can
be improved by oil tempering and such boards are called Tempered Hard Boards. Some of the trade
names of hard boards are Masonite, Celotex, Essex boards etc.
Batten Boards and Lamin Boards
Batten boards have core made up of 80 mm wide wood pieces as
shown in Figure forming a slab glued between at least two surface
veneers. Whereas, Lamin boards have a core of strips, each not
exceeding 7 mm in thickness, as shown in Figure glued together to
form a slab which in turn is glued between two or more outer
veneers. The directions of the grains of the core block run at right
angles to that of the adjacent outer veneers.

PARTICLE BOARD
Particle Board (or Chipboard or Medium Density Fibre - MDF Board) is an engineered wood product
manufactured from wood chips, sawmill shavings or sawdust with a synthetic resin or other suitable
binder, which is pressed and extruded. Particle Boards are made from gluing together small chips and
saw-dust and firmly pressing them together to make boards or sheets. (Oriented strand board, also
known as flake board and wafer board, is similar but used machined wood flakes offering more
strength. All of these boards are composite material that belongs to the spectrum of fibre board
products.)
Manufacturing of Particle Board
The manufacturing of particleboard is described below.
1. Particleboard or chipboard is manufactured by mixing wood particles or flakes together with a
resin and forming the mixture into a sheet.
2. The raw material to be used for the particles is fed into a disc chipper with between four and
sixteen radially arranged blades (The chips from disk chippers are more uniform in shape and
size than from other types of wood chipper). The particles are then dried, after which any
oversized or undersized particles are screened out.
3. Resin is then sprayed through nozzles onto the particles. There are several types of resins that are
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 Dept. of Civil Engineering, MEAEC Module I
commonly used. Following resins are used.
 Amino Formaldehyde
 Urea Melamine Resins
  Phenolic Resins
 Melamine Urea Phenolic Formaldehyde
 Phenolic Resins

4. The liquid mixture is made into a sheet, after the resin has been mixed with the particles.
5. The sheets formed are then cold-compressed to reduce their thickness and make them easier to
transport.
6. This process sets and hardens the glue. All aspects of this entire process must be carefully
controlled to ensure the correct size, density and consistency of the board.
7. The boards are then cooled, trimmed and sanded. They can then be sold as raw board or
surface improved through the addition of a wood veneer or laminate surface.

Characteristics of Particle Board

Following are the characteristics of particle board.
1. Particle board is cheaper, denser and more uniform than conventional wood
2. Particle board can be made more attractive by painting or the use of wood veneers onto
surfaces that will be visible.
3. It is the lightest and weakest type of fiberboard, except for insulation board.
4. Particle boards are not much stronger and denser than the Medium density fibre board and
hard board (also called High-Density Fibre Board).
5. Different grades of particleboard have different densities.
Classifications of Particle Board
Particle Boards are classified based on the density and as follows.
3
1. Low density (less than 400 kg/m )
3
2. Medium Density (between 400 and 900 kg/m )
3
3. High Density (between 900 and 1200 kg/m )
Advantages of Particle Board
Following are the advantages of particle board.
(a) Low Cost
The main advantage of particle board (over solid wood or plywood) is that its cost is very
low. Compared to plywood furniture of similar dimensions, particle board furniture costs less
than half. (This low cost is due to because particle boards are not as durable as plywood or
solid wood)
(b) Ready-made furniture
Particle boards are machine manufactured to desired dimensions, and thus standard pieces
of furniture can be produced using these boards.
(c) Pre-laminated boards
A thin layer of lamination (decorative laminate) is usually glued over the surface of the particle
boards at the time they are manufactured and these are called pre-laminated boards. Lamination
increases the beauty as well as the durability of the board to some extent.
(d) Light in weight
Particle boards are very light in weight, and hence furniture made from these boards is
relatively easy to transport.

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Module I Dept. of Civil Engineering, MEAEC
Disadvantages of Particle board
The disadvantages of particle board are listed below.
(a) Low Strength
It is an important drawback which is that the board is not as strong as other types of wood. It is
less dense and can easily get damaged while handling.
(b) Less Durability
Particle boards are also getting damaged due to moisture and humidity. This means that
furniture made from these boards will not last very long. A major disadvantage of particleboard
is that it is very prone to expansion and discoloration due to moisture, particularly when it is not
covered with paint or another sealer.
(c) Cannot Support Heavy Loads
Particle boards are not used in applications where the boards will be subjected to heavy
weights. Being low on strength, particle boards are only suitable for holding low weights or as
forming the walls of cabinets and the like.
(d) Not as Eco-friendly as Solid Wood Furniture
Particle boards are made from small particles of wood such as sawdust and small chips which
are glued and pressed together to form a sheet. The glue used is a plastic resin (phenolic resin),
the same that is used in the making of decorative laminates. This is not as eco-friendly as using
good quality solid wood furniture that is 100% natural.
Applications
These are widely used in buildings, partitions, ceilings, floor slabs, doors, furniture etc.

FIBRE BOARD
Fibre board is a type of engineered wood product that is made out of wood fibres.
Various types of fibre boards (in order of increasing density) are,
 Particle Board
 Medium Density Fibre
 Board Hard Board
Fibre board is sometimes used in the name of particle board, but particle board usually refers to
low-density fibre board. Plywood is not a type of fibre board, as it is made of thin sheets of
wood, not wood fibres or particles.
Fibre board, particularly medium-density fibre board (MDF), is heavily used in the furniture
industry. Fibre board is also used in the auto industry to create freeform shapes such as
dashboards, rear parcel shelves and inner door shells. These pieces are usually covered with a
skin, foil or fabric such as cloth, suede, leather or polyvinyl chloride.
Types of Fibre Board
Depending upon their form and composition, they classified as insulating boards, medium hard
boards, hard boards, super hard boards and laminated boards. They are also available under
various trade names such as Euraka, Indianite, Insulite, Masonite, Nordex, Treetex, etc.
1. LDF (low density fibre board) - density less than 650 kg / m3.
2. MDF (medium density fibre board) - density from 650 to 800 kg / m3.
3. HDF (high density fibre board) - density over 750 kg / m3
Properties of Fibre Board
• These are rigid boards, the thickness varries from 3mm to 12mm
• They are available in lengths varying from 3m to 4.5m and in width varying from 1.20m to
1.80m
• The maximum and minimum limits of weight are respectively 9600 N/m³ and 500 to 600
N/m³.
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Dept. of Civil Engineering, MEAEC Module I
• The weight of fibre boards depending upon the pressure applied during manufacturing.
• Fibre board has a hard, flat, smooth surface
Uses and Applications of Fibre Board
• For internal finish of rooms such as wall panelling, suspended ceiling etc.
• To construct form work for concrete i.e, to retain cement concrete in position when it is
wet.
• To construct partitions.
• To prepare flush doors, tops of tables, etc.
• To provide an insulating material of heat and sound.
• To work as paving or flooring material.
• The hard boards are suitable for polish and varnish
COMPARISON BETWEEN PLYWOOD, FIBRE BOARD AND PARTICLE BOARD
Following table shows the difference between Fibre board and Particle board.
Table: Difference between Plywood, Fibre Board and Particle Board

Sl.No Factor Plywood Fibre Board Particle Board

Engineered wood It is a waste-wood
Plywood is made composite, made product made by
Base
1. using hardwood up of wood fibers heat pressing
Material
veneers (no visible wood wood chips,
grain, rings, or sawmill shavings
High (700 to 720 Low to high (200 to
2. Density 3 3
kg/m ) 950 kg/m )
3. Strength High High (10 MPa) Low
Sagging effect
4. High Low High
when loading
5. Splitting High Low High
6. Cost High High Low
Suitable for
Suitable for Ready -
7. Suitability aesthetic purpose
Made Furniture
and furniture
Process of
8. Handling and Easy Easy Satisfactory
Painting etc

IRON AND STEEL

The steel is a ferrous material containing a maximum of 1.5% of carbon in its composition. Steel is
harder and tougher than iron (cast-iron, wrought iron etc.) because its carbon chemically combines
with complete iron, exist in its free state.
The cast iron can take only the compressive loads and the wrought iron can take only the tensile loads.
Steel replaces both the cast iron and wrought iron.
Based on the carbon content, steel is classified as follows
Low Carbon Steel - Less than 0.15%
Mild Steel - 0.15 to 0.3
Medium Carbon Steel - 0.3 to 0.8
High Carbon Steel - 0.8 to 1.5%
Hard Steel - more than 1% - (called Tool Steel or Cast Steel

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Module I Dept. of Civil Engineering, MEAEC
PROPERTIES OF STEEL
Properties of steel highly depend on the carbon content and percentage of impurities present
in the steel. Following are the detailed discussion of properties of mild steel and hard steels.
Properties of Mild Steel
Following are the properties of mild steel.
1. Its specific gravity is about 7.80.
2. Its melting point is about 1400°C
3. It can be magnetized permanently.
4. It can be readily forged and welded.
5. It is malleable and ductile.
6. It is not easily attacked by salt water
7. It is tougher and more elastic than wrought-iron
8. It can be used for all types of structural work.
9. It corrodes easily and rapidly.
2
10. Its ultimate compressive strength is about 80 to 120 kN/cm
2
11. Its ultimate tensile and shear strengths are 60 to 80 kN/cm
12. It cannot be easily hardened.
13. It has fibrous structure.
Properties of Hard Steel
Following are the properties of hard steel.
1. Its melting point is about 130° C.
2. Its specific gravity is 7.90.
2
3. Its ultimate compressive strength is about 140 to 200 kN/cm
2
4. Its ultimate shear strength is about 110 kN/cm
2
5. Its ultimate tensile strength is about 80 to 110 kN/cm
6. It can be easily hardened and tempered.
7. It can be magnetized permanently.
8. It cannot be readily forged and welded.
9. It has granular structure.
10. It is not easily attacked by salt water.
11. It is tougher and more elastic than mild steel.
12. It is used for finest cutlery, edge tools and for parts which are to be subjected
to shocks and vibration.
13. It rusts easily and rapidly.
Properties of High Carbon Steel
The carbon content in high tensile steel is 0.6 % to 0.8%, Manganese 0.6%, Silicon 0.2%,
Sulphur 0.05% and Phosphorus 0.05%.
1. It is also known as high strength steel.
2
2. The ultimate tensile strength is about 2000 N/mm .
3. The minimum elongation of high carbon steel is 10 %
4. High Tensile steel can be used for pre-stressed concrete construction.
FACTORS AFFECTING THE PROPERTIES OF STEEL
Various Physical properties are highly affected by the following three factors.
1. The carbon content in steel influences the hardness and strength of the steel and
ductility.
2. Presence of impurities like Silicon, Sulphur, Phosphorus and Manganese are some of
the impurities present in the steel.

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 Dept. of Civil Engineering, MEAEC Module I
3. The properties of steel vary with various processes of heat treatments like hardening,
annealing etc.

REINFORCING STEEL
Reinforcing steel bars are the steel reinforcements, used in the concrete to withstand tension
forces. In general, concrete is sufficiently strong to withstand the compression forces, however
weak in carrying tensile force. Tensile forces in concrete can crack concrete. In order to overcome
this effect, steel reinforcing bars (called Re-bars) are used in the concrete.
Steel as reinforcement
Steel bars are also used to carry compression in beams and columns. For any material to be used as
reinforcement for concrete, it should possess the following properties
1. It should have high tensile strength.
2. It should be able to develop a good bond with concrete.
3. It should possess a high modulus of elasticity.
4. It should have the same (or nearly the same) temperature coefficient of expansion and
contraction as concrete to avoid the development of thermal stresses.
5. It should be easily available.
Materials like asbestos, glass, bamboo cane, etc., were tried on experimental basis as reinforcement
but were found unsuitable. Steel is a material which satisfies all the above requirements and is
successfully used as reinforcement. Combination of concrete and steel is ideal because when
concrete sets, it contracts and thus, it grips the reinforcement. Because of this bond, steel and
concrete can work together as a single material.
REINFORCING STEEL-TYPES
Different types of reinforcement used are,
 Mild Steel and Medium Tensile steel bars, confirming to IS:432
 High Yield Strength Deformed Steel (HYSD) Bars, confirming to IS:1786
 Cold Twisted Deformed (CTD) Bars
  Thermo Mechanically Treated (TMT) Bars
 Hard drawn steel wires fabric, confirming to IS: 1566
 Structural Steel wire, Grade A of confirming to IS:2062
 Corrosion Resistance Steel, etc.
2
In all cases the modulus of elasticity of steel shall be taken as 200 kN/mm .
Mild Steel and Medium Tensile steel bars
Mild steel bars have been widely used as reinforcement in construction industry. The yield
2
strength of mild steel is 250 N/mm (minimum specified value). Among all kinds of steel, mild
steel is the most ductile.
Mild steel can be used as plain or deformed bars, to
increase the bonding ability. Twisting produces
deformations on the surface of the steel bar, which
increases its bond with concrete. The deformed bar is
one which is provided with lugs, ribs or deformations
on the surface of the bar to minimize the slippage of
the bar in concrete so that its bond strength exceeds
that of a plain bar of the same size by 60 percent or
more. The permissible stresses for deformed mild
steel bars are the same as for plain mild steel bars except for bond stress, where permissible bond
stress can be increased by 60 percent in case of deformed bars. The mass of steel reinforcement shall
3
be calculated by considering unit mass of steel equal to 7850 kg/m .

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Module I Dept. of Civil Engineering, MEAEC
HYSD - Cold Twisted Deformed (CTD) Bars
When the mild steel plain bars are subjected to cold working by tensioning and twisting, CTD bars are
obtained. Tensioning raises both the yield as well as the ultimate strength of steel.
In India, the CTD bars are available in the trade names of TOR steel, Tistrong, Tiscon, GIRP, etc. These
bars are available in three grades, Fe 415, Fe 500 and Fe 550. In practice three types of steel
reinforcement are normally used. They are: mild steel reinforcement, high yield strength deformed
bars of grade Fe 415 and Fe 500, where Fe denotes ferrous materials and number, the yield strength
2
of steel in N/mm .
HYSD - Thermo Mechanically Treated (TMT) Bars
The Thermo-Mechanically Treated (TMT) bars are manufactured by subjecting the hot rolled M.S. bars to a
controlled cooling process which converts the outer surface of the bar into hardened structure. The
subsequent cooling allows the hot inner core to soften the outer surface through thermal exchange
resulting into tempered martensite in the peripherical zone and a fine grain ferrite-pearlite at the central
zone. This process increases the yield strength of the bar without losing its yielding property.
TMT bars are manufactured in three grades, viz., 400, 500 and 550 having I characteristic yield
2 2 2
strength of 400 N/mm , 500 N/mm and 550 N/mm and are available in limited variety of
diameters (8,10,12,16,20,25 mm).
Hard-drawn steel wire fabric
These are made in two types, square mesh and oblong mesh. It consists of longitudinal and
transverse wires at right .angles to one another joined by resistance I spot welding. This
reduces the cost of labour and fabrication in the field. The mesh i is available in diameters
from 3 to 10 mm, the diameters being same in both the directions. Both the directions can
serve as main reinforcement. Usually these meshes are employed as slab reinforcement.
Corrosion Resistance Steel
Recently, corrosion-resistant steel has been developed and is being used in aggressive environments,
marine structures, etc. These steels have the same usual grades, Fe 415, Fe 500 and Fe 550 as per
BIS specifications. In addition, they are coated with corrosion-resistant elements.
REINFORCING STEEL - SPECIFICATIONS
Reinforcing steel is specified by its tensile strength. For design purpose, IS: 456-2000 classifies the
reinforcing steel into four grades based on its strength, as follows.
• Mild Steel - Grade I -Fe250
• Medium Tensile steel - Grade I - Fe 350
• High Strength Deformed Steel - Fe 415
• High Strength Deformed Steel - Fe 500
Various forms of bars are,
Round Bars
These are the bars with circular sections available in diameter varying from 5mm to 25mm and
weight per meter length are 1.5 N and 38 N. Used for the construction of steel grill work, window
and gates etc. and as reinforcement in RCC works.

Fig. Round Bars High Yield

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Dept. of Civil Engineering, MEAEC Module I
Strength Deformed (HYSD Steel)
High Yield Strength Deformed steel has strength of 415 MPa. These materials have projections on
their surface and are produced by the cold twisting of deformed bars. Due to the presence of the
ribs on the surfaces, the yield strength, bond strength, tensile strength is improved.
Tor steel
The most commonly used reinforcement in RCC is Tor steel the other names are deformed steel bar,
HYST bar and CWD bar. Tor steel is used for the construction of reinforcement in RCC works for
road, bridges, dams etc.
As per IS 1786 - 1985, the carbon content in reinforcement steel shall not exceed 0.3%.The mass per
running metre of mild steel and that of HYSD reinforcement of the same diameter is the same.

Market Available Forms of Steel:

Fe415 is a grade of High Strength Deformed Steel Bar for Concrete Reinforcement. This
Grade has been specified by Bureau of Indian Standards (BIS) in a documented standard IS
1786:2008, which is a revised version of IS 1786:1985.The number 415 usually denotes the
minimum Yield Strength (in N/mm2) of the Bar to qualify as Fe415.There are total 7 Grades
specified in the standard (IS 1786), which are:

1. Fe415
2. Fe415D
3. Fe500
4. Fe500D
5. Fe550
6. Fe550D
7. Fe600
Now it is clear that what minimum Yield Strength of the Bar should be to qualify as that
Grade. Grades with “D” denotes more Ductile Grades. Where minimum Tensile Strength
required should be 8% more than Yield Strength for Grades without “D”, it should be
10% more than Yield Strength to qualify as a “D” Grade.

2
Fe250: Yield Stresses or Yield strengths for MS bars = 250 N/mm . These are thus known
as Fe 250 Grade bars also. For these bars, the permissible tensile & compressive stresses
for design purposes are specified to be 140 & 130 N/mm2 by IS-432, depending on type of
members

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Module I Dept. of Civil Engineering, MEAEC
Advantages and Use of Reinforcing Steel:

1. Compatibility with concrete – Reinforcing steel does not need to be tied directly to the
formwork and does not float in concrete
2. Robustness – Reinforcing steel is robust and able to withstand rigors of construction.
3. Ability to be recycled – Reinforcing steel is able to be readily recycled at the end of
the structure design life.
4. Ability to be bent – Reinforcing steel can be bent after being manufactured. This simplifies
the construction and provides for rapid delivery of fabricated materials.
5. Availability – Reinforcing steel is available in every region of the country. Due to the
number and distribution of plants, LEED and other sustainability credits are available.
6. These bars can be welded.
7. These can be used for major reinforcement works.
8. It has better structural properties.
9. These can be bend for 180° without any cracks.

STRUCTURAL STEEL
Steel, used as members in load-bearing frames in buildings, and as members in trusses, bridges, and
space frames are called Structural steel. In steel buildings, claddings and dividing walls are made up
of masonry or other materials and often a concrete foundation is provided.
Steel is also used in conjunction with concrete in composite constructions and in combined frame
and shear wall constructions, due to its high strength, speed of erection, prefabrication, and
demountability.
In many cases, the fabrication of steel members is done in the workshop and the members are then
transported to the site and assembled. Tolerances specified for steel fabrication and erections are
small compared to those for reinforced concrete structures. In addition to this, welding, tightening of
high-strength friction grip bolts, etc., require proper training. Due to these factors, steel structures
are often handled by trained persons and assembled with proper care, resulting in structures with
better quality.
Steel offers much better compressive and tensile strength than concrete and enables lighter
constructions. Also, unlike masonry or reinforced concrete, steel can be easily recycled. However,
steel requires fire and corrosion protection.
TYPES OF STRUCTURAL STEEL
1. Carbon steel (IS 2062)
Carbon and manganese are the strengthening elements in Carbon steel. The specified minimum
ultimate tensile strength for these steels varies from about 410 to 440 MPa. The specified minimum
yield strength varies from about 230 to 300 MPa (Table 1 of IS 800: 2007).
2. High-strength carbon steel
High-strength steel has high carbon content and it reduces the ductility, toughness, and weldability.
This steel is specified for structures such as transmission lines and microwave towers, where
relatively light members are joined by bolting. Such steels have a specified ultimate tensile strength,
ranging from about 480-550 MPa, and a minimum yield strength of about 350-400 MPa.
3. Medium and high strength micro-alloyed steel (IS 8500)
Even though, this steel contains less carbon, achieves high strength due to the addition of alloys such
as niobium, vanadium, titanium, or boron (total microalloying elements restricted to less than
0.25%). This steel has a specified ultimate tensile strength ranging from 440 to 590 MPa and a
minimum yield strength of about 300-450 MPa.
4. High-strength quenched and tempered steels

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Dept. of Civil Engineering, MEAEC Module I
These are heat treated steels, to develop high strength. Though they are tough and weldable, they
require special welding techniques. They have a specified ultimate tensile strength between 700 and
950 MPa and minimum yield strength between 550 and 700 MPa.
5. Weathering steels
These are low-alloy atmospheric corrosion-resistant steels, which are often left unpainted (see
Section 15.3 for the details of these steels). They have an ultimate tensile strength of about 480 MPa
and a yield strength of about 350 MPa.
6. Stainless steels
These are low-carbon steels contains a minimum of 10.5% (maximum 20%) chromium and 0.50%
nickel.
7. Fire-resistant steels (Thermo-Mechanically Treated)
TMT steels, they perform better than ordinary steel under fire.
ADVANTAGES OF STEEL AS A STRUCTURAL MATERIAL
1. High strength - On the basis of strength/weight ratio, steel is at least 3.5 times more efficient
than concrete.
2. High ductility - In structures built with structural steel, overloading does not cause problems.
Another advantage of structural steel’s ductility, is that when highly overloaded (like earthquakes),
the large deflections give visible evidence of impending failure.
3. Uniformity - The quality of steel-intensive construction is invariably superior, when compared
with that of construction involving other materials.
4. Environment-friendly - Structural steel is recyclable and environment- friendly. Over 400 million
tonnes of steel are recycled annually worldwide, which represents 50% of all steel produced.
5. Versatility - Using structural steel, it is possible to fasten different members together by simple
connection techniques such as welding, bolting, and riveting. Steel members can also be
rolled into a wide variety of sizes and shapes.
6. Prefabrication - Often, steel components are manufactured at the factory,
transported to the site, and erected using bolting and a minimum amount of welding.
7. Permanence - Several structures are available to testify to the durability of steel
structures (The Eiffel Tower and the Railway Bridge across the Firth of Forth, both built
in 1890, using structural steel). Under certain conditions, weathering steels do not
require any painting or maintenance.
8. Additions to existing structures - The repair and retrofit of steel members and their
strengthening at a future date are simpler than in concrete members.
9. Least disturbance to the community - Steel-intensive construction causes the least
disturbance to the community in which the structure is located.
10. Fracture toughness - Structural steels are tough (the ability of a material to absorb
energy in large amounts is called toughness). Due to its toughness and ductility, steel
members can be subjected to large deformations.
11. Elasticity - Steel behaves closer to design assumptions than most materials because it
follows Hooke's law up to fairly high stresses. The moments of inertia of steel members
can be definitely calculated.
DISADVANTAGES OF STEEL AS A STRUCTURAL MATERIAL
1. Corrosion - Maintenance costs - Most steels are susceptible to corrosion when freely
exposed to air and water, and must therefore be periodically maintained. However,
weathering steels do not need to be painted. Steel members in the interior of buildings
(not exposed to rain) do not corrode quickly.
2. Fireproofing costs: The strength of the steel is highly reduced at sudden
temperatures. Since steel is an excellent heat conductor, non-fireproofed steel members
may transmit enough heat from a burning section or compartment of a building to ignite
materials which come into contact with them in adjoining sections of the building.

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Module I Dept. of Civil Engineering, MEAEC
3. Susceptibility to buckling - The longer and more slender the compression member, the
greater is the danger of buckling. Though steel has a high strength per unit of weight, steel
columns have to be stiffened against buckling.
4. Fatigue - Another undesirable property of steel is that its strength may be reduced if it is
subjected to a large number of stress reversals or several variations of tensile stress.
TYPES AND USES OF STEEL STRUCTURES
Various steel structures are classified based on its usage, as follows.
1. Buildings
These may include rigid, semi-rigid, or simple connected frames, load-bearing walls, cable-stayed and
cantilevered structures. Buildings may be simple or multi-storeyed, with single or many spans.
For multi-storeyed buildings, several lateral bracing systems have been developed, such as trussed,
staggered truss, rigid central core, etc. These buildings may include a steel frame as shown in Figure
or have a steel roof supported by load-bearing walls.
2. Bridges
Bridges may be classified as truss, plate-girder, arch, cantilever, cable-stayed, or suspension etc. (using
cables or rods as principal load-carrying members). The truss and plate-girder bridges are commonly
adopted for small to moderate spans and cable-stayed and suspension bridges for long spans.
3. Towers
Towers may be of different types, such as lighting towers, power transmission towers, observation
towers, towers for radar and TV installation, telephone relay towers and windmill towers. Towers
may be self-supporting or cable-stayed. Most towers are made of steel angles or tubes, which are
bolted at site.
4. Storage tanks
They may be rectangular, circular, or spherical. They can be used to store oil or water. They may
rest on the ground or be elevated on a staging.
5. Other structures
Silos, bunkers, domes, folded plates, offshore platforms, chimneys, cooling towers. In addition to
these structures, the structural engineer may be called upon to design ships, parts of various
machines and other mechanical equipment, and automobiles (bus and car bodies, chassis), etc.

Fig. Types of Steel Structures

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SPECIFICATIONS OF STRUCTURAL STEEL
I.S Hand Book No. 1 published by the Bureau of Indian Standards provides the dimensions, weights
and geometrical properties of various sections. Following are the standard shapes of rolled steel
sections available in the market.
Angle Section
An angle-section is designated by its leg lengths and thickness. For example, I.S.A.40 x 25 x 6 mm
means, the section is an unequal angle with legs 40 mm and 25 mm in length and thickness of the
legs 6 mm. Angle sections were probably the first shapes rolled and produced in 1819 in America.
The angle section may be equal legs are unequal legs as shown in Fig. 1.8.
The angles of equal legs are varying from 20 mm x 20 mm x 3 mm to 200 mm x 200 mm x 25 mm.
The corresponding weights per unit length are 9 N and 736 N respectively. The unequal legs are
varying from 30 mm x 20 mm x 3 mm to 200 mm x 150 mm x 1 mm. The corresponding weights per
unit length are 11 N and 469 N respectively.
The angle sections are extensively used in the structural steelwork especially in the construction
of steel roof trusses and filler joist floors.

Fig. Equal and unequal angle sections

Channel Section
Channel sections have a web with two equal flanges. A Channel section
is designated by the height of the web and the width of the flange.
Channel sections are available in sizes from 100 mm x 45 mm to 400 mm
x 100 mm with weight 58 N/m and 494 N/m respectively. Channel
sections are used for the construction of steel built in columns, beams,
steel bridges etc.

T - Section
T section consists of web and flange. It is designated by the overall depth
and width. T section is available in sizes from 20 mm x 20 mm x 8 mm to
150 mm x 150 mm x 10 mm and their weights are 9 N/m and 228 N/m
respectively. T section is used for the construction of steel built up
sections, chimneys, steel bridges etc.

I- Section
I-section are commonly known as Rolled Steel Joists (RSJ). I-section consists
of a web and two flange. It is designated by the overall depth of flange and
weight per meter length. It is available in sizes from 75 mm x 50 mm to 600
mm x 210 mm with weight 61 N/m and 995 N/m respectively. It is used for
the construction of columns, beams, grillage foundations etc. Unequal I
section are used as rails.

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Expanded Metal
This form of steel is available in different shapes and sizes.
It is prepared from sheets of mild steel, which are
machine cut and drawn out or expanded. A diamond
mesh appearance is thus formed throughout the whole
area of the sheet. The expanded metal is widely used for
reinforcing concrete in foundations, roads, floors, bridges,
etc. It is also used as lathing material.
Corrugated sheets
These are formed by passing steel sheets through grooves. These
grooves bend and press steel sheets and corrugations are formed
on the sheets. These corrugated sheets are galvanized and they
are referred to as the Galvanized Iron sheets or G.I. sheets. These
sheets are widely used for roof covering.

Plates
Steel Plates are available in different sizes and thickness varying from 5 mm to 50 mm, and weight
2
per unit area of mm are 392 N to 3925 N respectively. Steel plates are used to connect steel beams
for extension of the length. It is also used for the construction of steel built up sections.
Flat bars
Flat bars available in widths varying from 3 to 40 mm. It is used for the construction of steel grill
work, window, gates etc.
Square bars
These are bars with square sections are available in sizes varying from 5 mm
square to 25 mm square and weight per meter length are 2N and 49 N. These
are used for the construction of steel grill work, window and gates etc.

CODES FOR STEEL

IS 800: 2007 - Code of practice for general construction in steel.
IS 875: 1987 - Code of practice for design loads for buildings and structures.
(Part 1 - Dead loads, Part 2 - Imposed loads, Part 3 - Wind loads, Part 4 -
Snow loads and Part 5 - Special loads and load combinations)
IS 1893 (Part 1): 2002 - Criteria for earthquake-resistant design of structures
IS 808: 1989 - Dimensions for hot-rolled steel beams, columns, channels and angle
sections.

MISCELLANEOUS MATERIALS
GLASS
Glass is a hard, brittle, amorphous, transparent in-organic material, which is made from the pure iron
fine quartz sand or crushed quartzite rock. Nowadays, glass can be produced based on the
requirements. It is practically possible to form the lightest material.
PROPERTIES OF GLASS
The various properties of glass depends on, Dimension and shape of the glass, State of surface,
Thermal treatment conditions and Composition of glass etc.
Based on the factors described, following are the important properties of glass.
1. Glass is a hard brittle and transparent material.
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2. It can absorb, refract and transmit the light.
3. It cannot be affected by air and water
4. It cannot be affected by ordinary chemicals.
5. It appearance is good.
6. Glass is a good electrical and sound insulator at normal temperature.
7. It is available in all required colours.
8. It becomes soft and soft with the rise in temperature.
9. It can take high polish.
10. It can be washed and well cleaned.
11. Melting point varies about 1500° C
12. It has high co-efficient of expansion.
13. It has no thermal conductivity.
14. It has no crystalline structure.
15. It is affected by alkalies.
16. It is possible to weld the pieces of glass by fusion.
17. It is possible to produce the glass with any desired strength and density.
18. It is also possible to prepare the unbreakable glass.
19. It can be made bullet proof, ice proof and splinter proof. '
20. It is a highly workable material.
TYPES OF GLASS
Glasses are classified based on the properties and uses and are as follows.
(1) Soda-Lime Glass (Commercial Glass)
It is the mixture of sodium silicate and calcium silicate and it is the cheapest quality of glass. It is also
called soft glass or crown glass.
It is available in clean and clear state and it is a cheaper material. It is possible to blow (or to weld)
articles made from this glass. It is easily fusible at low temperatures
Soda-Lime glasses are used in the manufacture of, Plate glass, Window glass, Glass tubes, Laboratory
accessories (bottles, containers etc).
(2) Potash-Lime Glass
It is the mixture of silicates of potassium and calcium. It is also called Hard Glass.
It fuses at very-high temperatures. It cannot be easily melted and affected easily by solvents.
These glasses are used in the places where to with stand high temperatures (such as Combustion
Tubes, chemistry lab equipments exposed to high temperature etc.) in. Potash-Lead Glass
It is the mixture of potassium silicate and lead silicate. It is also called Flint Glass.
Its specific gravity is about 3 to 3.3 and is easily affected by aqueous solutions. It fuses very easily. It
possesses bright lustre and great refractive power. It gets easily affected by sudden temperatures. It
turns black and opaque when the furnace gases contact.
Potash-Lead glasses are used in the manufacture of, Lenses for various optical instruments,
Artificial Gems, Electric Bulbs and Prisms etc.
(3) Boro-Silicate Glass
Thermal resistance of glass can be increased by replacing the basic oxides by boron-oxides the
temperature required to melt and fuse such glass is very high. These glasses are used in the
ovenware, cooking utensils and laboratory wares etc.
It has high softening point and it can withstand sudden temperature attacks. It also has high chemical
resistance (due to the low alkali content).
Boro-Silicate glasses are used in, Laboratory apparatus in Chemical Industry, Pharmaceutical
containers, Fibre glass reinforced polymers, Textile industries and Protective helmets, boats, boat,
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piping, car chassis, ropes car exhausts etc.
(4) Common Glass
Common glasses are bottle glasses and it is the mixture of sodium silicate, calcium silicate and iron
silicate. Common (bottle) glasses are used in the manufacture of medicine bottles. It is Brown, Green
and Yellow in colour. It is easily affected by acids and it fuses with difficulty.
USES OF GLASS
Following are the important uses of glass, based on the recent development in the glass industry.
• The fibre glass reinforced with plastics can be used in the construction of furniture, cars,
trucks, lamp shades, bathroom fittings etc.
• Glass is used to form a riffle barrel which is lighter and stronger than the conventional type.
• The body of the guided missiles contains no. of glass materials.
• Optical glasses are used in the development of astronomical and bacteriological sciences.
2
• The strength of the ordinary glasses varies about 50 N/mm and the maximum strength
2
value of 420 N/mm may be manufactured with the help of modem techniques.
• Nowadays, it is possible to prepare colour glasses, which are used as windows. That glass can
be used as a transparent material in day time and sources of light at nights.
• Hollow glass walls and ceilings are used in advanced homes in order to control the sound
and heat and to permit the sunlight.
• Glass linings are applied on equipment’s to prevent the corrosion.
• Advanced deep-diving vehicles are made by strong gas material.
• A modern Boeing 707 Jet plane contains more than 5000 components of glass.

PLASTIC
The plastic is an organic material, which consists of natural or synthetic binders or resins with or
without moulding compounds. In general, it may be stated that the plastics are compounds of carbon
with other elements such as hydrogen, nitrogen and oxygen.
These are capable of flow when necessary heat and pressure are applied at some stage of their
manufacture.
CLASSIFICATION OF PLASTICS
The classification of plastics can be made by considering various aspects and for the purpose of
discussion, they can be classified according to their:
1. Physical and mechanical properties:
2. Behaviour with respect to heating
3. Structure
Physical and mechanical properties
According to this classification, the plastics are divided into four groups:
(i) Rigid plastics: These plastics have a high modulus of elasticity and they retain their shape under
exterior stresses applied at normal or moderately increased temperatures.
(ii) Semi-rigid plastics: These plastics have a medium modulus of elasticity and the
elongation under pressure completely disappears, when pressure is removed.
(iii) Soft plastics: These plastics have a low modulus of elasticity and the elongation under pressure
disappears slowly, when pressure is removed.
(iv) Elastomers: These plastics are soft and elastic materials with a low modulus of elasticity-. They
deform considerably under load at room temperature and return to their original shape,
when the load is released. The extensions can range upto ten times their original dimensions.

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Behaviour with respect to heating to
(i) Thermo-plastic (Heat non-convertible plastic)
The thermo-plastic is the general term applied to the plastics which become soft when heated and
hard when cooled. The process of softening and hardening may be repeated for an indefinite time,
provided the temperature during heat is not so high as to cause chemical decomposition. It is thus
possible to shape and reshape these plastics by means of heat and pressure. One important
advantage of this variety of plastics is that the scrap obtained from old and worn-out articles can be
effectively used again.
(ii) Thermo-setting
The thermo-setting or heat convertible group is the general term applied to the plastics which
become rigid when moulded at suitable pressure and temperature. This type of plastic passes
originally through thermo-plastic stage. When they are heated in temperature range of 127°C to
177°C, they set permanently and further application of heat does not alter their form or soften them.
The thermo-setting plastics are soluble in alcohol and certain organic solvents, when they are in
thermo-plastic stage. This property is utilized for making paints and varnishes from these plastics. The
thermo-setting plastics are durable, strong and hard. They are available in a variety of colours. They
are mainly used in engineering application of plastics.
Structure
According to this classification, the plastics are divided into two groups:
(i) Homogeneous plastic: This variety of plastic contains carbon chain i.e. the plastics of this
group are composed only of carbon atoms and they exhibit homogeneous structure.
(ii) Heterogeneous plastic: This variety of plastic is composed of the chain containing carbon and
oxygen, the nitrogen and other elements and they exhibit heterogeneous structure.
Resins
As plastics are classified into two groups, according to their behaviour with respect to heating, the
resins or binders are also broadly divided into the following two groups,
1. Thermo-plastic resins
2. Thermo-setting resins.
PROPERTIES OF PLASTICS
Following are the properties of plastics:
1) Appearance: Some plastics are completely transparent in appearance. With the addition of
suitable pigments, the plastics can be made to have appearance of variety of attractive, opaque,
stable and translucent colours.
2) Chemical resistance: The plastics offer great resistance to moisture, chemicals and solvents. The
degree of chemical resistance depends on the chemical composition of plastics. Many plastics are
found to possess excellent corrosion resistance. Hence they are used to convey chemicals.
3) Dimensional stability: This property of plastic favours quite satisfactorily with that of other
common engineering materials.
4) Ductility: The plastic lacks ductility. Hence its members may fail without warning.
5) Durability: The plastics are quite durable, if they possess sufficient surface hardness.
6) Electric insulation: The plastics possess excellent electric insulating property.
7) Finishing: Any surface treatment may be given to the plastics. It is also easy to have technical
control during its manufacture.
8) Fire-resistance: The plastics are organic in nature and hence all plastics are combustible.
9) Fixing: The plastics can be easily fixed in position. They can be bolted, clamped, drilled, glued,
screw-threaded or simply push-fitted in position.
10) Maintenance: It is easy to maintain plastic surfaces. They do not require any protective coat of
paints.

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11) Melting point: Most of the plastics have low melting point and the melting point of some plastics
is only about 50°C.
12) Recycling: The plastics used for soft-drink bottles, milk and juice bottles, bread bags, syrup
bottles, coffee cups, plastic utensils, etc. can be conveniently recycled into carpets,
detergent bottles, drainage pipes, fencing, handrails, grocery bags, car battery cases, pencil
holders, benches, picnic tables, roadside posts, etc.
13) Sound absorption: The acoustical boards are prepared by impregnating fibre-glass with
phenolic resins. This material has absorption coefficient of about 0.67.
14) Strength: The plastics are reasonably strong. The strength of plastics may be increased by
reinforcing with various fibrous materials.
15) Thermal property: The thermal conductivity of plastics is low and it can be compared with that of
wood. The foamed or expanded plastics are among the leading thermal insulators.
16) Weather resistance: The important group of plastics which can resist weather effects is one
prepared from phenolic resins. The certain plastics are seriously affected by ultraviolet light in the
presence of sunlight.
17) Weight: The plastics, whether thermo-plastic or thermo-setting, have low specific gravity, the
average being 1.30 to 1.40. The light weight of plastics reduces the transport costs and facilitates
fixing.
USES OF PLASTICS
The typical uses of plastics in building are summarized as follows:
 Bath and sink units,
 Cistern ball floats,
 Corrugated and plain sheets,
  Decorative laminates and mouldings,
 Electrical conduits,
 Electrical insulators,
 Floor tiles,
  Foams for thermal insulation,
 Jointless flooring,
 Lighting fixtures,
 Overhead water tanks,
  Paints and varnishes,
 Pipes to carry cold water,
 Roof lights, films for water-proofing,
 Safety glass, damp-proofing and concrete curing,
 Wall tiles,
  Water-resistant adhesives, etc.
 Sanitary fittings like taps, showers, basins, float balls, flushing cisterns, gratings, etc
 These products are economical, resistant to corrosion, easy in installation and light in weight.
ASBESTOS CEMENT SHEET
The asbestos is a naturally occurring fibrous mineral substance, composed of hydrous silicates of
calcium and magnesium (CaSi03, 3MgSi03). It also contains small amounts of iron oxide and alumina.
The natural asbestos can be divided into two groups, namely,
• Acid-resistant asbestos
 actinolite asbestos,
 amosite asbestos,
 anthophyllite asbestos,
 crocidolite asbestos
 tremolite asbestos S
• Non-acid-resistant asbestos.
 chrysolite asbestos
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PROPERTIES OF ASBESTOS
Following are the properties of asbestos.
• The holes can be drilled and screws can be fitted on its surface.
• It can be cut into pieces.
• It is an electrical and heat insulator.
• It is fire-proof and acid-proof.
• It is flexible, soft and non-porous.
• It is smooth like glass and silk.
• Its colour is brown, grey or white.
• Its melting point is 1200°C to 1550°C.
• Its specific gravity is 3.10.
• Its molecules are strongly bound together only in one direction and due to this, it possesses
very high tensile strength along the fibres.
• Its quality is critically affected by the length of fibres and hence this characteristic of asbestos
serves as a basis for classifying asbestos into different grades.
• It possesses a good adsorption capacity. When it is mixed with cement and cured with water,
it adsorbs i.e. retains firmly on its surface. (Thus the asbestos cement items can be
considered as reinforced cement stones with reinforcement in the form of asbestos fibres.)
USES OF ASBESTOS
The uses of asbestos are as follows.
• It is used as the covering material for magnetic coils.
• It is used as the lining material for fuse box and switch box.
• It is used for insulating boilers, furnaces, etc.
• It is used for preparing fire-proof clothes, ropes, etc.
• The asbestos felt can be prepared by coating asbestos fibres with bitumen and it is used as
damp-proof layer.
• It is used to produce the asbestos paint.
• In general, it can be stated that the uses of asbestos are daily growing - roofing, home
appliances, pipes; textiles and packing, clutch facings, brake linings, gaskets, etc.
• The asbestos cement products are prepared by mixing asbestos fibres with cement. They
include sheets and pipes. The sheets are used as roofing material and the pipes are used to
convey rainwater, seepage water, etc.

BITUMEN
Bitumen is oil based, high viscous, semi-solid material produced by removing the lighter materials (such as
liquid petroleum gas, petrol and diesel) from heavy crude oil during the refining process. Bitumen is a non-
crystalline solid or viscous material derived from petroleum, by natural or refinery process and
substantially soluble in carbon disulphide. It is asphalt in solid state and mineral tar in semi fluid state.

Bitumen is brown or black in colour. Bitumen and bituminous materials are being extensively used in
damp proofing the basements, floors, roofs, damp proof courses, painting timber and steel structural
elements; as adhesives and caulking compounds, and tars are used as binders in road works. When
combined with aggregate these are also used to provide floor surfaces. Bitumen are now more
commonly used for building purposes than is tar.
DESIRABLE PROPERTIES OF BITUMINOUS MATERIALS
For satisfactory performance as a road binder, bitumen should have following desirable properties
1. Low temperature susceptibility
2. Adequate affinity to the aggregates
3. Adequate fluidity to coat evenly the aggregates by forming thin film during mixing.
4. Adequate amount of volatiles to ensure durability.
5. Ductile and brittle

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6. Ease of mixing without and fire hazards during heating
7. No stripping when exposed to water
TYPES OF BITUMINOUS MATERIALS
Bituminous materials are classified as,
1. Bitumen
(a) Cutback bitumen
(b) Bitumen emulsion
(c) Rubber bitumen
3. Tar
4. Tar-bitumen
In general, bituminous material used for construction is classified into bitumen tar and tar-bitumen
mix.
1. Cutback bitumen
The Cutback bitumen is a liquid binder. It is obtained by dissolving a bitumen material with suitable
volatile solvent. The solvent used for dissolving the bitumen, not only serves as a substitute for heat,
but also helps in increasing the liquefying effect over a long period of time. The cut back bitumen is
suitable for direct application in road construction. In addition to that, it is used on the surface of soil
aggregate road, in warm climates to prevent dust nuisance.
2. Bitumen emulsion
An emulsion is a mixture of two immiscible liquids. The mixing is done in the presence of an
emulsifying agent such as resin or soap, which help in mixing the two liquids. Generally bitumen
emulsions are of two types.
In first type, minute globules of bitumen are dispersed in water. In second type consist of bitumen
water mixture, in which upto about 10% water forms the dispersed phase and the cutback bitumen is
the continuous phase. This second type if also called as inverted emulsion.
3. Rubber bitumen
It contains a mixture of bitumen and rubber latex of different forms. They get more cohesion and
stability. They are most resilient than one without. They also serve as better cushion to vibrations and
traffic shocks. The addition of rubber also increases the softening point and viscosity of the
bituminous mixture.
Rubber bitumen is less temperature susceptible. In cold areas, the addition of 5.5 to 7% rubber by
weight of bitumen reduces the surface cracking.
4. Road tar
It is a viscous liquid, black in colour with adhesive properties, obtained by destructive distillation of
organic matters such as wood, coal, shale, etc. In the destructive distillation process, the material is
subjected to heat alone, in the absence of air.
The first step for the production of tar is the carbonization of coal to produce crude tar. In the second
stage crude tar is refined by distillation process. The different grades of road tar along with their uses
are tabulated below.
S.No. Grade Uses
1. RT-1 Surface painting under exceptionally cold weather
2. RT-2 Surface painting under tropical climatic conditions
3. RT-3 Surface paintings, renewal coats and pre mixing chips.
4. RT-4 Pre mixing tar macadam in base course.
5. RT-5 Grounding.

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PROPERTIES
Following are the properties of Bitumen
1. Adhesion
2. Resistance to Water
3. Hardness
4. Viscosity and Flow
5. Softening Point
6. Ductility
7. Specific Gravity
8. Durability
9. Versatility
10. Economical
11. Strength
Adhesion:
The adhesive property of bitumen binds together all the components without bringing about any
positive or negative changes in their properties. Bitumen has the ability to adhere to a solid surface in
a fluid state depending on the nature of the surface. The presence of water on the surface will
prevent adhesion.
Resistance to Water:
Bitumen is insoluble in water and can serve as an effective sealant Bitumen is water resistant.
Hardness:
To measure the hardness of bitumen, the penetration test is conducted, which measures the depth
of penetration in tenths of mm. of a weighted needle in bitumen after a given time, at a known
temperature.
Viscosity and Flow:
The viscous or flow properties of bitumen are of importance both at high temperature during
processing and application and at low temperature to which bitumen is subjected during service.
Softening Point
This property make us to know whether given bitumen can be used at the particular place i.e.
softening point value should be higher than pavement temperature otherwise bitumen present in the
layer get soften and come out.
Ductility:
Ductility test is conducted to determine the amount bitumen will stretch at temperature below its
softening point.
Specific Gravity:
Specific gravity of a binder does not influence its behaviour. But all the same, its value is needed in
mix design. The property is determined at 27° C.
Durability:
Bitumen durability refers to the long-term resistance to oxidative hardening of the Material in the field.
Versatility:
Due to versatility property of Bitumen it is relatively easy to use it in many applications because of its
thermoplastic property. It can be spread easily along the underlying pavement layers as it liquefies
when heated making the job easier and hardens in a solid mass when cooled.
Economical:
It is available in cheaper rates almost all over the world which makes it feasible and affordable in
many applications.
Strength:
Though the coarse aggregates are the main load bearing component in a pavement, bitumen or
asphalt also play a vital role in distributing the traffic loads to the layers beneath.

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APPLICATION OF BITUMEN AND BITUMINOUS MATERIAL
Various applications of bituminous materials are studied under the following topics.
1. Bitumen and tar binders are used for making asphalt concretes. Asphalt Concretes are used for
manufacturing,
a. Roof water-proofing
b. Steam proofing materials and items
c. Roof-waterproofing pastes
d. Roof coverings and waterproofing
e. Road construction mastics and emulsions.
2. Bitumen Emulsions (Bitumen content 5%, Emulsifier content 0.01 % to 5%)
Bitumen Emulsions are used for making water and steam-proof coatings, priming surfaces in
preparation for waterproofing gluing piece and coil materials and making the surfaces of items
hydrophobic. Bitumen pastes are prepared from bitumen, water and emulsifiers.
3. Mastics
Mastics are used for roofing and waterproofing. Bituminous wall and sheet materials for roofing and
waterproofing are widely employed in building practice.
4. Impregnated Rolled Materials
Impregnated rolled materials are sub classified based on the type of binder into bitumen, tar, tar
bitumen, petroleum asphalt and bitumen-polymer varieties. By structure, impregnated roll materials
are subdivided into coated and non-coated types. Coated impregnated cardboard roll materials
include roofing felt, tar paper, tar-bitumen and petroleum asphalt materials.
5. Roofing Felt
Roofing felt is a roll material prepared by impregnating roof cardboard with soft bitumen,
subsequently coating it on one or both sides with high-melting bitumen and finally facing it with
finally-ground mineral powder, mica or coloured mineral granules.
6. Asphalt Reinforced Mats
Asphalt reinforced mats are prepared by coating impregnated fiberglass cloth on both the sides with
bitumen or waterproofing asphalt mastic. By the impregnating material and composition of the
covering layer-asphalt reinforced mats are subdivided into common and high heat-resistant grades.
7. Water Proofing Asphalt Slabs
Water Proofing Asphalt slabs are manufactured by covering pre-impregnated fiberglass or metal mesh.

Slabs are made of either reinforced or plain slabs. Non-reinforced (Plain) slabs are made 0.8 m to lm
long, 0.5 to 0.6 m wide and 10 to 20 mm thick. Reinforced slabs are lm to 1.2 m in length long, 0.75 to
1.2 m wide and 20 to 40 mm in thick. These are used for glued-on waterproofing work and filling of
deformation joint, during the cold season.
8. Water Proofing Stones
Water proofing Stones are manufactured by impregnating artificial or natural porous materials (Brick,
Concrete, Tuff, chalk, limestone etc.) with bitumen or coal tar products to a depth of 10mm to 15mm.
They are employed for making waterproof brickwork and lining with the use of cement and asphalt
mortars.
9. Prefabricated Water Proofing Reinforced Concrete Elements
Prefabricated Water proofing reinforced concrete elements are manufactured by impregnating pre-
fabricated reinforced concrete elements (piles, slabs, sections of pipes, tubing etc.) with organic
binders to a depth of 10 to 15mm. These items are used for Anti-Corrosion Water- Proofing of
installations exposed to simultaneous action of impact loads and mineralized water.

ADHESIVES
An adhesive is a substance which is used to join two or more parts so as to form a single unit. The
quality of an adhesive is based on its degree or intensity of sticking, its durability, its heat resistance,

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the strength of bond developed after drying or setting and the time required to develop the required
bond, etc. The glue is a general term which is used to indicate an adhesive substance.
THE ADVANTAGES AND THE DISADVANTAGES OF ADHESIVES
The application of adhesive has the following advantages over the conventional methods of bolting,
riveting and welding:
 A wide variety of combinations in joining is possible.
 It can be used for bonding the surfaces of glass, metal, plastics and wood.
 It creates a massive effect.
 It is possible to prevent corrosion between different metals joined by adhesive.
  It produces adequate strength.
 The permeable joint can be made impermeable for water and gas by the application of adhesives.
 The process of applying adhesive is easy, economical and speedy.
The disadvantages of adhesives are as follows:
 It is not possible to adopt any adhesive for all substances. Depending upon the properties of
 substances to be joined, suitable adhesive has to be selected.
 The adhesive substance does not become strong immediately after its application. It requires
 some time to attain the desired strength.
 The adhesive substance generally does not remain stable at high temperature.
PROPERTIES OF ADHESIVES
Selecting a structural strength adhesive for a specific application requires performance criteria of
several characteristics.
Bond Making Properties
 Degree of surface preparation necessary
  Time to handling strength
 Cure conditions of heat or room temperature, the degree of pressure, and the fixturing to
 maintain that pressure
 Viscosity for pumping and staying in place after application. Pseudoplastic and thixotropic
qualities are desireable so that the adhesive thins during the shearing action of delivery and
 thickens in place without further shearing.
 Application with automated bulk systems or hand-held applicator to meet varying production
requirements.
Cured Bond Properties:
Physical Properties
 Adhesion to a variety of substrates allows bonding of dissimilar materials if necessary
 High cohesive strength is desirable
  Flexibility improves peel strength by flexing with peel stress
 High elastic modulus of substrate and adhesive resists stress at the bond line

 High damping capacity of the adhesive dissipates dynamic stresses of vibration, motion, &
 impact throughout the bond & peel stresses at the bond line
 Flexibility and damping resistance resists thermal expansion stresses when the coefficients of
thermal expansion are different between adhesive and substrates
Environmental Resistance
 Resists end-use or post-processing temperatures to maintain adhesive chemistry and the
 physical bond
  Withstands physical shock at a range of temperatures
 Maintains adhesive performance despite exposure to UV light, rain, salt water, and other
weathering conditions

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Chemical Resistance
 Ability to withstand degradation from diesel fuel, solvents and other chemicals
TYPES OF ADHESIVES AND USES
Following are the various types of adhesives
(1) Albumin Glues: It is a glue of better quality. It is not attacked by water. It is used for making
furniture.
(2) Animal Protein Glues: It is obtained by boiling waste pieces of skins, bones, etc. of animals with
hot water. The animal glue develops strong and tough joints and it is easy to apply. But it is
affected by damp and moist conditions. It is available in the form of cakes, flakes, granules,
jelly, pearls and sheets. It is used in the manufacture of plywood, laminated timbers, etc.
(3) Glues from Natural Resins: It is prepared from natural resins. It is used for labelling building
paper, etc.
(4) Glues from synthetic Resins: These glues are based on synthetic resins. They may either be
thermo-setting glues or thermo-plastic glues. The thermo-setting glues become permanent,
once they are set. The thermo-plastic glues can be made plastic again by reheating. All
synthetic glues are fire-proof, strong and water-proof. The setting time of synthetic glues can
be regulated by varying the type or kind and quality of the hardener. They resist the attack by
fungi and they possess non-staining qualities.
The synthetic resins are mainly of four types:
 Melamine resins: They require heat and pressure for setting. They are used in the
manufacture of plywood.

 Phenolic resins: They are available either in liquid, film or powder form. They require
heat and pressure to form a permanent strong bond. They are used in the manufacture
of resin-bonded plywood.

 Resorcinol resins: They are in the form of dark viscous liquids. They are resistant to bacteria,
fungi, heat and moisture. They become hard in short time at low temperatures.

 Urea resins: They are available in the form of syrups and powders. They are extensively
used in joinery work to form water-resistant glue joints.

(5) Nitrocellulose glues: It is prepared from pyroxilin which is a nitrated cellulose. It is derived by
treating cellulose with nitric acid. It produces films which strongly adhere to the glass.
(6) Rubber glues: It is prepared by dissolving rubber in benzene. It is used for joining rubber,
plastics, glass, etc.
(7) Special glues: These are specially prepared to join metals. The cycleweld is a modified form of
rubber and it is used to join aluminium sheets. The araldite is another variety of special glue. It
is used to join the light metals.
(8) Starch glues: It is prepared from vegetable starch. It has good strength in dry condition. But it is
not moisture resistant. It is cheap and is used for inferior quality of plywood.
(9) Vegetable glues: It is prepared from natural gums and starches. It is used for preparing paper
board articles, labelling, etc.

ALUMINIUM
Aluminium (or aluminum) is a silvery white, soft, ductile metal and it is the third most abundant
metal in the Earth's crust. It has low density and high ability to resist corrosion. Structural
components made from aluminium and its alloys are very important to the Aerospace industry and
are important in other areas of transportation and structural materials. The most useful compounds
of aluminium, at least on a weight basis, are the oxides and sulphates.

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PROPERTIES OF ALUMINIUM.
Following are the important properties of aluminium.
2. Aluminium is a relatively soft, durable, light weight, ductile and malleable metal.
3. It is silvery to dull gray colour, depending on the surface roughness.
4. It is non-magnetic and does not easily ignite.
5. A fresh film of aluminium serves as a good reflector (approximately 92%) of visible light and an
excellent reflector (as much as 98%) of medium and far infrared radiation.
6. The yield strength of pure aluminium is 7 to 11 MPa, while aluminium alloys have yield
strengths ranging from 200 MPa to .600 MPa.
7. Aluminium has about one-third the density and stiffness of steel. It is easily machined and can
be easily extruded.
8. Aluminium is a good thermal and electrical conductor (Having 59% the conductivity of copper,
both thermal and electrical, while having only 30% of copper’s density)
9. Aluminium is capable of being a super conductor, with a superconducting critical temperature
of 1.2 Kelvin
10. Aluminium has high corrosive resistance (This is due to a thin surface layer of aluminium oxide
that forms when the metal is exposed to air, effectively preventing further oxidation.)
11. The specific gravity of aluminium is about 2.70.
12. Aluminium can be riveted and welded, but cannot be soldered.
13. It can be tempered at 350° C.
14. The melting point is 657° C.
15. Tensile strength is 117.2 N/mm2 in the cast form and 241.3 N/mm2 when drawn into wires.
ADVANTAGES OF ALUMINIUM WITH OTHER BUILDING MATERIALS
Aluminium is a costlier material than the other, however its durability and other properties makes
aluminium as an important building material due to the following advantages.
Asbestos Cement Sheets:

 Asbestos Cement Sheet is 7 times heavier than the aluminium sheets and hence, it needs
 heavier support to withstand the load from sheets.
 Aluminium is stronger than the Asbestos Cement Sheet.
Corrugated Galvanized Iron Sheets:
 Corrugated galvanized iron sheets are costlier than the aluminium sheets.
 Aluminium sheets require light structural supports
Steel:
 Steel can be adopted in standard sizes and shapes (like I, T and Channel section) and
 aluminium offers the structures of different shapes and profiles.
 The designing of aluminium structures are easier than the designing of steel structures.
 Continuous length of aluminium sections can be achieved by extrusion of aluminium.
Timber:
 The initial cost of timber is high and the maintenance cost is also high for timber than
 aluminium.
 The replacement of timber by aluminium is also of vital importance from the point of
preserving the forest.
GENERAL USE
Aluminium is the most widely used non-ferrous metal. Global production, of aluminium in 2005 was
32 million tones. Aluminium can be alloyed, which improves its mechanical properties, especially
when tempered.

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Module I Dept. of Civil Engineering, MEAEC
Some of the uses for aluminium metal are in transportation (automobiles, aircraft, trucks, railway
cars, marine vessels, bicycles, etc.) as sheet, tube, castings, etc.
 Construction (windows, doors, siding, building wire, etc.)
 Street lighting poles, sailing ship masts, walking poles, etc.
  Electrical transmission lines for power distribution
 Super Purity Aluminium (SPA, 99.980% to 99.99% Al), used in electronics and CDs.
 Heat sinks for electronic appliances such as transistors and CPUs.
  Substrate material of metal-core copper clad laminates used in high brightness LED lighting.
 Powdered aluminium is used in paint, and in pyrotechnics such as solid rocket fuels and
 termite.
 Aluminium can be reacted with hydrochloric acid or with sodium hydroxide to produce
 hydrogen gas.
 Aluminium or Aluminium-Copper Alloy is used to make coins.
  A wide range of household items, from cooking utensils to baseball bats, watches.
 Aluminium is usually alloyed. (A thin layer of aluminium can be deposited onto a flat surface
by Physical Vapour Deposition or Chemical Vapour Deposition or other chemical means to
form optical coatings and mirrors) It is used as pure metal only when corrosion resistance and
workability is more important than strength or hardness.

*******************************
Prepared By

NAJEEB. M
Assistant Professor
Dept. of Civil Engineering
MEA Engineering College

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MODULE 2
Civil Engineering, MEAEC Module II

MODULE 2
Syllabus:
Concrete – Aggregates – Mechanical & Physical properties and tests – Grading requirements –
Water quality for concrete –
Admixtures – types and uses – plasticizers – accelerators – retarders –water reducing agents
Making of concrete - batching – mixing – types of mixers – transportation – placing – compacting –
curing
Properties of concrete – fresh concrete – workability – segregation and bleeding - factors affecting
Workability & strength – tests on workability – tests for strength of concrete in compression, tension
& flexure
Concrete quality control – statistical analysis of results – standard deviation –acceptance criteria –
mix proportioning (B.I.S method) – nominal mixes.

INTRODUCTION
Concrete is the most commonly used manmade construction material. It has become very popular
not only among civil engineers but among common people also.

Production of concrete

The production of concrete involves two distinct but equally important activities. One is related to
materials required for concrete and the other to processes involved in its production.

Material

The activity related to materials involves their

(1) Selection and
(2) Proportioning

Process
The activity related to process involved in Production of concrete involves,
(1) Mixing
(2) Transportation
(3) Placement
(4) Compaction and
(5) Curing

Out of above activities, more often than not, it is the process' which is responsible for quality of the
concrete, though the cost of the concrete is mainly governed by the cost of the materials. The
selection of materials and their proportioning is usually well taken care of at higher levels but the
process is left to the lower levels. The expenditure incurred on materials goes waste if the process is
not taken care of. Ignorance and lack of appreciation of good practices are the main reasons for the
poor quality of concrete. Therefore, if we are able to control the process, we can obtain far better
quality of concrete at no extra expenditure.

Ingredients of concrete

The basic ingredients of concrete are as given below

(1) Cement - It is the most important and costliest ingredient of concrete. The mix-design of concrete
indirectly means optimizing the use of cement for obtaining the desired properties of concrete in
green as well as hardened state. It affects the overall economy of the structure too.

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Module II Dept. of Civil Engineering, MEAEC
Different types of cements are available for different type of structures and different types of
locations. Judicious selection of cement is necessary for the longevity of the structure.
(2) Aggregate - The aggregates give volume to the concrete because these occupy maximum space in
the total volume of concrete. Efforts should be made to use maximum quantity of aggregates as
these increase the volumetric stability of concrete and make the mix-design more economical.
(3) Water - It is indispensable because it is required for reaction of hydration. But its use should be
restricted to minimum as possible considering the requirement for chemical reaction with
cement and workability only. Any excess water is destined for evaporation, leaving capillary-
pores in the concrete. Eventually, strength and durability both will be adversely affected when
water is excessive.
(4) Admixture - It is an optional ingredient which is used only for some specific purpose. It is used to
modify some of the properties of concrete like setting time, workability or surface finishing
characteristics etc. But admixture should not be used to compensate for bad quality of concrete
instead it should be used as a supplement to good construction practices. Though the newer
versions of concrete i.e. HPC, RMC and SCC, the use of admixtures has become indispensable.

AGGREGATE
Aggregates give body to the concrete. They also reduce shrinkage and effect overall economy. Since
aggregate is cheaper than cement, it is economical to put as much aggregates as practically possible. Not
only the use of more volume of aggregate in concrete is economical, it also provides higher volume
stability to the concrete. Generally they occupy 60-70% of the total volume of concrete. At the same time
the aggregates should be strong because the weak aggregates can't make strong concrete and they may
limit the strength of concrete. Therefore the selection of aggregate becomes very vital.

Earlier aggregates were viewed as an inert ingredient of concrete but now their importance has been
understood and these are no more considered inert. Their physical, chemical as well as thermal
properties greatly influence the properties of concrete.

TYPES OF AGGREGATES
Classification based on size
In terms of size, there are two broad categories of aggregate as given below:

1. Coarse Aggregate
  The aggregates which is retained on IS 4.75mm sieve
  Further divided into
(a) Graded Aggregates : Coarse aggregates which contain particles of all sizes from
4.75mm to 75mm. The aggregates whose particles are so proportioned as to give
a definite grading, is called a well graded aggregate
(b) Single sized aggregates: Course aggregates which contain particles f single sieve size.

2. Fine Aggregates
  Aggregates passing through IS 4.75mm sieve
  Further divided into
(a) Natural Sand : Fine aggregates formed by natural disintegration of rocks
(b) Crushed Stone sand : Fine aggregates made by crushing natural gravels
(c) Broken fine aggregates : Obtained by crushing broken brick (Surkhi)

3. All in aggregates
 Aggregates which contain both course and fine aggregates

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 Dept. of Civil Engineering, MEAEC Module II
Classification based on source
1. Natural Aggregates
 Aggregates obtained from rocks by quarrying, crushing and then screening.

 Most igneous rocks make highly satisfactory concrete aggregates because they are normally
hard, tough and dense.

 The quality of aggregates derived from sedimentary rocks vary in quality depending upon
the cementing material and the pressure under which these rocks are originally compacted

 Many metamorphic rocks particularly quartzite and gneiss have been used for production of
good concrete aggregates.

2. Artificial aggregates
 Brick bats, blast furnace slag and synthetic aggregates are artificial aggregates

 Good quality brick bats, free from dust and lime mortar may be used for mass
concrete works But not suitable for RCC works

 Good quality blast furnace slag may be used as aggregates to produce concrete. It has
 good fire resistant quality
3. Recycled aggregates
 The ruble of demolished buildings, made free from undesirable constituents, crushed to
 aggregate size and graded may be used for concrete.
 Strength is not good

Classification based on aggregate shape

1. Rounded Aggregates
  River sand, seashore sand, wind-blown sand and river gravels are of rounded shape
  Need less cement paste to make concrete
  Interlocking between particles is poor
 Not suitable for high strength concrete

2. Irregular Aggregates
 Partly shaped aggregates are called irregular aggregates

3. Angular Aggregates
  These aggregates have sharp edges and rough surfaces.
  All types of crushed rocks are good examples for this type of aggregates
  They need more cement paste, since voids are more in the aggregates
  Bond developed between aggregates is good
 Ideal for producing high strength concrete

4. Flaky Aggregates
 Flaky aggregates have thickness less than 0.6 times mean sieve size to which particles
 belong.
  Flaky aggregates reduce the durability of concrete
 Flaky aggregates should not be more than 15% for any concrete work

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Module II Dept. of Civil Engineering, MEAEC

Shape of aggregates

According to the field experience, the rounded aggregates are preferred for the low grade of
concrete where w/c ratio is more than 0.4, but angular aggregates are preferred for higher grade of
concrete and where the requirement of flexure strength and interlocking is higher.

Angular aggregates exhibit a better interlocking effect in concrete, which makes it superior in
concrete used for roads and pavements. The total surface area of rough textured angular aggregate is
more than smooth rounded aggregate for the given volume. By having greater surface area, the
angular aggregate may show higher bond strength

Classification based on Unit weight

On the basis of unit weight aggregates are classified as normal weight, heavy weight and light weight
aggregates.

Sl Unit Wt
Aggregate 3 Examples
No. kN/m
1 Normal Weight 23–26 Gravel, Sand stone, Lime stone
2 Heavy Weight 26–29 Magnetite, barite
3 Light Weight 12–18 Dolomite, Pumice, Cinder

PROPERTIES OF AGGREGATES
The properties of aggregates can be broadly be categorized as:
1. Physical properties
i. Bulk Density
ii. Specific gravity
iii. Voids
iv. Porosity and absorption
v. Moisture Content
vi. Soundness

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 Dept. of Civil Engineering, MEAEC Module II
2. Mechanical properties
i. Texture
ii. Strength
iii. Toughness
iv. Hardness

Mechanical Properties of Aggregates

1. Surface Texture
It is the surface quality of aggregate in terms of roughness. Texture of aggregate depends upon
its hardness, grain size, pore structure and degree to which it has been polished by the external
forces like wind and water. There can be two types of texture for aggregate as given below:

(a) Smooth texture

(b) Rough texture

(a) Smooth texture

Generally hard, dense and fine grained aggregates are smooth textured. The surface area is
less due to less irregularities, therefore these require less quantity of paste for lubrication.
But as smoothness increases, the bonding area with matrix also reduces. Therefore, although
more compressive strength may be achieved due to less requirement of water, yet the
flexure strength decreases due to poor bonding and interlocking.

(b) Rough texture

Rough textured aggregates exhibit higher strength in tension as compared to smooth
aggregates, but compressive strength is less because higher w/c ratio is required for the same
workability.

2. Strength
Since concrete is an assemblage of individual pieces of aggregate bound together by cementing
material, its properties are based primarily on the quality of the cement paste. We cannot make
good strength concrete from poor quality cement paste, even if the aggregates are strong.

From the above it can be concluded that while strong aggregates cannot make strong concrete,
for making strong concrete, strong aggregates are an essential requirement. In other words, from
a weak rock or aggregate strong concrete cannot be made.

By and large naturally available mineral aggregates are strong enough for making normal strength
concrete. The test for strength of aggregate is required to be made in the following situations:

  For production of high strength and ultrahigh strength concrete.

  When contemplating to use aggregates manufactured from weathered rocks.
 Aggregate manufactured by industrial process.

Aggregate crushing value test is conducted to determine the crushing strength of coarse
aggregates

3. Toughness
Resistance to impact is called toughness. Concrete used for roads and aircraft runways should
have sufficient resistance to impact.

4. Hardness
Resistance to wear or abrasion is defined as hardness. The pavements and industrial floors should
be made with concrete having hard aggregates. Los Angles test is recommended for determining
hardness of aggregates

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Module II Dept. of Civil Engineering, MEAEC
Physical Properties of Aggregates
1. Bulk Density
The bulk density or unit weight of an aggregate gives valuable information regarding the shape
and grading of the aggregate. For a given specific gravity the angular aggregates show a lower
bulk density. The bulk density of aggregate is measured by filling a container of known volume in
a standard manner and weighing it. Bulk density shows how densely the aggregate is packed
when filled in a standard manner. The bulk density depends on the particle size distribution and
shape of the particles.

The higher the bulk density, the lower is the void content to be filled by sand and cement. The
sample which gives the minimum voids or the one which gives maximum bulk density is taken as
the right sample of aggregate for making economical mix.

2. Specific gravity
In case of aggregates the following two types of specific gravity terms are used
(a) Absolute Specific gravity: It refers to weight of the aggregates per unit volume of solid material

(b) Apparent Specific gravity: Aggregates generally contain voids. The weight of unit volume of
aggregates including voids is termed as apparent specific gravity.

Low specific gravity indicates poor durability and low strength. Lower the specific gravity of the
aggregates lower the density of concrete.

Specific gravity of aggregates is made use of in design calculations of concrete mixes. Specific
gravity of aggregate is also required in calculating the compacting factor in connection with the
workability measurements. Similarly, specific gravity of aggregate is required to be considered
when we deal with light weight and heavy weight concrete. Average specific gravity of the rocks
vary from 2.6 to 2.8.
3. Voids
The space between the particles of the aggregates is termed as voids. It is the difference between
the gross volume of aggregates and the volume of aggregates particles. Generally it is expressed
as void ratio, where
Void ratio = 1 −

Void ratio indicates the requirement of mortar to fill.

4. Water absorption
In mix-design calculations, we assume aggregate to be saturated and surface dry (SSD). Actually it
may be in a different state of dryness as given under.

(a) Bone dry (c) Saturated and surface dry (b) Air dry (d)
Moist

If aggregate is drier than SSD, it will absorb water from concrete and reduce the workability. On the
other hand if it moist, it will contribute water in the concrete reducing the strength. The different
stages can be as given in Fig.

Water Absorption

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Dept. of Civil Engineering, MEAEC Module II
5. Moisture Content
Moisture content is the water held by aggregates on its surface in excess of surface dry condition.
The water cement ratio specified in concrete mix is based on the assumption that the aggregates
are in surface dry condition. Hence, if aggregates are air dry, corrective water should be added
and in the case aggregates are in moist condition corrective water is to be deducted.
6. Soundness
Soundness refers to the ability of aggregate to resist excessive changes in volume as a result of
changes in physical conditions. These physical conditions that affect the soundness of aggregate
are the freezing the thawing, variation in temperature, alternate wetting and drying under
normal conditions and wetting and drying in salt water. Aggregates which are porous, weak and
containing any undesirable extraneous matters undergo excessive volume change when
subjected to the above conditions. Aggregates which undergo more than the specified amount of
volume change is said to be unsound aggregates.

The soundness test consists of alternative immersion of carefully graded and weighed test sample
in a solution of sodium or magnesium sulphate and oven drying it under specified conditions. The
accumulation and growth of salt crystals in the pores of the particles is thought to produce
disruptive internal forces similar to the action of freezing of water or crystallisation of salt. Loss in
weight, is measured for a specified number of cycles. As a general guide, it can be taken that the
average loss of weight after 10 cycles should not exceed 12 per cent and 18 per cent when tested
with sodium sulphate and magnesium sulphate respectively.

GRADING OF AGGREGATES

Aggregate comprises about 55 per cent of the volume of mortar and about 85 per cent volume of
mass concrete. Mortar contains aggregate of size of 4.75 mm and concrete contains aggregate up to a
maximum size of 150 mm. Thus it is not surprising that the way particles of aggregate fit together in
the mix, as influenced by the gradation, shape, and surface texture, has an important effect on the
workability and finishing characteristic of fresh concrete, consequently on the properties of hardened
concrete.

Typical packing and grading of aggregates of different sizes

One of the most important factors for producing workable concrete is good gradation of aggregates.
Good grading implies that a sample of aggregates contains all standard fractions of aggregate in
required proportion such hat the sample contains minimum voids. A sample of the well graded
aggregate containing minimum voids will require minimum paste to fill up the voids in the aggregates.
Minimum paste will mean less quantity of cement and less quantity of water, which will further mean
increased economy, higher strength, lower-shrinkage and greater durability.

SIEVE ANALYSIS OF AGGREGATES

It is a process of dividing a sample of aggregate into various fractions, each consisting of particles of
same nominal size. The resultant particle size distribution’ is called the gradation.

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Module II Dept. of Civil Engineering, MEAEC
Grading pattern of a sample of C.A. or F.A. is assessed by sieving a sample successively through all the
sieves mounted one over the other in order of size, with larger sieve on the top. The material
retained on each sieve after shaking, represents the fraction of aggregate coarser than the sieve in
question and finer than the sieve above. Sieving can be done either manually or mechanically.

Set of Sieves assembled for conducting Sieve analysis

Standard sizes of the sieve are: - 80mm, 40mm, 20mm, 10mm, 4.75mm, 2.36mm, 1.18mm, 600µ,
300µ, 150µ

The gradation of aggregate is very important not only for concrete strength but for workability also.
In fact the gradation of FA has much greater effect on concrete qualities. FA should not be very
coarse as it may cause segregation or bleeding and also result into harsh concrete. It should not be
very fine also, otherwise it will have more water demand.

The gradation of FA can be represented by a mathematical index called 'Fineness Modulus' (FM)
which determines relative fineness of material.

Mathematically,

FM = Cumulative percentage of aggregates retained on each standard sieves / 100

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Dept. of Civil Engineering, MEAEC Module II

Typical example of sieve analysis

Larger the value of FM, coarser will be the aggregate as given in Table-2 below:

Table-2
Sand FM
Fine Sand 2.2 - 2.6
Medium Sand 2.6 - 2.9
Coarse Sand 2.9 - 3.2

FM more than 3.2 is generally considered unsuitable for concrete.

As per IS: 383-1970, the gradation of FA has been done by dividing into four zones i.e. Zone-I, Zone-II,
Zone-III & Zone-IV. The grading limits are shown in Table-3.

Table-3
Percentage Passing
IS Sieve Zone-I Zone-II Zone-III Zone-IV
10 mm 100 100 100 100
4.75 mm 90-100 90-100 90-100 95-100
2.36 mm 60-95 75-100 85-100 95-100
1.18 mm 30-70 55-90 75-100 90-100
*600 µ 15-34 35-59 60-79 80-100
300 µ 5-2 8-30 12-40 15-50
150 µ 0-10 0-10 0-10 0-15

* Since the values for 600 µ size are not overlapping for different zones, it is used for confirming the
zone of a sample of FA.

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Module II Dept. of Civil Engineering, MEAEC
Zone-I represents the course and zone-IV represents the finer sand in all the four zones. Fine
aggregate belonging to Zone-IV should not be used in RCC works unless tests have been made for
suitability of mix proportion.

GAP GRADING OF AGGREGATES

This is relatively a different concept of aggregate gradation. It is different from the conventional
adopted well gradation' or continuous gradation' which means representation of all the standard
particle sizes in certain proportion. Assumption made in well gradation is that voids created by the
higher size of aggregate will be filled-up by immediate next lower size of aggregate and again some
smaller voids will be left out which will again be filled-up by next lower size aggregates.

But it is easier said than done. Practically it has been found that voids created by a particular size may be
too small to accommodate the very next lower size. Therefore the next lower size may not be
accommodated in the available gap without lifting the upper layer of the existing size. Therefore, Particle
Size Interference' is created which disturbs the very process of achieving the maximum density.

In fact the size of voids created by a particular size of aggregates can accommodate the second or
third lower size aggregates only i.e. voids created by 40 mm will be able to accommodate size equal
to 10 mm or 4.75 mm but not 20 mm. This concept is called Gap Grading'.

Advantages of Gap Grading

  Requirement of sand is reduced by 26 to 40%

 Specific area of total aggregate will be reduced due to less use of sand

 Point contact between various size fractions is maintained, thus reducing the drying shrinkage.

 It requires less cement as the net volume of voids is reduced to a greater extent.

A word of caution while using gap grading is that sometimes it may lead to segregation and may even
alter the anticipated workability. Therefore tests must be conducted before adopting this gradation.

TESTING OF AGGREGATES
Test for Determination of Flakiness Index

The flakiness index of aggregate is the percentage by weight of particles in it whose least dimension
(thickness) is less than three-fifths of their mean dimension. The test is not applicable to sizes smaller
than 6.3 mm.

This test is conducted by using a metal thickness gauge, of the description shown in Fig. below. A
sufficient quantity of aggregate is taken such that a minimum number of 200 pieces of any fraction
can be tested. Each fraction is gauged in turn for thickness on the metal gauge. The total amount
passing in the gauge is weighed to an accuracy of 0.1 per cent of the weight of the samples taken. The
flakiness index is taken as the total weight of the material passing the various thickness gauges
expressed as a percentage of the total weight of the sample taken.

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Dept. of Civil Engineering, MEAEC Module II

Thickness Gauge (IS: 2386 (Part I) – 1963)

Test for Determination of Elongation Index

The elongation index on an aggregate is the percentage by weight of particles whose greatest
dimension (length) is greater than 1.8 times their mean dimension. The elongation index is not
applicable to sizes smaller than 6.3 mm.

This test is conducted by using metal length gauge of the description shown in Fig. below. The
procedure is similar to that of finding flakiness index.

The elongation index is the total weight of the material retained on the various length gauges expressed
as a percentage of the total weight of the sample gauged. The presence of elongated particles in excess of
10 to 15 per cent is generally considered undesirable, but no recognized limits are laid down.

Length Gauge. (IS: 2386 (Part I) – 1963)

Test for Determination of Specific Gravity

Indian Standard Specification IS : 2386 (Part III) of 1963 gives various procedures to find out the
specific gravity of different sizes of aggregates. The following procedure is applicable to aggregate
size larger than 10 mm.

A sample of aggregate not less than 2 kg is taken. It is thoroughly washed to remove the finer particles and
dust adhering to the aggregate. It is then placed in a wire basket and immersed in distilled water at a
temperature between 22° to 32°C. Immediately after immersion, the entrapped air is removed from the
sample by lifting the basket containing it 25 mm above the base of the tank and allowing it to drop 25
times at the rate of about one drop per sec. During the operation, care is taken that the basket and
aggregate remain completely immersed in water. They are kept in water for a period of 24 ± 1/2 hours
afterwards. The basket and aggregate are then jolted and weighed (weight A1) in water at a

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Module II Dept. of Civil Engineering, MEAEC
temperature 22° to 32° C. The basket and the aggregate are then removed from water and allowed to
drain for a few minutes and then the aggregate is taken out from the basket and placed on dry cloth
and the surface is gently dried with the cloth. The aggregate is transferred to the second dry cloth
and further dried. The empty basket is again immersed in water, jolted 25 times and weighed in
water (weight A2). The aggregate is exposed to atmosphere away from direct sunlight for not less
than 10 minutes until it appears completely surface dry. Then the aggregate is weighed in air (weight
B). Then the aggregate is kept in the oven at a temperature of 100 to 110°C and maintained at this
temperature for 24 ± 1/2 hours. It is then cooled in the air-tight container, and weighed (weight C).
C C
Specific Gravity = ; Apparent Sp. Gravity =
B−A C−A

Specific Gravity = 100 (B−C)

C

Where, A = the weight in gm of the saturated aggregate in water (A1 – A2)

B = the weight in gm of the saturated surface-dry aggregate in air, and
C = the weight in gm of oven-dried aggregate in air.

Test for Determination of Bulk Density and Voids

Bulk density is the weight of material in a given volume. It is normally expressed in kg per litre. A
cylindrical measure preferably machined to accurate internal dimensions is used for measuring bulk
density.

The cylindrical measure is filled about 1/3 each time with thoroughly mixed aggregate and tamped
with 25 strokes by a bullet ended tamping rod, 16 mm diameter and 60 cm long. The measure is
carefully struck off level using tamping rod as a straight edge. The net weight of the aggregate in the
measure is determined and the bulk density is calculated in kg/litre.
Bulk de nsity =
net weight of the aggregate in kg
capacity of the container in litre
Percentage of voids = Gs − γ × 100
Gs

Where, Gs = specific gravity of aggregate and

γ = bulk density in kg/litre

MECHANICAL PROPERTIES OF AGGREGATES IS: 2386 PART IV – 1963

Test for determination of aggregate crushing value

The “aggregate crushing value” gives a relative measure of the resistance of an aggregate to crushing
under a gradually applied compressive load. With aggregates of ‘aggregate crushing value’ 30 or
higher, the result may be anomalous and in such cases the “ten per cent fines value” should be
determined and used instead.

The standard aggregate crushing test is made on aggregate passing a 12.5 mm I.S. Sieve and retained
on 10 mm I.S. Sieve.

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Dept. of Civil Engineering, MEAEC Module II
About 6.5 kg material consisting of aggregates passing 12.5 mm and retained on 10 mm sieve is
taken. The aggregate in a surface dry condition is filled into the standard cylindrical measure in three
layers approximately of equal depth. Each layer is tamped 25 times with the tamping rod and finally
levelled off using the tamping rod as straight edge. The weight of the sample contained in the cylinder
measure is taken (A). The same weight of the sample is taken for the subsequent repeat test.

Aggregate Crushing Value Apparatus

The apparatus, with the test sample and plunger in position, is placed on the compression testing
machine and is loaded uniformly upto a total load of 40 tons in 10 minutes time. The load is then
released and the whole of the material removed from the cylinder and sieved on a 2.36 mm I.S. Sieve.
The fraction passing the sieve is weighed (B),
B
The aggregate crushing value = A × 100

where, B = weight of fraction passing 2.36 mm sieve,

A = weight of surface-dry sample taken in mould.

The aggregate crushing value should not be more than 45 per cent for aggregate used for concrete
other than for wearing surfaces, and 30 per cent for concrete used for wearing surfaces such a
runways, roads and air field pavements.

Test for determination of aggregate impact value

The aggregate impact value gives relative measure of the resistance of an aggregate to sudden shock
or impact. Which in some aggregates differs from its resistance to a slow compressive load.

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Module II Dept. of Civil Engineering, MEAEC

Aggregate Impact Value Apparatus

The test sample consists of aggregate passing through 12.5 mm and retained on 10 mm I.S. Sieve. The
aggregate shall be dried in an oven for a period of four hours at a temperature of 100°C to 110°C and
cooled. The aggregate is filled about one-third full and tamped with 25 strokes by the tamping rod. A
further similar quantity of aggregate is added and tamped in the standard manner. The measure is
filled to over-flowing and then struck off level. The net weight of the aggregate in the measure is
determined (weight A) and this weight of aggregate shall be used for the duplicate test on the same
material.

The whole sample is filled into a cylindrical steel cup firmly fixed on the base of the machine. A
hammer weighing about 14 kg is raised to a height of 380 mm above the upper surface of the
aggregate in the cup and allowed to fall freely on the aggregate. The test sample shall be subjected to
a total 15 such blows each being delivered at an interval of not less than one second. The crushed
aggregate is removed from the cup and the whole of it is sieved on 2.36 mm I.S. Sieve. The fraction
passing the sieve is weighed to an accuracy of 0.1 gm. (weight B). The fraction retained on the sieve is
also weighed (weight C). If the total weight (B + C) is less than the initial weight A by more than one
gm the result shall be discarded and a fresh test made. Two tests are made.

The ratio of the weight of fines formed to the total sample weight in each test is expressed as
percentage.
B
The aggregate crushing value = A × 100

where, B = weight of fraction passing 2.36 mm sieve,

A = weight of surface-dry sample taken in mould.

The aggregate impact value should not be more than 45 per cent by weight for aggregates used for
concrete other than wearing surfaces and 30 per cent by weight for concrete to be used as wearing
surfaces, such as runways, roads and pavements.

Test for determination of aggregate abrasion value

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 Dept. of Civil Engineering, MEAEC Module II
Apart from testing aggregate with respect to its crushing value, impact resistance, testing the
aggregate with respect to its resistance to wear is an important test for aggregate to be used for road
constructions, ware house floors and pavement construction.

Indian Standard 2386 (Part IV) of 1963 covers two methods for finding out the abrasion value of
coarse aggregates: namely, by the use of Deval abrasion testing machine and by the use of Los
Angeles abrasion testing machine. However, the use of Los Angeles abrasion testing machine gives a
better realistic picture of the abrasion resistance of the aggregate.

Deval Attrition Test

In the Deval attrition test, particles of known weight are subjected to wear in an iron cylinder rotated
10000 times at certain speed. The proportion of material crushed finer than 1.7 mm size is expressed
as a percentage of the original material taken. This percentage is taken as the attrition value of the
aggregate. This test has been covered by IS 2386 (Part IV) – 1963. But it is pointed out that wherever
possible Los Angeles test should be used.

Deval’s Attrition testing machine

  Well dried (at 100-110⁰C) aggregate samples of size 5cm is taken in two cylinders
  Rotate the aggregates together for about 5hrs at a speed of 30-1000rpm
  Aggregates loss their weight due to rubbing action among the aggregates
  Note the percentage loss in weight of aggregates
 Greater loss in weight, poorer is resistance to abrasion
Los Angeles Test

Los Angeles test was developed to overcome some of the defects found in Deval test. Los Angeles
test is characterized by the quickness with which a sample of aggregate may be tested. The
applicability of the method to all types of commonly used aggregate makes this method popular. The
test involves taking specified quantity of standard size material along with specified number of
abrasive charge in a standard cylinder and revolving if for certain specified revolutions.

Los Angeles Abrasion Testing Machine

CE 204 – Construction Technology 2.15 | Page

Module II Dept. of Civil Engineering, MEAEC
Test sample and abrasive charge are placed in the Los Angeles Abrasion testing machine and the
machine is rotated at a speed of 20 to 33 rev/min. At the completion of revolution, the material is
discharged from the machine and a preliminary separation of the sample made on a sieve coarser
than 1.7 mm IS Sieve. Finer portion is then sieved on a 1.7 mm IS Sieve. The material coarser than 1.7
mm IS sieved is washed, dried in an oven at 105° to 110°C to a substantially constant weight and
accurately weighed to the nearest gram.

The difference between the original weight and the final weight of the test sample is expressed as a
percentage of the original weight of the test sample. This value is reported as the percentage of
wear. The abrasion value should not be more than 30 per cent for wearing surfaces and not more
than 50 per cent for concrete other than wearing surface.

WATER
Water is an essential ingredient of concrete. It hydrate cement and imparts binding property in the
cement paste.

Water activates the hydration of cement and forms a plastic mass also gives workability to concrete,
that is, it makes the concrete easy to mix so that it can be placed in its final position. More the water,
better is the workability. However excess water reduces the strength of concrete. Figure shows the
variation of strength of concrete with water cement ratio.

Relationship between compressive strength and water-cement ratio

In order to achieve required workability and good strength at the same time, a water - cement ratio
of 0.4 -0.5 is used in case of machine mixing while in case of hand mixing, a water - cement ratio of
0.5 - 0.6 is used.

Water normally contains the following types of impurities:

(a) Organic (c) Sulphate
(b) Inorganic (d) Chloride
(e) Suspended matter

As per IS: 456 -2000, permissible limit of impurities in water to be used for concrete is as given
in Table below.

S.No Impurity Permissible Limit

1. Organic 200 mg/L
2. Inorganic 3000 mg/L
3. Sulphate 400mg/L
4. Chloride 2000 mg/L for plain Concrete 500 mg/L for R.C.C
5. Suspended 2000 mg/L

In general potable water is to be used for making and curing of concrete.

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 Dept. of Civil Engineering, MEAEC Module II
ADMIXTURES
Admixture is an optional ingredient of concrete. The admixture is a material added to concrete mix at
the time of making concrete. The purpose of using admixtures is to impart special properties to
concrete to meet different situations or to reduce the cost of concrete

Admixtures may be broadly grouped into two categories, Viz. mineral additives and chemical
additives.

Mineral admixtures

These admixtures do not have any binding property by themselves but they react with calcium
hydroxide liberated on hydration of cement and produce cementing compound. They are cheap and
added in large quantities, hence they reduce cost of concrete per unit volume.

Mineral admixtures are known as pozzolanic materials also. Commonly used pozzolanic materials are
fly ash, silica fumes, ground granulated blast furnace slag (GGBFS), surkhi, rice-husk and Metakaolin.

Fly ash is a waste product produced in thermal power stations. Silica fume is a byproduct during the
manufacture of silicon. Ground Granulated Blast Furnace Slag (GGBFS) is byproduct in the production
of iron. Surkhi is an artificial pozzolana obtained by burning brickbats or clay balls. Rice Husk ash is
produced by burning rice husk. Metakaolin is fine clay which is traditionally known as china clay.

The addition of pozzolanic materials modify the properties of the concrete as given below:

  Improves workability.
  Increases water tightness.
  Improves resistance to sulphate attack.
  Lowers the heat of hydration and hence, thermal shrinkage.
 Lowes the cost of concrete.

Chemical admixtures

When these admixtures are added to concrete mix, they spread throughout the body of concrete and
chemically react to impart special properties These chemical are generally available in the liquid form
in bottles. Only small quantities of chemical admixtures are to be added to the water used for making
concrete. The following are the commonly used chemical admixtures.

(a) Accelerators
(b) Retarders
(c) Water reducing agents / Plasticizers
(d) Air entraining agents.

(a) Accelerators

The accelerators are used to speed up the setting of concrete and gain early strength. The advantage
of using these admixtures are

  Formwork can be removed early

  Curing period is reduced
 The structure can be put to use early.

CE 204 – Construction Technology 2.17 | Page

Module II Dept. of Civil Engineering, MEAEC
Accelerators are preferred in
  Construction of high rise buildings
  For repair works
 For cold weather concreting.

Commonly used retarder are

  Calcium chloride (CaCl2)
  Fluro - silicate
  Sodium compounds like NaCl, Na2SO4, NaOH, Na2CO3
 Potassium compounds like K2S04, KOH.

(b) Retarders

Retarder slow down initial rate of hydration and hence extend initial setting time. Initial setting time
may be delayed by 3 to 4 hours. Retarders are used in the following situations.
  For grouting deep oil wells
  For transporting ready mixed concrete (RMC) for long distances and congested streets.
 To avoid cold joints, if there is going to be breaks in the process of concreting.

The following are the chemical retarders:

  Calcium sulphate (Gypsum)
  Soluble carbohydrates like sugar, starch, cellulose products
  Hydroxylated carboxylic acids and their salt
 Sulphuric acids and their salts.

(c) Water reducing agents / plasticizes

Water - cement ratio 0.3 is enough for hydration. But to get suitable workability water cement ratio
of 0.45 is used for machine mixing and up to 0.55 to 0.6 for han4 mixing. It is well known fact that
increase in water - cement ratio results in decrease in strength of concrete. Hence there is need to
achieve good workability without increasing the water content. The admixtures which fulfill this
objective are called plasticizers.

Plasticizes are classified on the basis of their capacity to reduce water content, without reducing
workability as shown below:

  Normal water reducers - reducing 5 to 10 percent.

  Mid - range water reducers - reducing 10 to 20 percent.
 High range water reducers- reducing 10 to 40 percent (Super Plasticizers).

Organic or synthetic raw materials are normal water reducers, Hydroxylated carboxylic acids and
their salt, lingo sulphate acids and their salts are midrange water reducers. Sulphonated melamine -
formaldehyde, modified lingo sulphonates are the super plasticizers.

For the benefit of users, manufacturers of plasticizers give the following instructions.

  Grade of concrete up to which it is to be used.

  Percentage of water -cement ratio it can reduce.
  Dosage to be used for 50kg bag of cement.
 Maximum time period within which concrete should be placed.

In all major works, it is recommended that the above recommendations are verified by the users.
2.18 | Page CE 204 – Construction Technology
 Dept. of Civil Engineering, MEAEC Module II
(d) Air entraining agents

These agents help to incorporate a controlled amount of air in the form of millions of minute bubbles,
distributed throughout the body of concrete. These agents are added during mixing of concrete or
while manufacturing the cement. They do not alter significantly the setting or the rate of hardening of
concrete.

Advantages of using Air – entraining agents are:

 It increases resistance to freezing and thawing. Air bubbles absorb change in volume due to
 freezing.
  Air bubbles act as lubricants in the mix and hence improve workability.
  The air bubbles reduce segregation and bleeding.
 There is improvement in water tightness and resistance to chemical attack.

 Compared to ordinary concrete of the same strength and workability air entrained concrete
shows about 5 percent less weight per unit volume. Hence dead load on the structure is
reduced.

 As bleeding, segregation and surface cracking are reduced, the exposed surface of air
entrained concrete is unifor1n and smooth.

The following are the adverse effects of air – entrainment

 The compressive strength of air entrained concrete is less than ordinary concrete. However
the advantage gained by reduction in water-cement ratio for the same workability reduces
this adverse effect to some extent.

 The modulus of elasticity of air entrained concrete is reduced by 2 to 3 percent for each
percent of air entrainment.

 The Abrasion resistance of air entrained concrete is not affected up to 6 percent, the abrasion
resistance reduces gradually. At about .10 percent abrasion resistance is markedly reduced.

Precautions to be taken in using Admixtures

IS : 456 - 2000 suggests the following precautions are to be taken while using any admixture:

  Admixture should comply with IS: 9103

  It should not impair durability.
  It should not combine with the constituent to form harmful compounds.
 It should not increase chances of corrosion of steel in R.C.C.

 With trial mixes, the effect of admixture on workability, compressive strength and the slump
loss should be studied.

 The relative density of liquid admixtures should be checked for each drum containing
 admixtures.
 For each batch, the chloride content of admixtures should be checked.

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Module II Dept. of Civil Engineering, MEAEC

STORAGE OF CEMENT

Store Godown

Since cement is hygroscopic is nature, it loses strength with time depending upon its exposure to
moisture. Therefore in order to minimize the loss of strength, the following precautions should be
taken while storing the cement in Godown.

  Godown should be air tight and moisture proof and above the ground level as shown in Fig above
 Bags should be stacked on raised platform

 Different stacks should be made for different cement company, date of manufacture, type and
grade of cement. In addition identification tags should be displayed on each stack showing all
above details.

 There should be a clearance of about 0.6 m between adjacent stacks and also outer walls and
the stacks as shown below

 Normally not more than 7-8 bags should be stacked vertically. Up to 15 bags can be permitted
 temporarily. Efforts should be made to remove additional bags as early as possible.
  During rainy season, the stacks should be covered with 700 gauge polythene sheets.
 For general purpose First in - First out policy should be adopted.

GAIN OF STRENGTH IN CEMENT

Initially the rate of gain of strength in the cement is very high but it reduces with time. However, the
process of strength gain continues forever. The strength gain is faster in the beginning mainly
because of the following reasons

  Prompt response of more active constituents

  Rapid hydration of finer particles of the cement
 Ready availability of a lot of free water

As outer layers start setting, the availability of water reduces for the inner particles and the rate of
gain of strength decreases.

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Dept. of Civil Engineering, MEAEC Module II
PROCESS OF MANUFACTURE OF CONCRETE
Production of quality concrete requires more care exercised at every stage of manufacture of concrete. It
is necessary for us to know what are the good rules to be followed in each stage of manufacture of
concrete for producing good quality concrete. The various stages of manufacture of concrete are:

(a) Batching (e) Compacting

(b) Mixing (f) Curing
(c) Transporting (g) Finishing.
(d) Placing
(a) BATCHING

The measurement of materials for making concrete is known as batching. There are two methods of
batching:
i. Volume batching
ii. Weigh batching

(i) Volume batching: Volume batching is not a good method for proportioning the material because
of the difficulty it offers to measure granular material in terms of volume. The amount of solid
granular material in a cubic meter is an indefinite quantity. Because of this, for quality concrete
material has to be measured by weight only. However, for unimportant concrete or for any small job,
concrete may be batched by volume.

Cement is always measured by weight. It is never

measured in volume. Generally, for each batch mix, one
bag of cement is used. The volume of one bag of cement
is taken as thirty five (35) litres. Gauge boxes are used for
measuring the fine and coarse aggregates. The typical
sketch of a guage box is shown in Figure The volume of
the box is made equal to the volume of one bag of
cement i.e., 35 litres or multiple thereof. Gauge boxes
are generally called farmas. They can be made of timber
or steel plates. Often in India volume batching is adopted
even for large concreting operations.

(ii) Weigh Batching: Strictly speaking, weigh batching is the correct method of measuring the
materials. For important concrete, invariably, weigh batching system should be adopted.

Use of weight system in batching, facilitates accuracy, flexibility and simplicity. Different types of
weigh batchers are available, in some of the recent automatic weigh batching equipment, recorders
are fitted which record graphically the weight of each material, delivered to each batch. They are
meant to record, and check the actual and designed proportions.
(b) MIXING

Thorough mixing of the materials is essential for the production of uniform concrete. The mixing
should ensure that the mass becomes homogeneous, uniform in colour and consistency. There are
two methods adopted for mixing concrete:
i. Hand mixing ii. (ii) Machine mixing

(i) Hand Mixing: Hand mixing is practiced for small scale unimportant concrete works. As the mixing
cannot be thorough and efficient, it is desirable to add 10 per cent more cement to cater for the
inferior concrete produced by this method.

Hand mixing should be done over an impervious concrete or brick floor of sufficiently large size to
take one bag of cement. Spread out the measured quantity of coarse aggregate and fine aggregate in
alternate layers. Pour the cement on the top of it, and mix them dry by shovel, turning the mixture

CE 204 – Construction Technology 2.21 | Page

Module II Dept. of Civil Engineering, MEAEC
over and over again until uniformity of colour is achieved. This uniform mixture is spread out in thickness
of about 20 cm. Water is taken in a water-can fitted with a rose-head and sprinkled over the mixture and
simultaneously turned over. This operation is continued till such time a good uniform, homogeneous
concrete is obtained. It is of particular importance to see that the water is not poured but it is only
sprinkled. Water in small quantity should be added towards the end of the mixing to get the just required
consistency. At that stage, even a small quantity of water makes difference.

(ii) Machine Mixing: Mixing of concrete is almost invariably carried out by machine, for reinforced
concrete work and for medium or large scale mass concrete work. Machine mixing is not only
efficient, but also economical, when the quantity of concrete to be produced is large.

Many types of mixers are available for mixing concrete. They can be classified as batch-mixers and
continuous mixers. Batch mixers produce concrete, batch by batch with time interval, whereas
continuous mixers produce concrete continuously without stoppage till such time the plant is
working. In this, materials are fed continuously by screw feeders and the materials are continuously
mixed and continuously discharged. This type of mixers is used in large works such as dams. In normal
concrete work, it is the batch mixers that are used.

Batch mixer may be of pan type or drum type. The drum type may be further classified as tilting, non-
tilting, reversing or forced action type.

As per I.S. 1791–1985, concrete mixers are designated by a number representing its nominal mixed
batch capacity in litres. The following are the standardized sizes of three types:
a. Tilting: 85 T, 100 T, 140 T, 200 T
b. Non-Tilting: 200 NT, 280 NT, 375 NT, 500 NT, 1000 NT
c. Reversing: 200 R, 280 R, 375 R, 500 R and 1000 R

The letters T, NT, R denote tilting, non-tilting and reversing respectively. A batch of concrete is made
with ingredients corresponding to 50 kg cement. If one has a choice for indenting a mixer, one should
ask for such a capacity mixer that should hold all the materials for one bag of cement. This of course,
depends on the proportion of the mix. For example, for 1: 2: 4 mix, the ideal mixer is of 200 litres
capacity, whereas if the ratio is 1: 3: 6, the requirement will be of 280 litres capacity to facilitate one
bag mix. Mixer of 200 litres capacity is insufficient for 1: 3: 6 mix and also mixer of 280 litres is too
big, hence uneconomical for 1: 2: 4 concrete.
To get better efficiency, the sequence of charging the loading skip is as under:

Firstly, about half the quantity of coarse aggregate is placed in the skip over which about half the
quantity of fine aggregate is poured. On that, the full quantity of cement i.e., one bag is poured over
which the remaining portion of coarse aggregate and fine aggregate is deposited in sequence. This
prevents spilling of cement, while discharging into the drum and also this prevents the blowing away
of cement in windy weather.

Before the loaded skip is discharged to the drum, about 25 per cent of the total quantity of water
required for mixing is introduced into the mixer drum to wet the drum and to prevent any cement
sticking to the blades or at the bottom of the drum. Immediately, on discharging the dry material into
the drum, the remaining 75 per cent of water is added to the drum. If the mixer has got an
arrangement for independent feeding of water, it is desirable that the remaining 75 per cent of water
is admitted simultaneously along with the other materials. The time is counted from the moment all
the materials, particularly; the complete quantity of water is fed into the drum.

When plasticizer or super plasticizer is used, the usual procedure could be adopted except that about
one litre of water is held back. Calculated quantity of plasticizer or super plasticizer is mixed with that
one litre of water and the same is added to the mixer drum after about one minute of mixing.

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Dept. of Civil Engineering, MEAEC Module II
(C) TRANSPORTING CONCRETE

Concrete can be transported by a variety of methods and equipment. The precaution to be taken
while transporting concrete is that the homogeneity obtained at the time of mixing should be
maintained while being transported to the final place of deposition. The methods adopted for
transportation of concrete are:
i. Mortar Pan v. Belt Conveyors
ii. Wheel Barrow, Hand Cart vi. Chute
iii. Crane, Bucket and Rope way vii. Skip and Hoist
iv. Truck Mixer and Dumpers viii. Tansit Mixer

Mortar Pan: Use of mortar pan for transportation of concrete is one of the common methods
adopted in this country. It is labour intensive. In this case, concrete is carried in
small quantities. While this method nullifies the segregation to some
extent, particularly in thick members, it suffers from the disadvantage that
this method exposes greater surface area of concrete for drying conditions.
It is to be noted that the mortar pans must be wetted to start with and it
must be kept clean during the entire operation of concreting.

Wheel Barrow: Wheel barrows are normally used for transporting

concrete to be placed at ground level. This method is employed for
hauling concrete for comparatively longer distance as in the case of
concrete road construction. If concrete is conveyed by wheel barrow
over a long distance, on rough ground, it is likely that the concrete gets
segregated due to vibration

Crane, Bucket and Rope Way: A crane and bucket is one of the right equipment for transporting
concrete above ground level. Cranes are fast and versatile to move concrete horizontally as well as
vertically along the boom and allows the placement of concrete at the exact point. Cranes carry skips
or buckets containing concrete. Skips have discharge door at the bottom, whereas buckets are tilted
3
for emptying. For a medium scale job the bucket capacity may be 0.5 m .
Rope way and bucket of various sizes are used for transporting concrete to a place, where simple
method of transporting concrete is found not feasible. For the concrete works in a valley or the
construction work of a pier in the river or for dam construction, this method of transporting by rope
way and bucket is adopted. The mixing of concrete is done on the bank or abutment at a convenient
place and the bucket is brought by a pulley or some other arrangement. It is filled up and then taken
away to any point that is required. The vertical movement of the bucket is also controlled by another
set of pullies. This is one of the methods generally adopted for concreting dam work or bridge work.

Truck Mixer and Dumpers: For large concrete works particularly for concrete to be placed at ground
level, trucks and dumpers or ordinary open steel-body tipping Lorries can be used.

Dumpers are of usually 2 to 3 cubic metre capacity, whereas the

capacity of truck may be 4 cubic metre or more. Before loading
with the concrete, the inside of the body should be just wetted
with water. Tarpaulins or other covers may be provided to cover
the wet concrete during transit to prevent evaporation. When
the haul is long, it is advisable to use agitators which prevent
segregation and stiffening. The agitators help the mixing process
at a slow speed.

For road construction using Slip Form Paver large quantity of concrete is required to be supplied
continuously. A number of dumpers of 6 m3 capacity are employed to supply concrete. Small dumper
called Tough Riders are used for factory floor construction.
Belt Conveyors: Belt conveyors have very limited applications in concrete construction.

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Module II Dept. of Civil Engineering, MEAEC
The principal objection is the tendency of the concrete to segregate on steep inclines, at transfer
points or change of direction, and at the points where the belt passes over the rollers.

Another disadvantage is that the concrete is exposed over long stretches which causes drying and
stiffening particularly, in hot, dry and windy weather. Segregation also takes place due to the
vibration of rubber belt. It is necessary that the concrete should be remixed at the end of delivery
before placing on the final position. In adverse weather conditions (hot and windy) long reaches of
belt must be covered.

Chute: Chutes are generally provided for transporting concrete from

ground level to a lower level.

The sections of chute should be made of or lined with metal and all runs
shall have approximately the same slope, not flatter than 1 vertical to 2
1/2 horizontal. The lay-out is made in such a way that the concrete will
slide evenly in a compact mass without any separation or segregation.

Skip and Hoist: This is one of the widely adopted methods for transporting concrete vertically up for
multi storey building construction. Employing mortar pan with the staging and human ladder for
transporting concrete is not normally possible for more than 3 or 4 storeyed building constructions.
For laying concrete in taller structures, chain hoist or platform hoist or skip hoist is adopted.

At the ground level, mixer directly feeds the skip and the skip
travels up over rails upto the level where concrete is required.
At that point, the skip discharges the concrete automatically or
on manual operation. The quality of concrete i.e. the freedom
from segregation will depend upon the extent of travel and
rolling over the rails. If the concrete has travelled a
considerable height, it is necessary that concrete on discharge
is required to be turned over before being placed finally.

Transit Mixer: Transit mixer is one of the most popular equipment for transporting concrete over a
long distance particularly in Ready Mixed Concrete plant (RMC).
3
They are truck mounted having a capacity of 4 to 7 m . There are
two variations. In one, mixed concrete is transported to the site by
keeping it agitated all along at a speed varying between 2 to
6 revolutions per minute. In the other category, the concrete is
batched at the central batching plant and mixing is done in the
truck mixer either in transit or immediately prior to discharging
the concrete at site. Transit-mixing permits longer haul and is
less vulnerable in case of delay. The truck mixer the speed of
rotating of drum is between4–16 revolution per minute.
(d) PLACING CONCRETE

It is not enough that a concrete mix correctly designed, batched, mixed and transported, it is of
utmost importance that the concrete must be placed in systematic manner to yield optimum results.
Concrete is invariably laid as foundation bed below the walls or columns.
Foundations:

Before placing the concrete in the foundation, all the loose earth must be removed from the bed. Any
root of trees passing through the foundation must be cut, charred or tarred effectively to prevent its
further growth and piercing the concrete at a later date. The surface of the earth, if dry, must be just
made damp so that the earth does not absorb water from concrete. On the other hand if the foundation
bed is too wet and rain-soaked, the water and slush must be removed completely to exposé firm bed
before placing concrete. If there is any seepage of water taking place into the foundation

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Dept. of Civil Engineering, MEAEC Module II
trench, effective method for diverting the flow of water must be adopted before concrete is placed in
the trench or pit.
Road Slabs

For the construction of road slabs, airfield slabs and ground floor slabs in buildings, concrete is placed
in bays. The ground surface on which the concrete is placed must be free from loose earth, pool of
water and other organic matters like grass, roots, leaves etc.

The earth must be properly compacted and made sufficiently damp to prevent the absorption of
water from concrete. If this is not done, the bottom portion of concrete is likely to become weak.
Sometimes, to prevent absorption of moisture from concrete, by the large surface of earth, in case of
thin road slabs, use of polyethylene film is used in between concrete and ground. Concrete is laid in
alternative bays giving enough scope for the concrete to undergo sufficient shrinkage. It must be
remembered that the concrete must be dumped and not poured. The practice of placing concrete in a
heap at one place and then dragging it should be avoided.
Concrete Piers

When concrete is laid in great thickness, as in the case of concrete raft for a high rise building or in
the construction of concrete pier or abutment or in the construction of mass concrete dam, concrete
is placed in layers. The thickness of layers depends upon the mode of compaction.

In reinforced concrete, it is a good practice to place concrete in layers of about 15 to 30 cm thick and
in mass concrete, the thickness of layer may vary between 35 to 45 cm. Several such layers may be
placed in succession to form one lift, provided they follow one another quickly enough to avoid cold
joints. The thickness of layer is limited by the method of compaction and size and frequency of
vibrator used.

Before placing the concrete, the surface of the previous lift is cleaned thoroughly with water jet and
scrubbing by wire brush. In case of dam, even sand blasting is also adopted. The old surface is
sometimes hacked and made rough by removing all the laitance and loose material. The surface is
wetted. Sometimes, a neat cement slurry or a very thin layer of rich mortar with fine sand is dashed
against the old surface, and then the fresh concrete is placed.

The whole operation must be progressed and arranged in such a way that, cold joints are avoided as
far as possible. When concrete is laid in layers, it is better to leave the top of the layer rough, so that
the succeeding layer can have a good bond with the previous layer.
Formwork

Certain good rules should be observed while placing concrete within the formwork, as in the case of
beams and columns. Firstly, it must be checked that the reinforcement is correctly tied, placed and is
having appropriate cover. The joints between planks, plywood or sheets must be properly and
effectively plugged so that matrix will not escape when the concrete is vibrated. The inside of the
formwork should be applied with mould releasing agents for easy stripping. Such purpose made
mould releasing agents are separately available for steel or timber shuttering. The reinforcement
should be clean and free from oil.

Where reinforcement is placed in a congested manner, the concrete must be placed very
carefully, in small quantity at a time so that it does not block the entry of subsequent concrete. The
above situation often takes place in heavily reinforced concrete columns with close lateral ties, at the
junction of column and beam and in deep beams. Generally, difficulties are experienced for placing
concrete in the column.

Often concrete is required to be poured from a greater height. When the concrete is poured from
a height, against reinforcement and lateral ties, it is likely to segregate or block the space to prevent
further entry of concrete. To avoid this, concrete is directed by tremie, drop chute or by any other means
to direct the concrete within the reinforcement and ties. Sometimes, when the formwork

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Module II Dept. of Civil Engineering, MEAEC
is too narrow, or reinforcement is too congested to allow the use of tremie or drop chute, a small
opening in one of the sides is made and the concrete is introduced from this opening instead of
pouring from the top.
Underwater Concreting

The satisfactory method of placing concrete under water is

by the use of tremie pipe. A tremie pipe is a pipe having a diameter
of about 20 cm capable of easy coupling for increase or decrease of
length. A funnel is fitted to the top end to facilitate pouring of
concrete. The bottom end is closed with a plug or thick polyethylene
sheet or such other material and taken below the water and made to
rest at the point where the concrete is going to be placed. Since the
end is blocked, no water will have entered the pipe.

The concrete having a very high slump of about 15 to 20 cm is

poured into the funnel. When the whole length of pipe is filled up with
the concrete, the tremie pipe is lifted up and a slight jerk is given by a
winch and pully arrangement. When the pipe is raised and given a jerk,
due to the weight of concrete, the bottom plug falls and the concrete
gets discharged. Particular care must be taken at this stage to see that
the end of the tremie pipe remains inside the concrete, so
that no water enters into the pipe from the bottom. In other words, the tremie pipe remains plugged
at the lower end by concrete.
Slip-Form Technique

There are special methods of placement of concrete using slip-form technique. Slip forming can be
done both for vertical construction or horizontal construction.

Slip-forming of vertical construction is a proven method of concrete construction generally adopted

for tall structures. In this method, concrete is continuously placed, compacted and formwork is pulled
up by number of hydraulic Jacks, giving reaction, against jack rods or main reinforcements. The rate
of slipping the formwork will vary depending upon the temperature and strength development of
concrete to withstand without the support of formwork. In India number of tall structures like
chimneys and silos have been built by this technique.

The horizontal slip-form construction is rather a new

technique in India. It is adopted for road pavement
construction. Slip-form paver is a major equipment,
capable of spreading the concrete dumped in front of the
machine by tippers or dumpers, compacting the concrete
through number of powerful internal needle vibrators and
double beam surface vibrators. The paver carries out the
smooth finishing operation to the highest accuracy and
then texture the surface with nylon brush operating
across the lane. The equipment also drops the tie bar at
the predetermined interval and push them through and
places them at the predetermined depth
and re-compact the concrete to cover up the gap that are created by the dowel bars.
(e) COMPACTION OF CONCRETE

Compaction of concrete is the process adopted for expelling the entrapped air from the concrete. In
the process of mixing, transporting and placing of concrete air is likely to get entrapped in the
concrete. The lower the workability, higher is the amount of air entrapped.

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Dept. of Civil Engineering, MEAEC Module II
In other words, stiff concrete mix has high percentage of entrapped air and, therefore, would need
higher compacting efforts than high workable mixes.
The following methods are adopted for compacting the concrete:
(1) Hand Compaction
i. Rodding
ii. Ramming
iii. Tamping
(2) Compaction by Vibration
i. Internal vibrator (Needle vibrator)
ii. Formwork vibrator (External vibrator)
iii. Table vibrator
iv. Platform vibrator
v. Surface vibrator (Screed vibrator)
vi. Vibratory Roller.
Hand Compaction:

Hand compaction of concrete is adopted in case of unimportant concrete work of small magnitude.
Sometimes, this method is also applied in such situation, where a large quantity of reinforcement is
used, which cannot be normally compacted by mechanical means. Hand compaction consists of
rodding, ramming or tamping. When hand compaction is adopted, the consistency of concrete is
maintained at a higher level. The thickness of the layer of concrete is limited to about 15 to 20 cm.

Rodding is nothing but poking the concrete with about 2 metre long, 16 mm diameter rod to pack the
concrete between the reinforcement and sharp corners and edges. Rodding is done continuously
over the complete area to effectively pack the concrete and drive away entrapped air. Sometimes,
instead of iron rod, bamboos or cane is also used for rodding purpose.

Ramming should be done with care. Light ramming can be permitted in unreinforced foundation
concrete or in ground floor construction. Ramming should not be permitted in case of reinforced
concrete or in the upper floor construction, where concrete is placed in the formwork supported on
struts. If ramming is adopted in the above case the position of the reinforcement may be disturbed or
the formwork may fail, particularly, if steel rammer is used.

Tamping is one of the usual methods adopted in compacting roof or floor slab or road pavements
where the thickness of concrete is comparatively less and the surface to be finished smooth and level.
Tamping consists of beating the top surface by wooden cross beam of section about 10 x 10 cm. Since
the tamping bar is sufficiently long it not only compacts, but also levels the top surface across the
entire width.
Compaction by Vibration:

Where high strength is required, it is necessary that stiff concrete, with low water/cement ratio be
used. To compact such concrete, mechanically operated vibratory equipment, must be used. The
vibrated concrete with low water/cement ratio will have many advantages over the hand compacted
concrete with higher water/cement ratio.

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Module II Dept. of Civil Engineering, MEAEC

Internal Vibrator: Of all the vibrators, the internal vibrator is most commonly used. This is also called,
“Needle Vibrator”, “Immersion Vibrator”, or “Poker Vibrator”. This essentially consists of a power
unit, a flexible shaft and a needle. The power unit may be electrically driven or operated by petrol
engine or air compressor. The vibrations are caused by eccentric weights attached to the shaft or the
motor or to the rotor of a vibrating element. They are portable and can be shifted from place to place
very easily during concreting operation. They can also be used in difficult positions and situations.

Formwork Vibrator (External Vibrator): Formwork vibrators are used for concreting columns, thin
walls or in the casting of precast units. The machine is clamped on to the external wall surface of the
formwork. The vibration is given to the formwork so that the concrete in the vicinity of the shutter
gets vibrated. This method of vibrating concrete is particularly useful and adopted where
reinforcement, lateral ties and spacers interfere too much with the internal vibrator. Use of
formwork vibrator will produce a good finish to the concrete surface. Since the vibration is given to
the concrete indirectly through the formwork, they consume more power and the efficiency of
external vibrator is lower than the efficiency of internal vibrator.

Table Vibrator: This is the special case of formwork vibrator, where the vibrator is clamped to the
table or table is mounted on springs which are vibrated transferring the vibration to the table. They
are commonly used for vibrating concrete cubes. Any article kept on the table gets vibrated.
This is adopted mostly in the laboratories and in making small but precise prefabricated R.C.C.
members.

Platform Vibrator: Platform vibrator is nothing but a table vibrator, but it is larger in size. This is used
in the manufacture of large prefabricated concrete elements such as electric poles, railway sleepers,
prefabricated roofing elements etc. Sometimes, the platform vibrator is also coupled with jerking or
shock giving arrangements such that a thorough compaction is given to the concrete.

Surface Vibrator: Surface vibrators are sometimes known as, “Screed Board Vibrators”. A small vibrator
placed on the screed board gives an effective method of compacting and levelling of thin concrete
members, such as floor slabs, roof slabs and road surface. Mostly, floor slabs and roof slabs are so thin
that internal vibrator or any other type of vibrator cannot be easily employed. In such cases, the surface
vibrator can be effectively used. In general, surface vibrators are not effective beyond about 15 cm.

(f) CURING OF CONCRETE

Concrete derives its strength by the hydration of cement particles. The hydration of cement is not a
momentary action but a process continuing for long time. The curing can be considered as creation of
a favourable environment during the early period forum interrupted hydration. The desirable
conditions are a suitable temperature and ample moisture. Curing can also be described as keeping
the concrete moist and warm enough so that the hydration of cement can continue. More
elaborately, it can be described as the process of maintaining satisfactory moisture content and a
favourable temperature in concrete during the period immediately following placement, so that
hydration of cement may continue until the desired properties are developed to a sufficient degree
to meet the requirement of service.
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Dept. of Civil Engineering, MEAEC Module II
Curing Methods
Curing methods may be divided broadly into four categories:
(a) Water curing (b) Membrane curing (c ) Application of heat (d) Miscellaneous
Water Curing

This is by far the best method of curing as it satisfies all the requirements of curing, namely, promotion of
hydration, elimination of shrinkage and absorption of the heat of hydration. It is pointed out that even if
the membrane method is adopted, it is desirable that a certain extent of water curing is done before the
concrete is covered with membranes. Water curing can be done in the following ways:

i. Immersion
ii. Ponding
iii. Spraying or Fogging
iv. Wet covering

The precast concrete items are normally immersed in curing tanks for a certain duration. Pavement
slabs, roof slab etc. are covered under water by making small ponds. Vertical retaining wall or
plastered surfaces or concrete columns etc. are cured by spraying water. In some cases, wet
coverings such as wet gunny bags, hessian cloth, jute matting, straw etc., are wrapped to vertical
surface for keeping the concrete wet. For horizontal surfaces saw dust, earth or sand are used as wet
covering to keep the concrete in wet condition for a longer time so that the concrete is not unduly
dried to prevent hydration.
Membrane Curing

Sometimes, concrete works are carried out in places where there is acute shortage of water. The
lavish application of water for water curing is not possible for reasons of economy.

For this reason, concrete could be covered with membrane which will effectively seal off the
evaporation of water from concrete. It is found that the application of membrane or a sealing
compound, after a short spell of water curing for one or two days is sometimes beneficial.

Sometimes, concrete is placed in some inaccessible, difficult or far off places. The curing of such
concrete cannot be properly supervised. The curing is entirely left to the workmen, who do not quite
understand the importance of regular uninterrupted curing. In such cases, it is much safer to adopt
membrane curing rather than to leave the responsibility of curing to workers.

Large number of sealing compounds has been developed in recent years. The idea is to obtain a
continuous seal over the concrete surface by means of a firm impervious film to prevent moisture in
concrete from escaping by evaporation. Sometimes, such films have been used at the interface of the
ground and concrete to prevent the absorption of water by the ground from the concrete. Some of
the materials that can be used for this purpose are bituminous compounds, polyethylene or polyester
film, waterproof paper, rubber compounds etc.
Application of heat

The development of strength of concrete is a function of not only time but also that of temperature.
When concrete is subjected to higher temperature it accelerates the hydration process resulting in
faster development of strength.
The exposure of concrete to higher temperature is done in the following manner:
(a) Steam curing at ordinary pressure.
(b) Steam curing at high pressure.
(c) Curing by Infra-red radiation.
(d) Electrical curing.
(e)

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Module II Dept. of Civil Engineering, MEAEC
Steam curing at ordinary pressure

Steam curing at ordinary pressure is applied mostly on prefabricated elements stored in a chamber.
The chamber should be big enough to hold a day’s production. The door is closed and steam is
applied. The steam may be applied either continuously or intermittently. An accelerated hydration
takes place at this higher temperature and the concrete products attain the 28 days strength of
normal concrete in about 3 days.
High Pressure Steam Curing

In the steam curing at atmospheric pressure, the temperature of the steam is naturally below 100°C.
The steam will get converted into water, thus it can be called in a way, as hot water curing. This is
done in an open atmosphere. The high pressure steam curing is something different from ordinary
steam curing, in that the curing is carried out in a closed chamber. The superheated steam at high
pressure and high temperature is applied on the concrete. This process is also called “Autoclaving”.
The following advantages are derived from high pressure steam curing process:

(a) High pressure steam cured concrete develops in one day, or less the strength as much as the 28
days’ strength of normally cured concrete. The strength developed does not show retrogression.

(b) High pressure steam cured concrete exhibits higher resistance to sulphate attack, freezing and
thawing action and chemical action. It also shows less efflorescence.
(c) High pressure steam cured concrete exhibits lower drying shrinkage, and moisture movement.
Curing by Infra-red Radiation

Curing of concrete by Infra-red Radiation has been practiced in very cold climatic regions in Russia. It
is claimed that much more rapid gain of strength can be obtained than with steam curing and that
rapid initial temperature does not cause a decrease in the ultimate strength as in the case of steam
curing at ordinary pressure. The system is very often adopted for the curing of hollow concrete
products. The normal operative temperature is kept at about 90°C.
Electrical Curing

Another method of curing concrete, which is applicable mostly to very cold climatic regions is the use
of electricity. This method is not likely to find much application in ordinary climate owing to economic
reasons.

Concrete can be cured electrically by passing an alternating current (Electrolysis trouble will be
encountered if direct current is used) through the concrete itself between two electrodes either
buried in or applied to the surface of the concrete. Care must be taken to prevent the moisture from
going out leaving the concrete completely dry.

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Dept. of Civil Engineering, MEAEC Module II
PROPERTIES OF FRESH CONCRETE
Before placement in any mold without compaction is the fresh concrete. Or just after placing.

The performance requirements of hardened concrete are more or less well defined with respect to shape,
finish, strength, durability, shrinkage and creep. To achieve these objectives economically, the fresh
concrete, in addition to having a suitable composition in terms of quality and quantity of cement,
aggregate and admixtures, should satisfy a number of requirements from the mixing stage till it is
transported, placed in formwork and compacted. The requirements may be summarizes as follows:

a. The mix should be able to produce a homogeneous fresh concrete from the constituent
materials.
b. The mix should be stable, in that it should not segregate during transportation and placing
when it is subjected to forces during handling operations of limited nature.
c. The mix should be cohesive.
d. The mix should be amenable to proper and thorough compaction into a dense, compact
concrete with minimum voids under the existing facilities of compaction at the site.
e. The mix should be possible to attain satisfactory surface finish without honeycombing or
blowing holes from formwork and on free surface by trowelling and other processes. This
capability is termed as finishability.
PROPERTIES
1. Workability
2. Compactability
3. Mobility
4. Stability
5. Consistency
6. Segregation & bleeding
WORKABILITY

Workability of concrete can be defined as “the property of concrete that determines the amount of
useful internal work necessary to produce full compaction”.100% compaction is an important
parameter contributing to the maximum strength. Lack of compaction will result in air voids which
has damaging effect on strength and durability.

Workable concrete is one which exhibits very little internal friction between particles or which
overcomes the frictional resistance offered by formwork surface or reinforcement contained in the
concrete. Workability of concrete can be also defined as the ease with which the concrete is mixed,
handled, transported, placed and compacted.

Consistency is a general term to indicate the degree of fluidity or the degree of mobility. A concrete having
high consistency need not be of right workability for a particular job. So workability can be considered as
job specific. Workability differs for mass concrete, for roof slab, for thick section, for thin section, for
heavily reinforced for roller compacted and for vibrated one. In general, workability differs for the type of
work, the thickness of section, extent of reinforcement and method of compaction.
Factors affecting workability
1. Water content
2. Mix proportions
3. Size of aggregates
4. Shape of aggregates
5. Surface texture of aggregates
6. Grading of aggregates
7. Use of admixtures

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1. Water content: If the water content is more the fluidity of concrete will be more and hence
workability will be more. When the water content is increased the strength will be decreased. So
to improve workability only as a last recourse the addition of more water is to be resorted to.
More water can be added provided correspondingly higher quantity of cement is also added to
keep the water cement ratio a constant.

2. Mix proportions: The higher the aggregate cement ratio the leaner will be the concrete. In rich
mix with lower aggregate cement ratio more paste is available to make the mix cohesive and
fatty to give more workability. In lean concrete less quantity of paste is available for lubrication.
For low aggregate cement ratio the workability will thus be more.

3. Aggregate size: For a given quantity of water and paste larger size of aggregate will give higher
workability within certain limits. The bigger the size of aggregates lesser will be the total surface area
in a given volume and hence less quantity of water is required for wetting the surface. So for bigger
size aggregates less paste is sufficient for lubricating the surface to reduce internal friction. For a
given quantity of water and paste bigger size of aggregates will give higher workability.

4. Aggregate shape: Angular, elongated or flaky aggregates make the concrete very harsh when
compared to rounded aggregates. For rounded aggregates there is reduced frictional resistance.
Better workability is therefore rounded or cubical aggregates when compared to angular,
elongated or flaky. Also for a given volume the area of the surface will be less for rounded and
cubical aggregates in which case less paste is sufficient for lubricating the surface to reduce
internal friction.

5. Surface texture: Rough textured aggregates will show poor workability when compared to
smooth textured. Reduction of inter particle frictional resistance offered by smooth aggregates
also contributes to higher workability.

6. Grading of aggregates: A well graded aggregate is one which has least amount of voids in a
given volume. Other factors being constant, when the total voids are less, excess paste is
available for lubrication and least amount of efforts is required for compaction. Hence it gives
better workability.

7. Use of admixtures: An admixture reduces the internal friction between the particles and
improves workability. The plasticizers and super plasticizers greatly improve the workability. Use
of air entraining agents, fine glassy pozzolanic materials also improves workability.

8. Entrapped air: For normal concrete without air entrainment, for the same workability, the
water content decreases with increase in maximum size of aggregates. When air is entrained,
the water content can be reduced in accordance with the relation shown below.

Symbol Air entrained %

a 12
b 10
c 8
d 6
e 4
f 2

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Measurements of workability:
The tests commonly employed to measure workability are
a. Slump test d. Vee Bee consistometer test
b. Compaction factor test e. Kelly Ball test
c. Flow test f. Remoulding test
b. Slump test

The term slump simply refers to the consistency of the concrete in a plastic state. The vertical
settlement mm in the test is the slump. Slump test is used as a control test and gives an indication of
the uniformity concrete from batch to batch. The manner in which concrete slumps also gives
additional information on workability and quality of concrete

• The apparatus consist of a metallic mould in the form of a frustum of a cone with 20 cm bottom
diameter, 10 cm top diameter and a height of 30cm.
• For tamping the concrete a tamping rod 60 cm long, 16 mm dia and with a bullet end is used.
• The mould is filled with the fresh concrete in four layers each layer compacted with 25 nos.
tamping by the rod.
• After the top layer is rodded the concrete is struck off with trowel
• The mould is removed slowly in the vertical direction. This allows the concrete to subside.
• The vertical settlement in mm is the slump

The true slump, shear slump and collapse are the pattern of slumps. If the concrete slumps evenly it
is true slump, if one part of slump slides down it is shear slump. Collapse slump is obtained with lean
harsh or very wet mixes.

Slump test is not sensitive for a stiff mix. The slump test is useful on site to check day to day or batch
to batch variation in the quantity of mix. The simplicity of the test has made it popular. An increase in
slump may mean that there is an increase in water content or there is a change in gradation of
aggregates. Usually a slump of 25-75 is treated as low, 50 to 100 as medium, and 100 to 150 as high.
When deciding the ideal slump we have to keep in mind that slump depends on the wetness of the
sample, properties of the ingredients, temperature etc.

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Module II Dept. of Civil Engineering, MEAEC

Degree of Slump Compacting

Placing conditions Slump mm
workability in. factor

Blinding concrete;
Shallow sections; Very low 0-25 0-1 0.78
Pavement using pavers

Mass concrete;
Lightly reinforced sections in slabs,
beams, walls, columns; low 25-50 1-2 0.85
Floors; hand placed pavements; canal
lining; strip footings
Heavily reinforced sections in slabs,
25-100
beams, walls, columns; slipform work; medium 0.92
2-4
pumped concrete
0.95
Trench fill; in situ filling High 100-175 4-7

Tremie concrete Very high Too large to measure

c. Compaction factor test

The test is carried out to determine the workability of fresh concrete as per IS1119-1959 by using a
compacting factor apparatus

Compaction factor apparatus

• Fresh concrete is placed in the upper hopper A (top internal dia 25.4 cm, bottom internal dia 12.7
cm and internal height 27.9 cm
• The trap door of top hopper is opened and allowed to fall in to the lower hopper B. The lower
hopper is with top ID 12.7 cm and internal height 22.9cm. Total distance between bottom of A
and top of B is 20.3 cm.
• The trap door of hopper B is opened and concrete is allowed fall in to the cylinder C.
• The concrete collected in the cylinder is leveled at the top level and weighed. The weight is that
of partially compacted concrete.

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Dept. of Civil Engineering, MEAEC Module II
• The cylinder is then emptied and refilled with concrete in 5 cm layers and compacted fully
preferably by vibrating. The weight is considered as the weight of fully compacted concrete.

The ratio of the density achieved in the test to density of same concrete fully compacted gives the
compacting factor.

Compacting factor test measures the inherent characteristics of the concrete which relates very close
to the workability requirements of concrete and as such it is one of the good tests to depict the
workability of concrete.
d. Flow test

Flow test gives an indication of the quantity of concrete with respect to consistency, cohesiveness
and the proneness to segregation. In this test, a standard mass of concrete is subjected jolting. The
spread or the flow of the concrete is measured and this flow is related to workability.

• A mould made from smooth metal casting in the form of a frustum of a cone with base dia. 25
cm, top dia. 17 cm and height 12 cm is kept on the centre of a table 76 cm in dia. Over which
concentric circles are marked.
• Concrete is filled in the mould in two layers each rodded 25 times with a tamping rod 1.6 cm
dia and 61 cm long. The excess of concrete which has overflowed the mould is removed.
• The mould is lifted vertically upward and the table is then raised and dropped 12.5 mm 15
times in about 15 seconds
• The diameter of the spread concrete is measured in about 6 directions and the average spread
is noted. The flow of concrete is the percentage increase in the average diameter of the spread
over the base diameter of the mould.
Flow percent = {(spread diameter in cm-25)/25} x 100
The value could vary from 0-150 %.

e. Kelly ball test

This is simple field test and it consists of measuring the

indentation made by 15 cm diameter metal hemisphere
weighing 13.6 kg. When freely placed on fresh concrete. The
test has been devised by Kelly .For this test the minimum
depth of concrete must be at last 20 cm and the minimum
distance from the centre of the ball to nearest edge of the
concrete 23 cm. So it cannot be used in thin section. The
depth of penetration gives a measure of workability.
f. Vee Bee Consistometer Test

This laboratory test measures indirectly the workability of concrete. It is suitable for stiff concrete
mixes having low and very low workability. The test consists of a vibrating table, a meet pot, a sheet
metal cone and a standard iron rod.

• Slump test is performed placing the slump cone inside the sheet metal cylindrical pot of the
consistometer
• The glass disc attached to the swivel arm is turned and placed on the top of the concrete in the
pot
• The electric vibrator is switched on and simultaneously a stop watch started
• The vibration is continued till the conical shape of the concrete disappears and it assumes a
cylindrical shape the time of which is noted
• The consistency of concrete should be expressed in Vee Bee degrees which is equal to the time
in seconds recorded above
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g. Remoulding test:

• The remoulding test was developed by Powers.

• A standard slump cone is placed inside a cylinder of diameter 305 mm and height 203 mm.
• The cylinder is mounted rigidly on flow table described earlier, adjusted give 6.3 mm drop.
• There is a 210 mm diameter, 127 mm high inner ring inside the main cylinder. The distance
between the bottom of the ring and the bottom of the cone can be adjusted to 67 mm or
76 mm.
• The slump cone is filled as per the standards. It is then removed and a disc-shaped rider
weighing 1.9 kg placed on the top.
• The table is now jolted at the rate of one jolt per second until the bottom of the rider is 81 mm
above the base plate.
• At this point it can be observed that the shape of the concrete has changed from that of
frustum of a cone to that of a cylinder.
• The effort required to remould a cone in to cylinder is expressed in terms of the no of jolts

The remoulding test is a valuable laboratory test, especially for assessing the remoulding
characteristics of the mix, which are directly related to workability.
COMPACTABILITY

Compactability is the ease with which concrete can be compacted. Or it is the amount of internal work
required to produce complete compaction. This property of the mix depends upon many factors such as
the amount, fitness, and chemical composition of cement, the amount of water, the grading and shape of
fine aggregates, and the presence or absence of entrained air and admixtures. The addition of certain
admixtures and entrained air greatly increases Compactability without increasing the slump.
MOBILITY

Mobility is the ease with which concrete can flow in to the form work around steel, forming adequate
bonds, i.e., the ability to be moulded. This measure depends up on the type of form work, the
arrangement of steel in the mould, the method adopted in moulding, the time lag between the
mixing and pouring, and the nature of work.

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STABILITY

The ability of a concrete to remain q stable, homogeneous, coherent mass without segregation both
during handling (static stability) and during vibrations (dynamic stability) is termed stability.
CONSISTENCY

Consistency refers to the firmness of concrete or the ease with which it flows. In turn it refers to the
mean degree of wetness, as wet concrete can flow better. Consistency is an indication of workability.
It shows the relative mobility, or the ability of wet, fresh concrete to flow. A wet mix can flow better
compared to a dry mix. Similarly, a soft mix is more mouldable compared to a stiff mix

Consistency Slump-Mm Percentage Flow Typical Structures

Dry 0-2.5 0-20 Dams, large piers
Stiff 12.5-72.5 15-60 Foundations, small piers

Medium 50-137.5 50-100 Footings

Large structure members,
Wet 137.5-200 90-120
beams, slabs
Small structure members, thin
sloppy 175-250 110-150
slabs, small members

SEGREGATION

It is defined as the separation of constituent materials of concrete. A good concrete is one in which
all the ingredients are properly distributed to make a homogeneous mixture. Segregation may be of
three types.
1. The course of aggregate separating out or settling down from the rest of the matrix
2. The paste or matrix separating away from course of aggregates
3. Water separating out from the rest of material being a material of lowest specific gravity.
Segregation is often seen occurring
• Due to improper proportioning of ingredients and improper mixing
• When concrete is dropped from heights
• When concrete is discharged from badly designed mixer with worn out blades.
• Conveyance of concrete by conveyor belts, wheel barrows, long distant hauls by dumper etc.
• Excess vibration of too wet concrete
• Working too much with trowel, float or rammer
Segregation can be minimized by
• Restricting quantity of water
• Careful handling, transporting placing and compacting
• Adding air entraining admixture during mixing
• Restricting the height of pour
BLEEDING

The water gain in concrete structures is referred as Bleeding. The process of rise of water along with
cement particles to the surface of freshly laid concrete is known as bleeding. The particles of fine
sand and cement are carried by the rising water to the surface forming a scum layer on hardening.
This happens when there is excessive quantity of water on the mix or when there is excessive
compaction. Bleeding is a particular type of segregation.
Bleeding can be reduced

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Module II Dept. of Civil Engineering, MEAEC
• By proper proportioning
• Use of finely divided pozzolanic materials reduces the bleeding by creating a longer path
• Use of air entraining agents
• Use of fine cement with low alkali content
• Rich concrete mixes are less susceptible to bleeding than lean mixes.
Laitance:
Sometimes during bleeding along with water certain quantity of cement comes up and accumulates at the
surface. This formation of cement paste at the surface is called Laitance. Formation of laitance decreases
the wearing quality of slab and pavement surfaces. The laitance formed produces dust in summer and
mud in winter. So while concreting the laitance shall be removed before next lift is poured.

Test for Bleeding of concrete:

The test consists of determination of relative quantity of mixing water that will bleed from a sample
of freshly mixed concrete.

• A cylindrical container of approximately 0.01 m3 capacity having an inside diameter of 250

mm and inside height of 280 mm is used.
• For tamping the concrete a tamping rod 60 cm long, 16 cm dia and with bullet end is used
• A pipette for drawing of free water from the surface and a graduated jar of 100 ml capacity
for measuring quantity of water are needed for the test.
• Fresh concrete is filled in 50 mm layers for a depth of 250 mm
• The test specimen is weighed and knowing the water content for 1m3 of concrete quantity
of water in the cylindrical container is found
• Cover the container with a lid. Water accumulated at the top is drawn by means of a
pipette at ten minutes interval for the first 40 minutes and their after at 30 minutes
intervals till the bleeding ceases. Weigh this water

PROPERTIES OF HARDENED CONCRETE

Hardened concrete is the concrete that is in a solid state and has developed certain strength.
Reaction continues with time and produced hard, strong and durable solid material
Properties of Hardened Concrete:
1. Strength of concrete
2. Elastic properties of concrete
3. Creep
4. Shrinkage
5. Thermal properties
6. Fatigue

STRENGTH OF CONCRETE:
Strength of concrete is commonly considered as its most valuable property, although in many
practical cases, other characteristics such as durability and permeability may be more important.
Strength usually gives an overall picture of the quality of concrete because strength is directly related
to the structure of the hydrated cement paste. Strength of concrete could be defined as the ultimate
2
load that causes failure (or is its resistance to rupture) and its units are N/mm or MPa.
Fracture and failure of Concrete

Concrete specimens subjected to any state of stress can support loads up to 40-60% of ultimate load
without any apparent signs of distress. As the load is increased above this level, soft but distinct
noises of internal disruption can be heard until, at about 70-90% of ultimate load, small fissures or
cracks appear on the surface. At ultimate load and beyond, the specimens are increasingly disrupted
and eventually fractured into a large number of separate pieces

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Dept. of Civil Engineering, MEAEC Module II
Types of Concrete Strength
(a) Compressive strength

The concrete is primarily used to exploit its compressive stresses. The compressive strength of
concrete is defined as the strength of 28 days old specimens tested under uniaxial compressive load.
Cubes, cylinders and prisms are the three types of compression test specimens used to determine the
compressive strength on testing machines. The cubes are usually of 100 mm or 150 mm side, the
cylinders are 150 mm diameter by 300 mm height. The specimens are cast, cured and tested as per
standards prescribed for such tests. When cylinders are used, they have to be suitably capped before
the test, an operation which is not required when other types of specimen are tested. The
compressive strengths given by different specimens for the same concrete mix are different. The
cylinders and prisms of a ratio of height or length to the lateral dimension give strength of about 75-
85 % of cube strength of normal strength of concrete. The effect of height/lateral dimension ratio of
specimen on compressive strength is given in fig. below
(fc) cylinder = (0.85-0.80)(fc) cube

Comparison between Cube and Cylinder Strength

It is difficult to say whether cube test gives more realistic strength properties of concrete or cylinder gives
a better picture about the strength of concrete. However, it can be said that the cylinder is less affected by
the end restrains caused by platens and hence it seems to give more uniform results than cube. Therefore,
the use of cylinder is becoming more popular, particularly in the research laboratories.

Cylinders are cast and tested in the same position, whereas cubes are cast in one direction and tested
from the other direction. In actual structures in the field, the casting and loading is similar to that of
the cylinder and not like the cube. As such, cylinder simulates the condition of the actual structural
member in the field in respect of direction of load.

The points in favor of the cube specimen are that the shape of the cube resembles the shape of the
structural members often met with on the ground. The cube does not require capping, whereas
cylinder requires capping. The capping material used in case cylinder may influence to some extent
the strength of the cylinder.

(b) Tensile strength

The tensile strength of concrete is much lower than the compressive strength, largely because of the
ease with which crack can propagate under tensile loads. The tensile strength of concrete is
measured in three ways: Direct tension, Splitting tension (Indirect method) and flexural tension.

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Module II Dept. of Civil Engineering, MEAEC

The methods used to determine the tensile strength of concrete can be broadly classified as direct
and indirect method. The direct methods suffer from a number of difficulties related to holding the
specimen properly in the testing machine without introducing stress concentration and to the
application of uniaxial tensile load which is free from eccentricity to the specimen. Even a very small
eccentricity of load will induce bending and axial force conditions and the concrete fails at apparent
tensile stress other than tensile strength. Because of the difficulties involved in conducting the direct
tension test, a number of indirect methods have been developed to determine the tensile strength.
In these tests, in general a compressive force is applied to a concrete specimen in such a way that
specimen fails due to tensile stresses induced in the specimen. The tensile stress at which failure
occurred is the tensile strength of concrete.
(c) Flexural strength

Concrete as we know is relatively strong in compression and weak in tension. In reinforced concrete
members, little dependence is placed on the tensile strength of concrete since steel reinforcing bars
are provided to resist all tensile forces. However, tensile stresses are likely to develop in concrete due
to drying shrinkage, rusting of steel reinforcement, temperature gradients and many other reasons.
Therefore, the knowledge of tensile strength of concrete is of importance.

The determination of flexural tensile strength is essential to estimate the load at which the concrete
members may crack. As it is difficult to determine the tensile strength of concrete by conducting a
direct tension test, it is computed by flexure testing. The flexure tensile strength at failure or the
modulus of rupture is thus determined and used when necessary. Its knowledge is useful in the
design of pavement slabs and airfield runway as flexural tension is critical in these cases. The
modulus of rupture is determined by testing standard test specimens of 150mm X 150mm X 700 mm
over a span of 600 mm or 100 mm X 100mm X 500 mm over a span of 400 mm, under symmetrical
two-point loading.

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Dept. of Civil Engineering, MEAEC Module II

The flexural strength of the specimen is expressed as the modulus of rupture fb which if ‘a’ equals the
distance between the line of fracture and the nearer support, measured on the center line of the
tensile side of the specimen, in cm, is calculated to the nearest 0.05 MPa as follows:

When ‘a’ is greater than 20.0 cm for 15.0 cm specimen or greater than 13.3 cm for a 10.0 cm
specimen, or
=

Or

when ‘a’ is less than 20.0 cm but greater than 17.0 cm for 15.0 specimen, or less than 13.3

cm but greater than 11.0 cm for a 10.0 cm specimen

3
=

Where,
b = measured width in cm of the specimen,
d = measured depth in cm of the specimen at the point of failure,
l = length in cm of the span on which the specimen was supported, and
p = maximum load in kg applied to the specimen

If ‘a’ is less than 17.0 cm for a 15.0 cm specimen, or less than 11.0 cm for a 10.0 cm specimen, the
results of the test be discarded.

The results are affected by the size of the specimens; casting, and moisture conditions; manner of
loading; rate of loading, etc.

Relation between Compressive strength and tensile strength

It is seen that strength of concrete in compression and tension (both direct tension and flexural
tension) are closely related, but the relationship is not of the type of direct proportionality. The ration
of the two strengths depends on general level of strength of concrete. In other words, for higher
compressive strength concrete shows higher tensile strength, but the rate of increase of tensile
strength is of decreasing order.

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Module II Dept. of Civil Engineering, MEAEC
Tensile strength of concrete is proportional to the square root of the compressive strength. The
proportionality constant depends on many factors, such as the concrete strength and the test
method used to determine the tensile strength

The following relations can be used as a rule of thumb:

Direct tensile strength, = 0.35√

Split tensile strength, = 0.50√

Flexural tensile strength, = 0.64√

2
Where fc is compressive strength in N/mm

Relationship between Compressive Strength, Tensile Strength and Flexural Strength

STATISTICAL QUALITY CONTROL OF CONCRETE

Concrete like most other construction processes, have certain amount of variability both in materials
as well as in constructional methods. This results in variation of strength from batch to batch and also
within the batch. It becomes very difficult to assess the strength of the final product.
It is not possible to have a large number of destructive tests for evaluating the strength of the end
products and as such we have to resort to sample tests. It will be very costly to have very rigid criteria
to reject the structure on the basis of a single or a few standard samples.
The basis of acceptance of a sample is that a reasonable control of concrete work can be provided, by
ensuring that the probability of test result falling below the design strength is not more than a
specified tolerance level.
The aim of quality control is to limit the variability as much as practicable. Statistical quality control
method provides a scientific approach to the concrete designer to understand the realistic variability
of the materials so as to lay down design specifications with proper tolerance to cater for
unavoidable variations. The acceptance criteria are based on statistical evaluation of the test result of
samples taken at random during execution. By devising a proper sampling plan it is possible to ensure
a certain quality at a specified risk.
The compressive strength test cubes from random sampling of a mix, exhibit variations, which are
inherent in the various operations involved in the making and testing of concrete. If a number of cube
test results are plotted on histogram, the results are found so follow a bell shaped curve known as
“Normal Distribution Curve”. The results are said to follow a normal distribution curve if they are
equally spaced about the mean value and if the largest number of the cubes have a strength closer to
the mean value, and very few number of results with much greater or less value than the mean value.
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Dept. of Civil Engineering, MEAEC Module II
However, some divergence from the smooth curve can be expected, particularly if the number of
results available is relatively small

Common Terminologies
The common terminologies that are used in the statistical quality control of concrete are explained
below.
(a) Mean strength:

This is the average strength obtained by dividing the sum of strength of all the cubes by the number
of cubes. ∑
=

Where, = mean strength

∑ = sum of the strength of cubes N = number of cubes.

(b) Variance:

This is the measure of variability or difference between any single observed data from the mean
strength.
(c) Standard Deviation:
This is the root mean square deviation of all the results. This is denoted by S.

∑( − )2
= √
−1

Where S = Standard deviation

n = number of observations
= particular value of observations

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Module II Dept. of Civil Engineering, MEAEC
= arithmetic mean

Standard deviation increases with increasing variability. It may be noted that the value of S is
minimum for very good control and progressively increases as level of control deceases. The spread
of the curve along the horizontal scale is governed by the standard deviation, while the position of
the curve along the vertical scale is fixed by the mean value.
(d) Coefficient of variation

It is an alternative method of expressing the variation of results. It is a non-dimensional measure of

variation obtained by dividing the standard deviation by the arithmetic mean and is expressed as:
= ×100

With constant coefficient of variation, the standard deviation increases with strength and is larger for
high strength concrete.

Application
The standard deviation and the coefficient of variation are useful in the design and quality control of
the concrete. As the strength test results follow normal distribution, there is always may fall below
the specified strength. Considering this fact IS 456-2000 has brought in the concept of characteristic
compressive strength.
In the design of concrete mixes, the target mean strength should be appreciably higher than the
minimum or characteristic strength if the quality of concrete is to comply with the requirements of
specifications. The expected variation in compressive strength is represented by a standard deviation
or coefficient of variation. From these it is possible to determine the target mean strength of the mix.
The target mean strength ft is obtained by using the following relation,
= +
= + 1.65

Where,
fck = Characteristic compressive strength after 28days
= tolerance factor or probability factor = 1.65 where not more than 1 in 20 (5%) of test
results are expected to fail
S = Standard deviation
If coefficient of variation is used,
=
1− 100

Where, v = Coefficient of variation

However, the use of the coefficient of variation is not envisaged in IS 456-2000

ACCEPTANCE CRITERIA
Compressive strength

The acceptance criteria given in IS 456 -2000 stipulates that the strength requirement is satisfied
when conditions given in following table is met,

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 Dept. of Civil Engineering, MEAEC Module II

Flexural strength
When both the following conditions are met, the concrete complies with the specified flexural
strength.
a. The mean strength determined from any group of four consecutive test results exceeds the
2
specified characteristic strength by at least 0.3 N/mm
b. The strength determined from any test result is not less than the specified characteristic
2
strength less 0.3 N/mm
DATA REQUIRED FOR MIX PROPORTIONING BASED ON IS 10262-2009:

  Grade designation
  Type of cement
  Maximum nominal size of aggregate( MNSA)
  Minimum cement content
  Max. water cement ratio
  Workability
  Exposure conditions
  Max temperature of concrete at the time of placing
  Method of transporting and placing
  Early age strength requirement if required
  Type of aggregate
  Max. cement content
 Whether admixture is used or not and the type of admixture.
MIX DESIGN METHODS
1. BIS method
2. ACI method
3. Arbitrary proportion.
4. Fineness method.
5. DOE method (British standard mix design developed by Department of Environment in 1975)
BIS METHOD

The Bureau of Indian Standards recommended a set of procedure for design of concrete mix (IS
10262-2009). This method can be applied for both medium and high strength concrete.
Procedure
1. Collection of data

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Module II Dept. of Civil Engineering, MEAEC
The data required for mix proportioning such as Concrete grade, type of cement, Aggregates,
maximum size of aggregates, properties of cement & aggregates etc. shall be collected

1. Determine the mean target strength ft from the specified characteristic compressive strength at 28-
day fck and the level of quality control ‘S’.
ft = fck + t S
ft = fck + 1.65 S,
where S is the standard deviation
fck = Characteristic compressive strength after 28days
t = tolerance factor
S = Standard deviation obtained from table 39 Of SP23
Standard deviation
Table (Assumed Standard Deviation as Per IS 456 Of 2000)
Grade of Assumed standard deviation
2
concrete (N/mm )
M10
3.5
M15
M20
4.0
M25
M30
M35
M40 5.0
M45
M50

Table: Values of tolerance factor‘t’ (IS: 10262-1982)

Accepted proportion t
of low results
1 in 5 0.84
1 in 10 1.28
1 in 15 1.50
1 in 20 1.65
1 in 40 1.96
1 in 100 1.33

2. Selection of water Cement Ratio:

Obtain the free water cement ratio corresponding to the targeted mean strength from fig. 46
page 119 of SP23 (figure below) . The water cement ratio so chosen is checked against the limiting
water cement ratio for the requirements of durability given in table 5 page 20 of IS 456 and adopt the
lower of the two values.

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Dept. of Civil Engineering, MEAEC Module II

3. Estimation of entrapped air:

Estimate the amount of entrapped air for maximum nominal size of the aggregate is selected from
the table 41 page 113 of SP23.

4. Select the water content:

Select the water content for the required workability and maximum size of aggregates (for
aggregates in saturated surface dry condition) from table 42 & 43 of SP23

5. Determine the percentage of fine aggregate in total aggregate by absolute volume from table for
the concrete using crushed coarse aggregate.

7. Adjust the values of water content and percentage of sand as provided in the table for any
difference in workability, water cement ratio, grading of fine aggregate and for rounded aggregate
the values are given in table 44.

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Module II Dept. of Civil Engineering, MEAEC

8. Determination of Cement Content:

Calculate the cement content from the water-cement ratio and the final water content as
arrived after adjustment (cement by mass = water content/water cement ratio). Check the cement
against the minimum cement content from the requirements of the durability from IS 456, and
greater of the two values is adopted.
9. Determination of Coarse and Fine aggregate:

From the quantities of water and cement per unit volume of concrete and the percentage
of sand already determined in steps 6 and 7 above, calculate the content of coarse and fine
aggregates per unit volume of concrete from the following relations:

Where,
3
V = absolute volume of concrete = gross volume (1m ) minus the volume of entrapped
air Sc = specific gravity of cement
W = Mass of water per cubic meter of concrete, kg
C = mass of cement per cubic meter of concrete, kg
P = ratio of fine aggregate to total aggregate by absolute volume
fa, Ca = total masses of fine and coarse aggregates, per cubic meter of concrete, respectively in kg,
Sfa, Sca = specific gravities of saturated surface dry fine and coarse aggregates, respectively

10. Determine the concrete mix proportions for the first trial mix.

11. Prepare the concrete using the calculated proportions and cast three cubes of 150 mm size and
test them wet after 28-days moist curing and check for the strength.
12. Prepare trial mixes with suitable adjustments till the final mix proportions are arrived at.

*******************************
Prepared By

NAJEEB. M
Assistant Professor
Dept. of Civil Engineering
MEA Engineering College

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MODULE 3
 Dept. of Civil Engineering, MEAEC Module III
MODULE 3
Syllabus:
Building construction - Preliminary considerations for shallow and deep foundations
Masonry – Types of stone masonry – composite walls - cavity walls and partition walls -Construction
details and features – scaffoldings
Introduction to Cost-effective construction - principles of filler slab and rat-trap bond masonry.

BUILDING CONSTRUCTION
Primary considerations
 Before starting a new construction project, check whether the area comes in an Earth Quake
prone zone. While doing construction work safety measures should be taken for earth quake
 protection.
 The whole area of the building should be constructed at one time to avoid settlement in any
portion of the building. If the construction is done in small portions, there may be chances of
 the settlement in foundation.
 Keep in mind the norms/rules of concerned area about building construction.
  Know about the authorities whose sanction is required to start the construction work.
 Know how much time it will take for getting the sanction.
 Search for a qualified architect or designer.
 Prepare the plan according to the area of the plot.
  Arrange structural drawing according to the type of soil.
 Know availability of the building materials, their quality and reputed material suppliers.
 See the availability of good quality of water and availability of electric connection.
 Access the labor/contractor for construction.
 Have knowledge about high flood level and the level of surrounding buildings and roads

 The site should be cleared if roots of the tree exists they should be removed up to 2 feet (60
 cm.) below the ground level.
 Excavation for foundation should be done according to the designs and exact width and depth
of the wall should be dug. If extra depth is made due to any reasons or any soft places found,
 those should be filled in with coarse sand or concrete.
 In case the water comes in trenches, it should be pumped out immediately.
Preliminary works to do before starting construction
Cleaning: Remove jungle from plot area. If there is any tree in the buildup area, un-rooted them
completely. And remove from the plot area.
Levelling: Thoroughly level the ground. If there is any hole in the ground fill up that properly. Remove
excess soil from the plot or fill up the plot by imported soil to take the ground to desired level, if
required.
Fencing: Now plot area is cleaned and levelled. It is time to secure the plot area. It can be done by
making permanent boundary wall or temporary fencing around plot. Temporary fencing is the more
common way. Builder logo or company logo can be setup with fencing for branding. Also, safety
signboard can be attached with fence.
Site office: Site office can be temporary or fixed depending on situation. If there is any driver's
waiting room or visitor's waiting room or guest waiting room to build later then build that first to use
as site office. But that is exceptional. The common practice in this case is temporary site office. . You
should make a toilet which is separated from labor’s toilet as you will have many yip clients and
visitors during construction period.
Store: The most essential thing in any construction site is store. To keep safe various building materials
from un-wanted damage or stolen, make a store before starting construction. Make, a separate store

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Module III Dept. of Civil Engineering, MEAEC
for cement because that are huge quantities and that are quickly affected by' weathering impact. So
the cement store should be protected from weather effect, especially from water.
Labour shed: It is common practice that, workers, who work in the construction project stay at site.
For them a shed should be made at site with essential facilities like water and power supply and
sanitation. Some construction companies have permanent labour accommodation, so they don't
need to make shed at site.
Utility connection: As civil construction needs continuous power and water supply, so ensure them
first. For water supply, you can connect to city's water supply line, or you can install a deep tube well.
For electricity connection, connect to city's power supply line for you can keep a generator at site.
Components of Building
There are two basic components of a building.
1. Sub Structure: The part of building that is constructed below ground level.
2. Super Structure: The part of building that is above ground level.
Sub-Structure
Footing and plinth of a building are a part of a sub-structure. This part of building safely transfers the
load of building to the underlying soil. Therefore, footing should be of such strength that it can easily
carry the building load. Failure of footing leads to failure of building. Width and depth of footing
should be designed according to the load of a building coming on it plus the bearing capacity of soil.
Bottom part of footing is generally constructed of Plain Cement Concrete (P.C.C) or Reinforced
Cement Concrete (R.C.C). Steps arc made above (P.C.C) by using bricks, stones or concrete to reach
the plinth level. Generally, Damp Proof Course (D.P.C) is laid on plinth level. This layer stops the
penetration of moisture to the super structure part of a building.
Superstructure
Super-structure is a part of structure that is above plinth level (P.L). Generally columns and walls are
constructed in super structure. Following are the important parts of super-structure.
(a) Floor
(b) Roof
(c) Lintel
(d) Parapet
(e) Sun Shade
(f) Drip Course
(g) Doors & Windows
Foundation
Foundation is the lowest artificially prepared part of the structure which transfer the load of the
super structure along with live load wind pressure earthquake loads etc. to the soil.
Foundation of a structure is always constructed below the ground level so as to increase the lateral
stability of the structure. It includes the portion of the structure below the ground level and is built, so as
to provide a firm and level surface for transmitting the load of the structure on a large area of the soil
lying underneath. The solid ground on which the foundation rests is called the Foundation Bed.
Purposes of foundations
Foundations are used for the following purposes.
1. Even distribution of load: To distribute the load of the structure over a large bearing area so as
to bring intensity of loading within the safe bearing capacity of the soil lying underneath.
2. Reduction of differential settlement: To load the bearing surface at a uniform rate so as to
prevent unequal settlement.
3. It provides stability against undermining
4. Provides safety against sliding and overturning.
5. To prevent the lateral movement of the supporting material.
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 Dept. of Civil Engineering, MEAEC Module III
6. To secure a level and firm bed for building operations.
7. To increase the stability of the structure as a whole.
8. To prevent excessive settlement of the structure.
9. To prevent or minimize cracks in the superstructure due to expansion or contraction of subsoil
because of the movement of moisture in weak soils.
Bearing capacity of soil
 The ability of the soil to support the super imposed load without excessive settlement or failure is
 called Bearing capacity of soil.
 The gross pressure intensity at which the soil fails is called Ultimate bearing capacity.

 Safe bearing capacity is the maximum pressure which the soil can carry without the risk of shear
 failure.
 Safe bearing capacity = ultimate bearing capacity/factor of safety

 Safe bearing capacity is used for the design of foundation and up to this load there is no
settlement for the soil.
Ultimate Bearing Capacity of Soils:
The intensity of loading, at the base of foundation, at which soil support fails in shear is called
ultimate bearing capacity of soils.
Safe Bearing Capacity of Soils:
The maximum' intensity of loading that the soil will safely carry without risk of shear failure is called
safe bearing capacity of soil. This .is obtained by dividing the ultimate bearing capacity by a certain
factor of safety, and it is the value which is used in the design of foundation. The factor of safety
normally; varies from 2 to 3.
Foundation selection considerations to be evaluated include:
 Ability of the foundation type to meet performance requirements (e.g., deformation, bearing
resistance, uplift resistance, lateral resistance/ deformation) for all limit states, given the soil or
 rock conditions encountered.
 Constructability of the foundation type.

 Impact of the foundation installation (in terms of time and space required) on traffic and right-
 of-way.
 Environmental impact of the foundation construction.

 Constraints that may impact the foundation installation (e.g., overhead clearance, access, and
 utilities).
 Impact of the foundation on the performance of adjacent foundations, structures, or utilities,
considering both the design of the adjacent foundations, structures, or utilities, and the
 performance impact the installation of the new foundation will have on these adjacent facilities.
 Cost of the foundation, considering all of the issues listed above
Shallow Footing Design Considerations
The following design considerations apply to shallow foundations:

  Scour must not result in the loss of bearing or stability.

 Frost must not cause unacceptable movements.
 External or surcharge loads must be adequately supported.
 Deformation (settlement) and angular distortion must be within tolerable limits.
  Bearing resistance must be sufficient.
 Eccentricity requirements must be satisfied.
 Sliding resistance must be satisfied.
 Overall (global) stability must be satisfied.
  Uplift resistance must be sufficient.
 The effects of ground water must be mitigated and/or considered in the design.

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Module III Dept. of Civil Engineering, MEAEC
Types of Foundation
Foundations are broadly classified into two categories.
 Shallow Foundations
 Deep Foundations
Shallow Foundations
Shallow foundations arc constructed where soil layer at shallow depth (up to 1.5m) is able to support
the structural loads. The depths of shallow foundations are generally less than its width.
The different types of shallow foundation are:
(a) Strip footing
(b) Spread or isolated footing
(c) Combined footing Strap or cantilever footing
(d) Mat or raft Foundation.
(e) Grillage Foundations
(a) Strip Footing:
A strip footing is provided for a load-bearing wall. A strip footing is also provided for a row of columns
which are so closely spaced that their spread footings overlap or nearly touch each other. In such a
case, it is more economical to provide a strip footing than to provide a number of spread footings in
one line. A strip footing is also known as continuous footing.

(b) Spread or Isolated Footing:

A spread footing (or isolated or pad) footing is provided to support an individual column. A spread
footing is circular, square or rectangular slab of uniform thickness. Sometimes, it is stepped to spread
the load over a large area.
Spread foundations may be of the following types
 Single footing for a column
 Stepped footing for a column
 Sloped footing for a column
 Wall footing without step
 Stepped footing for wall

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(c) Combined Footing

It supports two columns as shown in figure below. It is
used when the two column are so close to each other
that their individual footings would overlap. A combined
footing is also provided when the property line is so
close to one column that a spread footing would be
eccentrically loaded when kept entirely within the
property line. By combining it with that of an interior
column, the load is evenly distributed. A combine
fooling may be rectangular or trapezoidal in plan.
Trapezoidal footing is provided when the load on one of
the column is larger than the other column.
The principle of proportioning combined footings is to
bring the, centroid of the area of the foundation in line
with the center of gravity of loads or at least as close to
as possible.

(d) Strap or Cantilever footing:

A strap (or cantilever) footing consists of two isolated footings connected with a structural strap or a
lever. The strap connects the two footings such that they behave as one unit. The strap is designed as
a rigid beam. The individual footings are so designed that their combined line of action passes
through the resultant of the total load, a strap footing is more economical than a combined footing
when the allowable soil pressure is relatively high and the distance between the columns is large.

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(e) Mat or Raft Foundations

A mat or raft foundation is a large slab supporting a number of columns and walls under the entire
structure or a large part of the structure. A mat is required when the allowable soil pressure is low or
where the columns and walls are so close that individual footings would overlap or nearly touch each
other. Mat foundations are useful in reducing the differential settlements on non-homogeneous soils
or where there is a large variation in the loads on individual columns'.

(f) Arch foundation:

Inverted arch foundations are provided in the places where the SBC of the soil is very poor .and the
load of the structure is through walls. In such cases inverted arches are constructed between the
walls. End walls should be sufficiently thick and strong to withstand the outward horizontal thrust
due to arch action. The outer walls may be provided with buttress walls to strengthen them, below
Figure shows a typical inverted arch footing.

(g) Grillage Foundation

Grillage foundation is used when heavy structural loads from columns are required to be transferred to a
soil of low bearing capacity. Grillage foundation is often found, to be lighter and more economical. This
avoids deep excavation and provides necessary area at the base to reduce the intensity of pressure within
safe bearing capacity of soil. Depending upon the material used in construction of grillage
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Dept. of Civil Engineering, MEAEC Module III
foundation can be broadly divided in the following two categories:
(i) Steel grillage foundation
(ii) Timber grillage foundation
(i) Steel grillage foundation:
Steel grillage foundation consists of steel beams also known as grillage beams which are provided in
single or double tiers. In case of double tier grillage foundation, the top tier is laid at right angles to
the bottom one. The grillage beams of each tier are held in position by 20 mm spacer bars with 25mm
diameter pipe separators.
The beams are suitably, spaced so as to provide facility for the placing and compacting of concrete
between them. A minimum clearance of 8 cm is considered most suitable. In any case, the distance
between the flanges of the beams should not be more than one and half to two times the flange
width with a maximum of 30 cm. If the beams arc spaced more distance apart, there is a danger of
the concrete filling not acting monolithically with the beams, and as such, may result in the failure of
the foundation. In order to protect the beams against corrosion, a minimum cover of 10 cm is kept on
the outer sides of the- external beams as well as above the upper flange of the top tier, Cover of
concrete under the lower beam should not be less than 15 cm.

(ii) Timber grillage:

The timber platform consists of planks usually 8 cm to 10 cm. thick, arranged in two layers, one
longitudinal and the other across the wall extending beyond the footing base by about 45 cm to 60
cm on either side. In the lowermost layers, the planks are 5 cm to 10cm thick depending upon the
loading and
Deep Foundation
The shallow foundations may not be economical or even possible when the soil bearing capacity near
the surface is too low. In those cases deep foundations are used to transfer loads to a stronger layer,
which may be located at a significant depth below the ground surface. The load is transferred
through skin friction and end bearing
In case of deep foundation the depth is equal to or greater than its width
Deep foundations may be of the following types
1. Pile foundation.
2. Pier foundation or drilled caisson foundation.
3. Well foundation or caisson
The usual strip, rectangular or square footings come under the category of deep foundations, when
the depth of the foundation as more than the width of the footing. Well foundations are generally
adopted for bridge piers etc. and not for building foundations.
1. Pile Foundations
Pile foundation is that type of deep foundation in which the loads are taken to a low level by means
of vertical members which may be of timber, concrete or steel. Pile foundation may be adopted
 
Instead of a raft foundation where no firm bearing strata exists at any reasonable depth and the
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Module III Dept. of Civil Engineering, MEAEC
loading is uneven,
 When a firm bearing strata does exist but at a depth such as to make strip or spread footing
 uneconomical, and
 When pumping of sub-soil water would be too costly or timbering to excavations too difficult to
permit the construction of normal foundations.
Piles used for building foundation may be of four types:
(a) End bearing pile
(b) Friction pile
(c) Combined end bearing and friction pile and
(d) Compaction piles
End bearing piles
End bearing piles are used to transfer load through water or soft soil to a suitable bearing stratum.
Such piles are used to carry heavy loads safely to hard strata. Multi-storied buildings are founded on
end bearing piles, so that the settlements are minimized.
These piles transfer their load on to a firm stratum located at a
considerable depth below the base of the structure :and they derive
most of their carrying capacity from the penetration resistance of the
soil at the toe of the pile .The pile behaves as an ordinary column and
should be designed as such. Even in weak soil a pile will not fail by
buckling and this effect need only be considered if part of the pile is
unsupported, i.e. if it is in either air or water. Load is transmitted to the
soil through friction or cohesion. But sometimes, the soil surrounding
the pile may adhere to the surface of the pile and causes "Negative Skin
Friction" on the pile. This, sometimes have considerable effect on the
capacity of the pile. Negative skin friction is caused by the drainage of
the groundwater and consolidation of the
soil. The founding depth of the pile is influenced by the results of the site investigation and soil test
Friction Piles
Friction piles are used to transfer loads to a depth of a friction-
load-carrying material by means of skin friction along the length of
the pile. Such piles are generally used in granular soil where the
depth of hard stratum is very great.
The total frictional resistance can be increase in the following ways:
 By increasing the diameter of the pile
 By driving the pile to a greater depth
 By making the surface of the pile rough
 By placing the piles closely
 By grouping the piles
Combined end bearing and friction pile
These piles transfer the super-imposed load both through side friction as
well as end bearing. Such piles are more common, especially when the end
bearing plies pass through granular soils.

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Compaction piles
These piles are used to compact loose granular soils, thus
increasing their bearing capacity. The- compaction piles
themselves do not carry a load. Hence they may be of weaker
material (such as timber, bamboo sticks etc.) Sometimes sand
only. The pile tube, driven to compact the soil, is gradually taken
out and sand is filled in its place thus forming a ‘sand pile'

Batter Piles
 They are inclined piles
 To resist horizontal forces
 Their stability is more against overturning

 The design of batter piles should be made by
considering the fact that they will resist most of
 the horizontal loading.
 Batter piles used together with vertical piles
assumed that part of the vertical load will be
transferred to the batter piles also

Sheet Piles
 Consists of vertical cut-off walls constructed by driving strips of steel/ precast
 concrete/aluminium/ wood into the soil
 Rarely used to furnish vertical support but are used to function as retaining wall.
 Sheet piles are used for:
  
Retain soil

 the area required for some foundation and protect it from the action of running water or
To enclose
leakage

Classification of pile with respect to type of material .

Piles are usually made of timber, concrete or steel. Timber can be used for the manufacture of
temporary piles and when the wood is available at an economical price. Concrete is used for the
manufacture pre-cast concrete piles, cast in place and pre-screened concrete piles, while steel piles
are used for permanent or temporary works
(a) Timber
(b) Concrete
(c) Steel
(d) Composite piles.

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Module III Dept. of Civil Engineering, MEAEC
Timber piles
Used from earliest record time and still used for permanent
works in regions where timber is plentiful. Timber is most
suitable for long cohesion piling and piling beneath
embankments. The timber should be in a good condition and
should not have been attacked by insects
For timber piles of length less than 14 meters, the diameter
of the tip should be greater than 150 mm. If the length is
greater than 18 meters a tip with a diameter of 125 mm is
acceptable. It is essential that the timber is driven in the right
direction and should not be driven into firm ground. As this
can easily damage the pile. Keeping the timber below the
ground water level will protect the timber against decay and
putrefaction. To protect and strengthen the tip of the pile,
timber piles can be provided with toe cover. Pressure
creosoting is the usual method of protecting timber piles.
Advantages of Wood piles
 The piles are easy to handle.
 Relatively inexpensive where timber is plentiful
 Sections can be joined together and excess length easily removed.
Disadvantages of Wood piles
 The piles will rot above the ground water level. Have a limited bearing capacity.
 Can easily be damaged during drying by stones and boulders.
 The piles are difficult to splice and are attacked by marine borers in salt water.
Concrete piles
Concrete piles can be divided to pre-cast and cast in place concrete piles:
Pre- cast concrete Piles or Pre-fabricated concrete piles
It is formed and reinforced in a high-quality controlled concrete,
usually used of square, triangle, circle or octagonal section, they are
produced in short length in one meter intervals between 3 and 13
meters. They are pre-caste so that they can be easily connected
together in order to reach to the required length. This will not
decrease the design load capacity. Reinforcement is necessary within
the pile to help withstand both handling and driving stresses. Pre
stressed concrete piles are also used and are becoming more popular
than the ordinary pre cast as less reinforcement is required.
Advantages of Pre-cast concrete Piles
 They are easy to splice. Relatively inexpensive.

 Stable in squeezing ground, for example, soft clays, silts and peats pile material can be
 inspected before piling.
 Can be driven, in long lengths.
 Can increase the relative density of a granular founding strata
Disadvantages of Pre-cast concrete piles
 Displacement, heave, and disturbance of the soil during driving.
 Can he damaged during driving. Replacement piles may be required.
 Cannot be driven with very large diameters or in condition of limited headroom.

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 Dept. of Civil Engineering, MEAEC Module III
Cast in place Concrete pile
Cast in place concrete piles are the most type commonly used for foundations due to the great
diversity available for pouring concrete and the introduction of the pile into the soil. Driving and
drilling piles are two types of cast in place concrete piles; however, the implementation of these piles
in place may be accompanied by some problems such as arching, squeezing and segregation.

Advantages of cast-in-place concrete piles

 They can be inspected before casting can easily be cut or extended to the desired length.
 Relatively inexpensive.
 The piles can be cast before excavation.
 Pile lengths are readily adjustable/

 An enlarged base can be formed which can increase the relative density of a granular
 founding stratum leading to much higher end bearing capacity
 Reinforcement is not determined by the effects of handling or driving stresses.
Disadvantages of cast-in-place concrete piles
 Heave of neighboring ground surface, which could lead to re consolidation and the
 development of negative skin friction forces on piles.
 Tensile damage to unreinforced piles or piles consisting of green concrete, where forces at
 the toe have been sufficient to resist upward movements.
 Damage piles consisting of uncased or thinly eased green concrete due to the lateral forces
set up in the soil. Concrete may be weakened if artesian flow pipes up shaft of piles when
 tube is withdrawn.
 Light steel section or Pre-cast concrete shells may be damaged or distorted by hard driving.
 Cannot be driven where headroom is limited.
  Time consuming; cannot be used immediately after the installation.
 Limited length.
Steel piles
Made of sectors in the form of H, Box or of thick pipes. They are suitable for handling and driving in
long lengths. Their relatively small cross-sectional area combined with their high strength makes
penetration easier in firm soil. They can be easily cut off or joined by welding. If the pile is driven into
a soil with low pH value, then there is a risk of corrosion, but risk of corrosion is not as great as one
might think. Tar coating or catholic protection can be .employed in permanent works.

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H Piles Box Piles Tube Pile

In case of Box piles and tube pile concrete are filled inside after driving into soil.
Advantages of Steel piles

  The piles are easy to handle and can easily be cut to desire length.
 Can be driven through dense layers. The lateral displacement of the soil during driving is low
 (steel section H or I section piles) can be relatively easily spliced or bolted.
 Can be driven hard and in very long lengths.
 Can carry heavy loads.
Disadvantages of Steel piles
 The piles will corrode,
 Will deviate relatively easy during driving.
 Are relatively expensive.
Composite piles
Combinations of different materials in one pile are used. Part of a
timber pile which is installed above ground water could be damaged
due to insect attack and decay. To avoid this, concrete or steel pile
is used above the ground water level, whilst wood pile is installed
under the ground water level.

2. Pier Foundation
 Consists of cylindrical column of large diameter to support and transfer load to firm strata below
 Difference b/w pile and pier in method of construction

3. Well foundation
 Box like structures - circular or rectangular
 Generally provided below the land or water level to desired depth
 Use for foundations of bridge pier, pump house subjected to heavy load and other structures
 Have larger dimension than pier foundation
 Hollow inside - filled with sand - plugged at bottom
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 Dept. of Civil Engineering, MEAEC Module III
 Load through perimeter wall called steining.
 Not used for buildings

MASONRY
Masonry is the art of building of structures from individual units systematically laid in horizontal
courses and bound together by mortar. Masonry is generally a highly durable form of construction.
However, the materials used, the quality of the mortar and workmanship, and the pattern in which
the units are assembled can significantly affect the durability of the overall masonry construction.
Masonry is commonly used for the building components like walls, columns and foundations, other
structures like dams, piers, retaining walls and boundary walls.
The common materials of masonry construction are bricks, hollow concrete blocks and stones. Mortar
is a homogeneous mixture produced by uniform mixing of a binding material like cement or lime with
sand and water to make a paste of required consistency. The different types of mortar used are mud
mortar, lime mortar and cement mortar. If no mortar is used, the masonry is called as dry masonry.
STONE MASONRY
Stone masonry refers to the construction of various structures
like buildings, compound walls, Retaining walls etc. using blocks
of stone joined together with mortar. The craft of stonemasonry
has existed since the dawn of civilization - creating buildings,
structures, and sculpture using stone from the earth. Famous
works of stone masonry include the Taj Mahal, Red Fort, the
Egyptian Pyramids etc.

Materials for Stone Masonry

The materials required for stone masonry are: Mortar, Stones
(a) Mortar: Mortar consists of binding material and sand in specified proportions. The binding material
may be mud, lime or cement. Generally cement - sand mortar (1: 3) is used for stone masonry.

(b) Stones: The stones to be used should be hard, durable, tough and free from any defects like
cavities, cracks etc. Common types of stones used in India are granite, sand stone, marble, laterite,
lime stone and basalt.
 Granite: It is of igneous rock, strong and durable. It is available in Kerala, Karnataka, Kashmir,
 UP, MP, Punjab, Assam etc.
 Sandstone: It is of sedimentary rock. It is easy to work and sufficiently strong. These stones
are available in almost all states of India.

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 Marble: This is of metamorphic rock. They are available in different colours and are available
 in Rajasthan and Maharashtra.
 Laterite: This is found in coastal areas of Kerala, Karnataka, Tamilnadu and West Bengal. When
freshly cut, they will be soft but in due course hardens on exposure to atmosphere. They are
 porous and as such they must be plastered with cement mortar to protect it from rain.
 Limestone: This is of calcareous rock. It is available in different colours and is easy to work. It
is available in almost all states. It easily gets disfigured in acidic atmosphere.
Classification of stone masonry
Depending on arrangement of stones in construction, degree of refinement used in shaping stone,
continuity of courses and finishing adopted, stone masonry may be broadly classified into the
following two types:
A. Rubble Masonry
i. Random rubble masonry
 Uncoursed
 Coursed
ii. Square rubble masonry
 Uncoursed
 Coursed
iii. Polygonal rubble masonry
iv. Flint rubble masonry
v. Dry rubble masonry
B. Ashlar Masonry
i. Ashlar fine
ii. Ashlar rough tooled
iii. Ashlar quarry faced
iv. Ashlar chamfered
v. Ashlar block in course
Rubble Masonry
The stone masonry in which stones as obtained from the quarry
either as undressed or roughly dressed stones are laid in a
suitable mortar is called rubble masonry. In this masonry, the
joints are wider and not of uniform thickness.
(a) Random Rubble Masonry
The rubble masonry in which either undressed stones are used
is called random rubble masonry. Further random rubble
masonry is also divided into the following two types:

Uncoursed Random Rubble Masonry

The random rubble masonry in which stones are laid without forming courses is known as uncoursed
random rubble masonry. This is the roughest and most economical type of masonry and is of varying
appearance. The stones used in this masonry are of different sizes and shapes. Before laying, all
projecting corners of stones are slightly knocked off. Vertical joints are not plumbed, joints are filled
and flushed. Large stones are used at corners and at jambs to increase their strength. The wall is
brought to a level at every 30 - 50 cm.
Suitability: Used for construction of walls of low height in case of ordinary buildings.

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Coursed Random Rubble Masonry

The random rubble masonry in which stones are laid in courses such that stones in a particular course
are of equal height is called coursed random rubble masonry. In this masonry, the stones are laid in
some what level courses. Thickness of courses vary from 30 to 45 cm. Headers of one coursed height
are placed at certain intervals. The stones are hammer dressed.
Suitability: Used for construction of residential buildings, godowns, boundary walls etc.

(b) Square Rubble Masonry

The rubble masonry in which the face stones are squared on all joints
and beds by hammer dressing or chisel dressing before their actual
laying, is called squared rubble masonry. There are two types of
squared rubble masonry.

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Un-coursed square rubble masonry:
The squared rubble masonry in which hammer dressed stones are laid without making courses is
called uncoursed square rubble masonry. It consists of stones which are squared on all joints and
beds by hammer dressing. All the stones to be laid are of different sizes.
Suitability: Used for construction of ordinary buildings in hilly areas where a good variety of stones
are economically available.

Coursed Square rubble masonry:

The square rubble masonry in which chisel dressed stones are laid in courses is called coarse square
rubble masonry. This is a superior variety of rubble masonry. It consists of stones, which are squared
on all joints and laid in courses. The stones are to be laid in courses of equal layers and the joints
should also be uniform.
Suitability: Used for construction of public buildings, hospitals, schools, markets, modern residential
buildings etc. and in hilly areas where good quality of stone is easily available.

(c) Polygonal Rubble Masonry

In this type of masonry, stones are arranged in such a manner to give a polygonal shape. The stones
are hammer dressed and are of irregular polygon shaped. These stones form irregular joints running
in all directions. More skill is required in construction.

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(d) Flint Rubble Masonry

In this type of masonry flints of varying thickness and length are used. Flints are irregularly shaped
nodules of silica. These are extremely hard but brittle. Face arrangement nay be either coursed or
uncoursed. The thickness may range from 50 mm to 75 mm and length from 150 mm to 300 mm. The
strength of flint walls may be increased by introducing lacing courses of either thin long stones or
bricks or tiles at vertical distances of one to two meters.

(e) Dry Rubble Masonry

The rubble masonry in which stones are laid without using any mortar is called dry rubble masonry or
sometimes shortly as "dry stones". It is an ordinary masonry and is recommended for constructing
walls of height not more than 6 m. In case the height is more, three adjacent courses are laid in
squared rubble masonry mortar at 3 m intervals. It is cheapest and skilled labour is required for this
type of construction. This may be used for non-load bearing walls, such as compound wall etc.

Ashlar Masonry
The stone masonry in which finely dressed stones are laid in cement or lime mortar is known as ashlar
masonry. In this masonry, the courses are of uniform height; all the joints are regular, thin and have
uniform thickness usually 3 mm. This type of masonry is much costly as it requires dressing of stones.
Suitability: This masonry is used for heavy structures, architectural buildings, high piers and
abutments of bridges.
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Module III Dept. of Civil Engineering, MEAEC
(a) Ashlar Fine
In this type of stone masonry, stone blocks of same height in each course are used. Every stone is fine
tooled on all sides. Thickness of mortar is uniform throughout and doesn’t exceed 3 mm. It is an
expensive type of stone masonry as it requires more skilled labour. Wastage of material while
dressing is also more.

(b) Ashlar Rough Tooled

In this type of ashlar masonry, the sides of the stones are rough tooled and dressed with chisels.
Thickness of joints is uniform, which does not exceed 6 mm.

(c) Ashlar Quarry Faced

This type of ashlar masonry is similar to rough tooled type except that there is chisel-drafted margin
left rough on the face which is known as quarry faced.

(d) Ashlar Chamfered

It is similar to quarry faced except that the edges are beveled
0
or chamfered to 45 for depth of 2.5 cm or more. Due to this
a groove is formed in between the adjacent blocks of stone.

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(e) Ashlar Block In Course
It is a type of ashlar masonry which is in-between rubble and ashlar. The stones are all squared and
properly dressed. It resembles to coursed rubble masonry or rough tooled ashlar masonry. Vertical
joints are not so fine a sin ashlar masonry. It is adopted in heavy works such as retaining walls,
bridges etc.
(f) Ashlar Facing
Ashlar facing is the best type of ashlar masonry. Since ashlar masonry is very expensive, it is not
commonly used throughout the whole thickness of the wall, except in works of great importance and
strength. For economy the facing is built in ashlar and the rest in rubble.

Comparison of Stone and Brick Masonry

Stone masonry Brick masonry

Art of construction where the major component Art of construction using bricks as the individual
employed is stone. units
Individual units are naturally available stones Individual units are artificially prepared bricks of
either dressed or undressed regular shape
Stronger and durable than brick masonry Less costly and suited for ordinary construction
Faster and easy construction as bricks can be
Slow construction as it is difficult to get proper
arranged easily and proper bonding can be
bonding and skilled labour is required.
achieved using mortar
Labour cost is more Labour cost is less

Poor bonding but more strength Good bonding but less strength

Dressing of stone is required Dressing is not required

Thin walls cannot be constructed. Minimum Thinner walls can be made even of 10 cm
thickness of wall is 30 cm. thickness.
Required lifting devices for lifting and placing of
Lifting and placing of bricks is easy.
stones
More quantity of mortar is required Only less quantity of mortar is needed

Plastering is not needed Plastering is needed to increase durability.

Self-weight is more Self-weight is less

Irregular and continuous joints Regular joints and rarely continuous

More water tight construction Susceptible to moisture absorption

Heavy ornamental work can be done Only light ornamental work can be done

Advantages and limitations of masonry construction Advantages

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Module III Dept. of Civil Engineering, MEAEC

 The use of material such as bricks and stones can increase the thermal mass of a building and can
 protect the building from fire.
 Masonry is non-combustible product.
 Masonry walls are more resistant to projectiles, such as debris from hurricanes or tornadoes
Disadvantages
 Masonry can be expensive and time-consuming to use.
  Expense
One of the first disadvantages of building with masonry is the high cost of both materials and
labor. While wooden homes have materials that can be purchased at many home supply stores,
brick, stone and other masonry construction involves products that are extremely heavy, cannot
be delivered in a conventional vehicle and often must be ordered from a special catalog. The
expense of selecting and moving the materials is compounded because masonry construction
cannot be conducted in a heavy rain or under freezing conditions. Installation also requires
excessive construction time and manpower with highly specialized skills.

  Maintenance
Once built, of course, a brick or stone home exterior provides a beautiful fa9ade year round. This
luxury exterior, however, is also expensive after the initial construction and requires a rigorous
maintenance schedule to keep it looking as good as new. While wooden structures can bend
slightly with the settling of the foundation, masonry structures rely completely on their
foundation for stability. This means that as the house settles, cracks can form that can let in
moisture. If these cracks are not repaired, the resulting moisture intrusion can cause structural
problems up to and including collapse of the damaged portion of the building.
• Additions
Building an addition is also more difficult when the house is built in masonry. Although brick
homes do sometimes have wooden additions, the original congruity of the home is ruined and
the home does not heat or cool in the same way throughout the house. The alternative, making
an addition to the home using the same masonry methods, is a return to the expensive and
labor-intensive process of the original construction.
• Weight
Masonry construction is much sturdier than wooden homes because of the thickness, hardness
and weight of the materials used to build the home. While this can be an advantage in some
areas, the weight of a brick or stone construction can lead to premature and extensive sinking of
the foundation.

COMPOSITEWALL
When walls are constructed with two or more types building materials, it is termed as composite
masonry.
The composite masonry is adopted due to following reasons:-
1. It reduces overall cost of construction.
2. It improves the appearance of the structure by concealing the inferior work.
3. It makes the use of locally available materials, to obtain optimum economy.
The usual combinations adopted to obtain composite masonry can be listed as below:-
1. Stone Facing with brick backing.
2. Stone slab Facing with brick baking.
3. Brick Facing with concrete baking.
4. Ashlar facing with brick backing.
5. Ashlar facing with rubble backing.
Advantages
 Reduces the overall cost of construction
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 Dept. of Civil Engineering, MEAEC Module III
 Makes the structure more durable
 Minimize the effects of atmospheric gases on the wall
 Makes the structure aesthetically more sound
Disadvantages
 Create large number of mortar joints in the inside than at the outside of the wall which leads
to unequal settlement

CAVITY WALL
 A cavity or hollow wall consists of two separate walls, called leaves or skins, with a cavity or a gap
 in between them.
 Two leaves may be of equal or unequal thickness

 Former arrangement is adopted for non-load bearing wall and in the latter arrangement, the
 internal leaf may be made thicker than the external leaf to meet with the structural requirement
  The skins are commonly masonry such as brick or concrete block.
 Masonry is an absorbent material, and therefore will slowly draw rainwater or even humidity
into the wall.

 The cavity serves as a way to drain this water back out through weep holes at the base of the
wall system or above windows, but is not necessarily vented.

 Reasons of providing cavity walls are prevention of dampness, heat and sound insulation and also
it is very economical
Main Functions of Walls
 Strength
 Stability
 Weather exclusion
 Thermal Insulation
 Sound Insulation
 Durability
 Fire resistance
 Appearance

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Module III Dept. of Civil Engineering, MEAEC
Construction

 In general, cavity wall doesn’t require

any footings under it, just a strong
concrete base is provided on which
cavity wall is constructed centrally.
Two leaves are constructed like
normal masonry, but minimum cavity
must be provided in between them.
The cavity may be filled with lean
concrete with some slope at top up to
few centimeters above ground level
 as shown below.
  Weep holes are provided for outer leaf
at bottom with an interval of 1 m. Normal bricks are used for inner leaf and facing bricks are used
for outer leaf. Different masonry is also used for cavity wall leaves. The leaves are connected by
 metal ties or wall ties, which are generally made of steel and are rust proof.
 The maximum horizontal spacing of wall ties is 900mm and maximum vertical spacing is 450mm.
The wall ties are provided in such a way that they do not carry any moisture from outer leaf to
 inner leaf.
 For half brick thickness leaves, stretcher bond is provided. And for one brick thickness or more
thickness, English bond or Flemish bonds type constructions are provided. While laying bricks,
 care should be taken without filling the cavity with cement mortar.
 To prevent mortar dropping in cavity, wooden battens are provided in the cavity with suitable
dimensions. These battens are supported on wall ties and whenever the height of next wall tie
 location is reached, then the battens are removed using wires or ropes and wall ties are provided.
 Two leaves should be constructed simultaneously. Spacing should be uniform and it is attained by
predetermining the location of wall ties. Damp proof course is provided for two leaves separately. In
case of doors and windows, weep holes are provided above the damp proof course.
Cavity Wall Insulators:
 Cavity wall insulation is used to reduce heat loss through a cavity wall by filling the air space with
 material that inhibits heat transfer.
 This is because up to 35% of the heat loss from your property is through the walls.
Advantages of Cavity Walls.
 The moisture cannot enter from outer wall to inner wall , since there is no direct contact.
  Provide good insulation against sound.
 Protection against efflorescence.
 Proves economical during construction.
 Load on the foundation is reduced.
 Reduction of heat transfer, since air layer between leaves acts as non-conductor of heat.

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 Dept. of Civil Engineering, MEAEC Module III
PARTITION WALLS
 A partition wall may be defined as a wall or division made up of bricks, studding, glass or other such
 material and provided for the purpose of dividing one room or portion of a room from another.
 Partition walls are designed as non-load bearing walls. It may be of folding, collapsible or fixed type.
 If partition walls are load bearing then they are called as ‘internal wall’.
Advantages of partition walls
 Divide the whole area into a number of rooms.
  Provide privacy to the inmates from sight and sound.
 Are light in weight and cheaper in cost of construction.
 Occupy lesser area
 Easily constructed in any position.
Requirements of a good partition wall:

  Thin in cross-section so that maximum floor area can be utilized.

 Provide adequate privacy in rooms both in respect of sight and sound.
 Constructed from light, sound, uniform, homogeneous, durable and sound insulated materials.

 Simple in nature, easy and economical inconstruction having proper coherence with the type of
 building structure.
 Offer sufficient resistance against fire, heat, dampness, white ant or fungus, etc.
 Rigid enough to take the vibrations caused due to loads.
 Strong enough to support sanitary fittings and heavy fixtures.
Types of Partition Walls:
(a) Brick partitions,
(b) Hollow block partitions,
(c) Clay block partitions,
(d) Concrete partitions,
(e) Glass block partitions,
(f) Wooden partitions,
(g) Straw board partitions,
(h) Plaster slab partitions,
(i) Metal partitions,
(j) Asbestos cement partitions, and
(k) Double glazed window.
(a) Brick partition
 Constructed with plain bricks, Reinforced bricks, bricks-nogged or hollow bricks.
  Plain brick partition of half brick thickness is not more than 2m in height.
 In reinforced brick partition of half brick thickness, reinforcement in theform of wire mesh or
 hoop iron or steel bars is provided.
 Brick nogging partition wall consists of brickwork built up within a framework of wooden
 members.
 Brick partition is fire-resistant and sound-proof.

i. Plain brick partition

 This type of wall is constructed by laying bricks as stretchers in cement mortar. Thus the
wall is generally 10cm (half brick) thick and plastered considerably on both faces. If
properly constructed, it is considerably strong and fire resistant.

 Reinforced brick wall

 This type of wall is similar to plain brick partition wall except that at every third or fourth
course, the bricks are reinforced with iron straps 25 to 28 mm wide and 1.6mm thick.

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Module III Dept. of Civil Engineering, MEAEC
Mild steel bars 6mm spaced at every third course of wall may be used as a substitute
for iron straps.
ii. Brick nogging type partition wall
It consists of brickwork built within a framework of wooden members. The framework
consists of vertical posts called studs spaced at 60 cm to 150 cm apart and held in position by
horizontal members called nogging pieces. The nogging pieces are housed into the studs at
60 cm to 90cm apart vertically. The function of the wooden framework is to increase stability
of the wall both along the length and height and to make it more right to withstand
vibrational effect produced on account of careless opening or closing of the window or door
leaves. The brickwork is built by laying the brick flat or on edge and the surface is plastered
from both sides. Thus the size of the studs and nogging depends upon the thickness of
partition wall. For 10cm thick partition wall, the studs and nogging should be 15 cm wide so
that after the brickwork is plastered from both the faces, the timber framework may finish
flush with the wall face. This type of partition wall suffers from the drawback of the timber
getting delayed. Moreover, the mortar used may not stick well to the timber members and
thus the brickwork is likely to become loose after sometime.
(b) Hollow Block and Clay Block Partitions

 Hollow blocks moulded from clay, terracotta or concrete are now

commonly used for the construction of partition walls. Such walls
are light, rigid, economical, strong and fire resistant. They have
good sound insulating properties. The sizes of the blocks differ with
the texture of the material. The thickness of this type of partition
wall varies between 6 cm to 15 cm. these walls are constructed in
 similar manner as structural load bearing walls.
  Hollow concrete block partitions are built of individual units of concrete.
 Clay blocks used are well prepared from clay or terra-cotta, and they are either solids or hollow.

 Hollow clay blocks of section 30*20 cm with thickness varying from 5 cm to 15 cm can also
 be used.
 The blocks are provided with grooves on top, bottom and sides, surfaces are kept glazed in
different colures.

(c) Concrete partition

 Partition walls construction in concrete, plain or reinforced may be cast in situ or built from
panels or blocks, precast wall in advance of the commencement of work. Generally for cast in situ
walls, 10 cm thick and below, the reinforcement consisting of mild steel bars or B R C fabric is
placed in the centre of the wall thickness. Concrete mix usually adopted in the work is M15
(1:2:4). The wall is cast monolithically with the intermediate columns so as to be rigid and stable
both along its length and height. In case of precast concrete partition walls, precast concrete slab
 panels and special shaped concrete post are used. The slabs are generally 32
mm thick and are inserted in the grooves of the precast post and the joints are subsequently
filled with mortar.
  It can be either precast or cast in-situ.
 Special concrete posts are used for the construction of precast concrete partition walls.
 Heavy weight

(d) Glass partition

 These may be made from sheet glass or hollow glass bricks. In case of sheet glass partitions,
Sheets of glass are fixed in the framework of wooden members dividing the entirearea into a
number of panels. The panels may be square or rectangular and their size varies with the
choice of the individual. Glass partitions are cheap, light, and easy in construction and
provide reasonable privacy and sound insulation. The cost of maintenance of such partition is
much more as glass is liable to break when struck hard by anything. With the introduction of

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 Dept. of Civil Engineering, MEAEC Module III
reinforced glass sheets, this danger is greatly minimized. Three-ply glass and armour plate
glass are some of the varieties of sheet glass.
 Are made from sheet glass or hollow glass blocks.
 Provides good aesthetics and allow light
  Are damp, sound and heat proof.
 Easy to clean and maintain.
 Sheets of glass are fixed in the frame work of wooden or metal.
 Hollow blocks doesn’t need timber framework.

(e) Wooden partition

 This type of partition walls consists of a wooden framework either supported on the floor
below or by side walls. The framework consists of a rigid arrangement of timber members
which may be plastered or covered with boarding etc from both the sides. Such partitions are
not fire-resistant and the timber forming the partition is likely to decay or be eaten away by
white ants. With the introduction of new building materials, the use of timber partitions is
 getting gradually reduced these days.
 Lighter in weight and easy to construct.
  Neither sound-proof nor fire-proof.
 Not suitable for damp locations.

(f) Strawboard partitions
 Useful where removal of partitions is frequent.
 Made of compressed straw covered thick paper or hardboard.
  Easy to construct.
 Heat and sound proof partitions.

(g) Plaster slab partitions
 In order to achieve improved insulation against heat and sound, metal lath and plaster
partition walls can also be made with a cavity between the wall thickness. This type of
hollow partition wall is constructed by fixing the metal lath on both sides of specially
shaped steel channels spaced at 30 to 45 cm apart. Depending upon the width of cavity
desired, the channels are generally 3 to 10cm deep.
 Are made of burnt gypsum or plaster of paris mixed with sawdust.
 5cm to 10cm thick slabs are prepared in iron or timber moulds.
 To form rigid joints suitable grooves are provided in the plaster slabs.
 Nails and screws can be easily driven into these slabs.

(h) Metal partitions
 Are light in weight, fireproof and strong.
 Are easy to construct and shift.
 Insulated material is filled into hollow spaces.
 Used for office and industrial buildings.
 Are also formed of metal lathes supported and fixed by wires.

(i) Asbestos Cement or GI partitions

 Partition walls constructed from asbestos cement sheeting or galvanized sheet fixed to
wooden or steel members are mostly adopted in works of temporary character. These walls
 are economical, light and fairly rigid if constructed properly.
 For superior type of asbestos cement sheet partition walls, specially manufactured slabs of
the above said material are used. Each slab consists of core or corrugated asbestos cement
sheet with the plain asbestos cement sheet attached to it on either side. The use of such
slabs renders the partition wall more fire-resistant and makes it have good heat and sound
insulation properties.

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Module III Dept. of Civil Engineering, MEAEC

  Light in weight, impervious, durable, water tight and fire-proof.

 Asbestos cement sheets are made of asbestos cement sheets and fixed into timber framework.
 Sheets are placed in position and joined by cement mortar.
 Are mostly adopted in works of temporary character.

(j) Double Glazed window
 Used for acoustic insulation.
 Air space between two panes is kept 50mm or more.
 Air contained within narrow cavity is quite ‘stiff’
 Transmits vibration at low frequencies.

(k) Movable partitions
 Movable partitions are used where the walls of a room are frequently opened to form one
large floor area.

 There are three types of partitions:

(l) Portable Partitions

 Rolling mobile folding partitions which provide temporary walls

 The portable wall partition has two full panel end members which provide
 support, rigidity, privacy, and noise reduction.
 They fold and are on wheels enabling mobility and ease of storage.

 Three common uses are:

 To divide space quickly where non-mobile permanent room dividers may
 be unavailable or unpractical.
  As a cost effective way to create a classroom or meeting room in existing space.
 Convenient sight divider to conceal door openings to restrooms, commercial
kitchens, and other backroom areas.

 Portable Partitions are commonly used in:

 Arena’s
 Churches/Houses of Worship/Funeral Homes
  Conference/Convention Centres
 Government/Corporate offices
 Hotels/Restaurants
 Residences
  Salons and Spas
 Schools of all levels

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Dept. of Civil Engineering, MEAEC Module III
SCAFFOLDING
There is a limit to the safe working height at which a worker can access the building work from
ground level. Therefore some form of temporary support is required to provide a safe and
convenient working surface. This is known as scaffold or scaffolding. Scaffolding is used on new-build
projects and for work to existing structures, including maintenance and repair work. The temporary
structure needs to be structurally safe yet also capable of rapid erection, disassembly and reuse.
Scaffolding is a temporary rigid structure made of steel, bamboo or timber. The primary aim of
constructing a scaffold is to create a platform on which mason can work at different heights.
Scaffolds also help to lift materials for the immediate uses at different heights.
Functional requirements
 Provide a safe working horizontal platform
 Provide safe horizontal and vertical access to buildings
A competent person must inspect the whole of the scaffolding and associated temporary supports,
including the tying in and sections that are welded, bolted and fabricated off site, prior to use. The
inspection must be recorded in the site log. Subsequently the structure must be checked on a
regular basis to ensure it remains safe throughout its use. Scaffolding and temporary works should
always be checked before use following extreme weather conditions eg. strong winds.
Scaffold components
Standard: A standard is a long pipe or tube that connects the mass of the scaffold directly to the
ground, and it runs the length of the scaffolding.
The base of each standard is connected to a base plate, which helps distribute the weight each
standard bears. It spreads cross sectional area of standards to a larger area. it prevents sinking of
standard. It prevents overturning of scaffold.
In between each standard, running horizontally, is a ledger, which adds further support and weight
distribution .it is a lengthwise scaffold tube that extends from standard to standard that supports
the transoms and that forms a tie between the standards
Transoms: Placed on top of ledgers at a right angle, come in several different forms. Main transoms
provide support for standards by holding them in position as well as supporting boards.
Intermediate transoms are placed alongside main transoms to lend additional board support.
Coupler: a component or device used to fix scaffold tubes together.
Plank: an individual timber board or fabricated component thet serves as a flooring member of a
platform.
Handrail/Guardrail: a barrier consisting of pipes erected to prevent workers from falling off an
elevated work area.
Toe board: a barrier min 150mm height to prevent slip/fall of materials from platform.
Mudsill (sole plate): it is a wooden plate that is used to distribute the scaffolding load over a
suitable ground area.
Braces, such as Cross braces, fa9ade braces, and additional couplers, can be used in varying
combinations to support the structure in several ways. Cross braces run diagonally between ledgers
and securely attach to standards to increase a structure’s overall rigidity. However, the can also
secure themselves to ledgers, in which case they are simply called ledger braces. Fa9ade braces help
prevent a structure from swaying, and are attached on the face of the scaffold, running the length of
the face of the structure and securely attaching at every level.

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Module III Dept. of Civil Engineering, MEAEC

General Scaffold Requirements

 Scaffold components must be able to support at least four times their maximum intended load.

 The scaffolding platform should be fully planked, with no more than a 1-inch gap between
 planks or planks and uprights.
 The gap between the last plank and the uprights should be less than 9/ inches.
 All platforms should be at least 18 inches wide.
  Guardrail systems or personal fall-arrest systems should be employed where needed.
 The scaffold (minus the guardrail) should be 14 inches or less from the work face, or 18 inches
for plastering and lathing.
 Planks should not extend past the ends of the scaffold frames more than 12 inches.
 Casters must be locked before work begins.
  Platform surfaces should be secured and cleated.
 The platform should be free from clutter and any tripping hazards.
 Scaffolding, material and workers must remain at least 10 feet away from power lines.
 The top and bottom plank surfaces should be visible and free from opaque finishes.
 Abutted planks must rest on separate support surfaces.
  Scaffolding components made by different manufacturers must fit together without force.
 A defective scaffold must be removed from service.
Scaffolding types that are commonly used
There are 5 types of scaffolding commonly used in construction works. Each of them are briefly
described below.

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Dept. of Civil Engineering, MEAEC Module III
(a) Supported Scaffolding
This is the most commonly used form of
scaffolding and is the type that you will see
being used in construction work and on
most other forms of work where elevation
is required. Extra support may be required
if the scaffolding will be long or required to
take a lot of weight.
Supported scaffolding is built from the base
upwards, and will normally be used
wherever possible. It is considered the
easiest, most convenient, safest, and most
cost effective form of scaffolding construct. Different forms of supported scaffolding are
available, and each will serve a very specific purpose and used in specific circumstances.
(b) Suspended Scaffolding
In suspended scaffolding, the working platform is suspended from roofs with the help of wire
ropes or chains etc., it can be raised or lowered to our required level. This type of scaffolding is
used for repair works, pointing, paintings etc..
It is used when constructing a base is difficult or impossible. It is often used when workers need
access to upper levels where building from the ground is impractical. Window cleaners
sometimes use this type of scaffolding to clean tower block windows. It is often seen when
repairs are needed for upper levels too.

(c) Rolling Scaffolding

Rolling scaffolding is a similar type of construct to supported scaffolding, but rather than offering
a stable base, it uses castor style wheels that enable the base to be moved. This is a useful form
of scaffolding when you need to complete work over a longer distance than a single scaffolding
construction would permit.
The wheels should be locked when workers or materials are on the scaffolding, in order to
ensure the safety of those using it, and those around it.

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Module III Dept. of Civil Engineering, MEAEC
(d) Aerial Lifts
They are also known as aerial platforms. The most common are
vehicle- mounted aerial platforms (scissor type), and vehicle-
mounted aerial lifts with telescopic and rotating boom. Aerial lifts
should be used where workers need to be able to access a number
of levels in order to be able to complete a construction. For
example, if building work is being completed on the outside of a
multi-storey property and both workers and materials will be
needed to work outside two or more floors, at different times, then
an aerial lift will make it easier and safer to lift even large amounts
of material, and multiple workers to the levels required
(e) Mobile Scaffolding
There are a number of factors to consider when deciding whether to use static or mobile
scaffolding. Ease of access is one such consideration, along with the amount of movement on
the scaffolding itself. Where possible, you should rely on the use of a single scaffolding
structure, or a number of structures, because mobile units, while perfectly safe when well-
constructed and used properly, do pose more of a hazard than mobile constructs.
Most scaffolding is considered semi-permanent. Once used, it can be taken apart and moved to
another location before it is constructed again. Fixed scaffolding can be left in position for
longer periods of time, making it especially useful in those situations where permanent access
may be needed to elevated positions.
Comparison of different types of scaffolding
Supported Suspended Rolling Scaffolding Aerial Lifts
Scaffolding Scaffolding
It is comparatively Access very high levels
It is easy to install. It is very convenient.
cheap to install. very quickly.
It is considered very It is ideal for just one or It allows work to be The number of people
safe. two workers. carried out over longer that may use them at
elevated areas. one time is limited.
It is mobile, which
It is very convenient and It allows people to reach reduces the need for It is the fastest way of
flexible in terms of very high levels on frequent dismantling getting to a higher level
application/use. buildings. to move it. using scaffolding.

OTHER TYPES OF SCAFFOLDING

The following 4 types of scaffolding are commonly used in building construction work.
a. Brick layer’s Scaffolding or Single Scaffolding
b. Mason’s Scaffolding or Double Scaffolding
c. Steel or Tubular Scaffolding
d. Needle Scaffolding or Cantilever Scaffolding
(a) Single scaffolding / brick layer’s scaffolding
Single scaffolding is generally used for brick masonry and is also called as brick layer’s scaffolding.
Single scaffolding consists of standards, ledgers, putlogs etc
In this type of scaffolding, a series of vertical members made of bamboo or timber (named as
Standards), are firmly fixed into the ground in a row parallel to the building wall. The distance in
between two standards is generally kept within 2.4 to 3 m.

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 Dept. of Civil Engineering, MEAEC Module III
These standards are connected to each by a longitudinal
horizontal member (named as Ledgers). Ledgers are tied with
standards at every rise of 120 cm to150 cm (i.e. 4 ft to 5 ft).
Rope lashing is used to tie the standard with ledgers.
The putlogs (or transverse horizontal members) are placed at a
horizontal spacing of 120 cm such that one end is supported on
the ledgers and the other end is held in the holes made in the
wall. Rope lashing is used to fasten the putlogs with ledgers.
If the height of the scaffolding is very high, to maintain its
stability, sometimes diagonal members (named as Braces) are
provided. Braces are cross diagonally fitted with the standards
using rope lashing.
(b) Double scaffolding / mason’s scaffolding
This type of scaffolding is commonly used in case
of stone masonry. It is stronger than brick layer’s
scaffolding. In stone walls, it is hard to make
holes in the wall to support putlogs. So, two rows
of scaffolding is constructed to make it strong.
The first row is 20 - 30 cm away from the wall
and the other one is 1m away from the first row.
Then putlogs are placed which are supported by
the both frames. To make it more strong rakers
and cross braces are provided. This is also called
as independent scaffolding.

The primary differences between brick layer’s

scaffolding and mason’s scaffolding are as
follow:

  In case of brick layer’s scaffolding single

row of standard is fixed into the ground. But in case of mason’s scaffolding two rows of
standards are fixed into the ground. First row of standards is fixed close to the wall and
second row of standard is fixed at a distance of 1.5 m from the first row. This is why it is
named as double scaffolding.

 In case of brick layer’s scaffolding one end of putlog is fixed with wall. But in double
scaffolding, putlogs are not fixed with the wall. Put logs are supported at both ends on
ledgers. Therefore mason’s scaffolding is completely independent of the wall surface.
And there is no need to make any hole on the wall surface.

(c) Steel or tubular scaffolding
Steel scaffolding is constructed by steel tubes which are fixed together by steel couplers or
fittings. The method of construction of steel scaffolding is similar to that of brick layers and
mason’s scaffolding. The primary differences are
 Instead of using timber, steel tube of diameter of 40 m to 60 mm are used
  Instead of using rope lashing, special types of steel couples are used for fastening
 Instead of fixing the standards into the ground, it is placed on base plate
The gap between two standards in a row is generally kept within 2.5 m to 3 m. These standards
are fixed on a square or round steel plate (known as Base Plate) by means of welding.
Ledgers are spaced at every rise of 1.8 m. Length of the putlogs are normally 1.2 m to 1.8m.
Advantages of the Steel Scaffolds are as follow:

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Module III Dept. of Civil Engineering, MEAEC
 It can be erected or dismantled more rapidly in comparison to timber scaffolding. This
 helps in saving construction time.
 It is more durable than timber. Therefore it is economical in long run.
  It has more fire resisting capacity
 It is more suitable and safe to work at any height.

(d) Needle scaffolding / cantilever scaffolding
Needle scaffolding or cantilever scaffolding is required in the following cases
 When it is not possible to fix standard into the ground
 When construction is done on the side of a busy street
 When construction work is carried out at very high level in case of tall building
In this type of scaffolding instead of fixing the standard into
the ground, it is placed at some height above the ground
level. The platform on which stands are placed is called
needle. A needle is a cantilever structure, made of timber,
projected out from the holes in wall.
To prevent lifting up of the needle, the inside end of the
needles are supported by struts wedged between the
needles and the head pieces.
The projected outward end of the needle is supported by an
inclined strut which rests on the window sill.
The joints between the inclined strut and the needle are
clamped by means of dogs.

COST EFFECTIVE CONSTRUCTION

The important need and everyone’s dream is to have their own home with individual needs. Since
India is a developing country, the economy has importance and the cost based construction has an
important role to play. There are various cost effective techniques of construction and lots of them
are also energy efficient and easily adoptable
The application of sustainable and cost effective technologies for better housing in rural and urban
areas is an urgent need considering spiraling construction costs. There is a need for the adoption of
strong, durable, environment friendly, ecologically appropriate, energy efficient and yet cost
effective materials and appropriate technologies in construction. Laurie Baker is one who worked on
cost effective construction techniques in our state. Baker showed that sustainable technologies
combined with creativity, could lead to unique architectural expressions which can move the expert
and the layman alike.
Proper materials are the basic need to develop any construction technique. Brick, wood and stone
are three major materials which can be used in India for any type of construction.
Factors affecting cost estimation of construction
 Building cost:-The building construction cost can be divided two parts namely: Building
 materials cost 65 to 70% and labour cost 65 to 70%
Now in low cost housing, building material cost is less because locally available materials are used
and also the labour cost can be reduced by properly making the time schedule of our work. Cost
reduction is achieved by selection of more efficient material or by an improved design.

 Size:-The smaller the project in terms of scope or the number of square feet, the more will be
the cost per square feet.

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 Dept. of Civil Engineering, MEAEC Module III
 Type:-Different types of project have different levels of complexity and detailing.

 Special construction:-Complexity can greatly increase the cost of the project. For example-
Renovation of a structure especially if altering or moving structural components are required,
can be costly because it necessities demolition as well as building. Special construction may
also be necessary to shield surrounding space from noise, fire and other hazards.

 Other factors affecting the budget of any structure are
 Project accessibility
 Labour rates
 Material cost
 Time of year
 General economic pressures
Cost Effective Building Materials
1. Stabilized compressed earth blocks: A good material which can be used for masonry. It is
economical, stronger, energy saving and simple for manufacture.
2. Fly ash Gypsum stabilized mud blocks: The excavated soil is mixed in the adequate proportion with
the appropriate stabilizer. It is important that the sieved soil be dry/ protected from the rain before
being used. A block-making machine is used for the creation of stabilized mud blocks. A measured
amount of sieved soil, quarry dust, sand/cement or lime is put in the block-making machine mould.
They are much stronger with less water absorption and cheaper than bricks. Stabilized earth blocks
are designed to take heavy loads, replacing the widely used reinforced concrete columns. It can be
used for roofs and walls alike. They are much stronger with less water absorption and cheaper than
cement stabilized blocks. With 5 to 10% flyash- G, 30% saving in cement could be achieved in
addition to utilization of the waste product like flyash.
3. Precast stone blocks of larger size than normal bricks are manufactured by using waste stone
pieces of various sizes with lean cement concrete and enable a rationalized use of natural
locally available materials.
4. Precast concrete blocks made to similar dimension of stone blocks without large size stone
pieces, but using coarse and fine graded cement. They have excellent properties comparable
to other masonry blocks, are cheaper and facilitate speedy construction and especially suitable
where quality clay for bricks making is not available.
5. Flyash- lime gypsum products manufactured by blending flyash lime and calcined gypsum for
making a useful product named Fal-G , and can be used a cementations material for
mortar/plaster and for masonry blocks of any desired strength. It can also be used for road
pavements and plain concrete in the form of Fal- G concrete.
6. Clay red mud burnt bricks produced from alumina red mud or bauxite, an industrial waste of
aluminium producing plants in combination with clay. Possess all the physical properties of
normal clay bricks and solves the problem of disposal of the waste product and environmental
pollution. In addition, they have good architectural value as facing bricks due to their pleasing
hues of color.
Cost Effective Construction Technologies
(1) Foundation

  Random rubble masonry in mud/cement mortar placed in excavation over thick sand bed.
 Use lean cement concrete mix 1:8:16 for base with brick masonry in 1:6 cement for mortar
 footing
 Suggested to adopt arch foundation in ordinary soil for effecting reduction in construction
cost up to 40%. Arch foundations require less digging, material, and being a relatively labor-
 intensive process, put more laborers to work.
 In the case black cotton and other soft soils it is recommend to use under ream pile foundation
which saves about 20 to 25% in cost over the conventional method of construction.

(2) Plinth
 The plinth slab which is normally adopted can be avoided and in its place brick on edge can
be used for reducing the cost.
CE 204 – Construction Technology 3.33 | Page
Module III Dept. of Civil Engineering, MEAEC
 It is recommended to adopt 1 ft. height above ground level for the plinth and may be
 constructed with a cement mortar of 1:6.
 The plinth slab of 4 to 6" which is normally adopted can be avoided and in its place brick on
edge can be used for reducing the cost. By adopting this procedure the cost of plinth
foundation can be reduced by about 35 to 50%.

(3) Walls
 Brick work in 1:6 cement mortar using bricks from soil like black cotton soil stabilized with fly
 ash.
 Rat trap bond brick masonry is preferred in 1:2:12 cement lime mortar and 1:5:3 cement
sand mortar.
  Compressed mud blocks masonry in mud mortar
 Wall thickness of 6 to 9" is recommended for adoption in the construction of walls all-round
 the building and 41/2” for inside walls.
 It is suggested to use burnt bricks which are immersed in water for 24 hours and then shall
be used for the walls.
 Making use of Rat - trap bond wall & Concrete block wall.
 Brick jali can be used instead of parapet wall or boundary walls.
  Concrete block walling
In view of high energy consumption by burnt brick it is suggested to use concrete block (block
hollow and solid) which consumes about only 1/3 of the energy of the burnt bricks in its
production. Concrete block masonry saves mortar consumption, speedy construction of wall
resulting in higher output of labor, plastering can be avoided thereby an overall saving of 10
to 25% can be achieved.

  Soil cement block technology
This method of construction of wall is by soil cement blocks in place of burnt bricks
masonry. It is an energy efficient method of construction where soil mixed with 5% and
above cement and pressed in hand operated machine and cured well and then used in the
masonry. The overall economy that could be achieved with the soil cement technology is
about 15 to 20% compared to conventional method of construction.

(4) Roof

 Domes and vaults in brick or stabilized mud blocks

with appropriate mortar.
 Thatch roof on appropriate frame work
 Precast RCC ‘L’ panel.
  Burned clay roofing in vault form.
 Ferro cement channel - Provide an economic solution to RCC slab by providing 30 to 40% cost
reduction on floor/roof unit over RCC slabs without compromising the strength. These being
precast, construction is speedy, economical due to avoidance of shuttering and facilitate
quality control.

(5) Roof/Intermediate slabs
 Thin R.C.C. Ribbed slabs
 RC.C. panels and joists in M15 concrete.
 Precast R.C.C. joists and brick panels.
 Bamboo reinforced concrete.
  Normally 5" thick R.C.C. slabs is used for roofing of residential buildings.
 By adopting rationally designed construction practices like filler slab and precast elements
the construction cost of roofing can be reduced by about 20 to 25%.

(6) Doors and windows

 It is suggested not to use wood for doors and window frames and in its place concrete or
steel section frames shall be used for achieving saving in cost up to 30 to 40%.
 Plantation timber styles with particle board inserts.
 Medium density fiber board doors.
 Cement bonded particle board
 Plantation timber style with rice husk board inserts
3.34 | Page CE 204 – Construction Technology
 Dept. of Civil Engineering, MEAEC Module III
 Red mud polymer panel doors.
 Ferrocement doors
  Polyvinyl chloride doors panels.
 Door and window frames are not actually required. They are responsible for almost half the
 cost of timber used. Avoiding frames considerably reduces the cost of timber.
 Door planks are screwed together with strap iron hinges to form doors, and this can be
carried by holdfast fittings carried into the wall. The simplest and most cost-effective door
can be made of vertical planks held together with horizontal or diagonal battens

(7) Lintels and Chhajjas

 The traditional R.C.C lintels which are costly can be replaced by brick arches for small spans
 and save construction cost up to 80-40% over the tradition method of construction.
 By adopting arches of different shapes a good architectural pleasing appearance can be given
to the external wall surfaces of the brick masonry.
 Locally available stone slabs can be used.

(8) Door panel
 Plantation timber styles with particle board inserts
 Medium density fiber board doors
 Cement bonded particle boards

(9) Finishing work
The cost of finishing items like sanitary, electricity, painting etc. varies depending upon the type,
quantity and cost of products used in finishing. Reduction is left to the individual choice and liking.
(10) Techniques to reduce cost from area

  Reduce plinth area by using thinner wall concept.

 Use locally available material in an innovative form like soil cement blocks in place of burnt
 brick.
 Use energy efficiency materials which consume less energy like concrete block in place of
 burnt brick.
 Use environmentally friendly materials which are substitute for conventional building
 components like use R.C.C. Door and window frames in place of wooden frames.
 Preplan every component of a house and rationalize the design procedure for reducing the
 size of the component in the building.
 By planning each and every component of a house the wastage of materials due to
demolition of the unplanned component of the house can be avoided.
FILLER SLAB
The reason why, concrete and steel are used together to construct RCC slab, is in their individual
properties as separate building materials and their individual limitation. Concrete is good in taking
compression and steel is good in tension. Thus RCC slab is a product which resists both compression
as well as tensile.
 They are normal RCC slabs where bottom half (tension) concrete portions are replaced by filler
 materials such as bricks, tiles, cellular concrete blocks, etc
 These filler materials are so placed as not to compromise structural strength, result in
 replacing unwanted and nonfunctional tension concrete, thus resulting in economy.
 These are safe, sound and provide aesthetically pleasing pattern ceilings and also need no
plaster.
The filler slab is a mechanism to replace the concrete in the tension zone. The filler material thus is not a
structural part of the slab. By reducing the quantity and weight of materials the roof become light and less
expensive. Yet it retains the strength of conventional slab. The most popular filler material is roofing tiles.
Mangalore tiles are placed between steel ribs and concrete is poured in to the gap making a filler slab. The
filler slab uses less steel and cement and it is also a good heat insulator.

CE 204 – Construction Technology 3.35 | Page

Module III Dept. of Civil Engineering, MEAEC

Conventional tests by different institutions and laboratories have proved that the load bearing
capacity of filler slab is not less when compared to the conventional R.C.C. slab. Since filler roof tiles
are firmly bonded to and covered by concrete, it does not collapse under impact of say a coconut
falling on the roof.
Designing a filler slab requires a structural engineer to determine the spacing between the
reinforcement bars.
Advantages of filler slab
 For roofs which are simply supported, the filler slabs results in lower loads getting transferred to
 the load bearing walls and the foundations.
 Weight of slab is reduced by the introduction of a less heavy filler material like two layers of
 burnt clay tiles. Lab thickness is min 112.5 mm.
 Enhances thermal comfort inside the building due to heat resistant qualities of filler material and
 the gap between two burnt clay tiles.
 Makes saving in cost. Cost of this slab is reduced when compared to the traditional slab by about
23%.
  Consumes less concrete and saves cement and steel by about 40%.
 Leak proofing - With proper supervision and workmanship, leaks can be avoided. The chance of
 leak in a filler slab is much than the conventional R.C.C. slab.
 Patterned ceilings - Filler slabs provide aesthetically pleasing patterned ceilings. In most houses
the filler material is left without plastering to form aesthetically pleasing patterned ceilings .But
some residences prefer to plaster the slab with cement mortar or provide a coating of plaster of
 Paris.
 Thermal insulation - The air pocket formed by the contains of the tiles make an excellent thermal
insulation layer. The design integrity of a filler slab involves careful planning, taking in to account
the negative zones and reinforced areas.
RAT TRAP BOND MASONRY
A rat trap bond masonry technique is a type of brick masonry bond in which bricks are laid on edges
(i.e. the height of each course, in case of a brick of size 230 x 110 x 75 mm, will be 110 m plus mortar
thickness) and it is a technique where the bricks are used in a way which creates a cavity within the
wall.
The cavity helps to maintain improved thermal comfort and keep the interiors colder than outside
and vice versa. Also materials like brick, clay and cement can be considerably saved. This adds this
technology to the list of green building technologies. This is an appropriate sustainable option as

3.36 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module III
against conventional solid brick wall masonry.
The rat trap bond construction is a modular type of masonry construction. Due care must be taken
while designing the length and height of walls and size of openings of a structure. The openings and
wall dimensions should be in multiples of the module. Also the course below sill and lintel should be
solid course by placing brick on edge. The masonry on the sides of the openings also should be solid
which will help in fixing of the frames of openings.

Advantages of Rat-trap bond masonry


Rat trap bond wall is a cavity wall construction with added advantages of thermal comfort. The
 interiors remain cooler in summer and warmer in winters.
 By adopting this method of masonry we can save approximately 20-35% less bricks and 30-50%
less mortar. Also this reduces the cost of a 9 inch wall by 20-30% and the productivity of work
 enhances.
3
 For 1 m of rat trap bond 470 bricks are required, compared to conventional brick wall where
 550 bricks are required.
 Rat trap bond when kept exposed, create aesthetically pleasing wall surface and cost of
plastering and painting of walls also may be avoided.
 Rat-trap bond can be used for load bearing as well as thick partition walls.
  All works such as pillars, sill bond, window and tie beams can be concealed.
 The walls have approx. 2% less dead weight and hence the foundations and other supporting
structural members can suitably be designed. This given an added advantage of cost saving
for foundation.
  Services installations should be planned during the masonry construction if not exposed.
 Materials such as bricks, cement and steel can be considerably saved upon by adopting this
technology. It will also help to reduce the embedded energy of materials and reduce the
 production of greenhouse gases in the atmosphere.
 For more structural safety, reinforced bars can be inserted through the cavity till the foundation.
Material saving
 16% of bricks are less used.
 54% of sand is less used.
 57% of cement is less used.

*******************************
Prepared By
NAJEEB. M
Assistant Professor
Dept. of Civil Engineering
MEA Engineering College

CE 204 – Construction Technology 3.37 | Page

MODULE 4
Dept. of Civil Engineering, MEAEC Module IV
MODULE 4
Syllabus:
Lintels and arches – types and construction details.
Floors and flooring – different types of floors and floor coverings
Roofs and roof coverings – different types of roofs – suitability –types and uses of roofing materials
Doors, windows and ventilators – Types and construction details
Finishing works – Plastering, pointing, white washing, colour washing, distempering, painting.
Methods of providing DPC. Termite proofing.

FLOORS AND FLOOR COVERING

Floors arc the horizontal elements of a building which divide building into different levels for the
purpose of creating more accommodation one above other within the limited space. Floor just above the
ground level-is called ground floor and the floors above ground level are upper floors. These are known as
first floor, second floor etc. with reference to ground floor. Floors below the natural ground are called as
basement floor. An intermediate floor between two floors of any storey forming an integral part of floor
below is called mezzanine floor. A floor consist or two main components.

a) A sub-floor (or base course or sub grade) that provides proper support to the floor covering and
all loads carried on it. It imparts strength and stability to floor.
b) A floor covering (or flooring or paving) is a covering over subfloor which provides a smooth,
clean, impervious and durable surface .
TYPES OF FLOORS
It is divided into Ground floor & Upper floor
1. Ground Floor
It rests directly on ground. Apart from giving good finished surface, these floors should have good
damp resistance. The ground surface is rammed well and a layer of red earth or sand is placed which
is compacted. A layer of broken bricks, stones etc. is provided up to 150 mm below floor finish level
and rammed. While ramming the surface is kept moist to get good compaction. Then 1 : 4 : 8
concrete of 100 to 150 mm thickness is provided as base course. Over this bed floor finish is laid.
Materials used for ground floor construction are
i. Bricks
ii. Stones
iii. Timber
iv. Concrete
Bricks, stones and concrete are laid above ground to desired height and over that suitable floor
covering is done. Timber joists are laid above the concrete layer and the gap between floor and
concrete is filled with sand to form timber floor.
2. UPPER FLOOR
They are classified on the arrangement of beams and girders or the frame work for supporting the
flooring. They are
i. Timber floors
Single joist floor: joists are placed 30 cm center to center supporting on wall plates. Corbels
are also requires to support joists, if the width of wall is less. Wooden planks of thickness 4
cm thick are placed over joists. These are easy to construct and requires less initial cost.
Distribution of loads on the wall is more uniform as the joists are spaced closely. But the
joists may slag and hence cracks will develop in ceilings. They are not sound proof.

CE 204 – Construction Technology 4.1 | Page

Module IV Dept. of Civil Engineering, MEAEC

Double joist timber floors: They are used for longer spans of 3.6- 7.5 and prevent the travel of
sound waves to a great extent. Intermediate supports called binders are placed to support
joists. Binders are placed at a centre-to- centre distance of about 2 m. The ends of binders are
kept on or stone blocks and they are not embedded in the masonry wall.

This is a more rigid type of flooring and, hence, there is less chance of developing cracks in the
plastered ceiling. It is more soundproof. Often wall plates maybe avoided by the use of
binders. The depth of the floor is considerably increased and thus the head room is reduced.
Framed timber floors: This type of timber floor is used for spans of more than 7 m. Girders arc
placed between the walls and binders are put on the girders and the bridging joists rest on
the binders. The spacing between girders depends on size of binders. Girders are supported
on stones or templates on the walls.

ii. Jack Arch Floor

In this, brick or concrete arches are provided between the lower flanges of rolled steel Joists
with spacing not more than 1.5m. Steel bars are provided at end spans. The rise of the arch is
normally kept one-fifth of span. These are rigidly fixed on walls; the side filling is done with
lime concrete etc. Pl; ceiling is not obtained when jack arch floors are used.

4.2 | Page CE 204 – Construction Technology

Dept. of Civil Engineering, MEAEC Module IV
iii. Filler Joist Floor
Rolled steel joists encased in the concrete arc used in this type of floor. The joists are
supported on walls or on side beams. Then the spaces between joists are filled with cement
concrete.
iv. Steel Joist and Flagstone Floor
In this, rolled steel joists are placed are places at suitable intervals supporting on walls or
edge beams. Flag stones of 40 mm are placed on · top flange and bottom flange of the joist
and the empty space is filled with selected earth or concrete. Precast concrete slabs also
may be used instead of flag stones.
v. RCC Floor
Reinforced Cement Concrete (RCC) floors are the most popular t: of floor construction in the
modern era. The slabs are directly cast over beams or wall supports. Continuous floor is cast
on frame work of beams in a framed type building constructions. A suitable thickness of l0
cm to 25mm is normally adopted based on the design. Beams are cast monolithically with
slabs to form a combined structure in the case of framed structure. Suitable floor covering is
adopted over the slabs.

vi. Flat Slab Floor

In this system of floors, beams are avoided and slabs are directly supported by columns.
Column heads or drops are constructed at column top. this is very advantageous because of
less form work required for floor construction compared to normal beam-slab construction.
False ceiling is not required in this type of floors. More head room is also available in flat
slab constructions. Also it gives more aesthetic appearance.
vii. RCC or Hollow Brick-ribbed Floor
These floors are used when to reduce the weight of the floor. Hollow blocks or tiles with clay
or cement are placed in the gaps of steel reinforcement m slab. Then the empty spaces are
filled up concrete. The floor acts as RCC floor but with light weight. This floor is economical,
fire resistant, sound proof and damp roof.

viii. Pre-cast Concrete Floor

With the advancement of concrete technology and construction methods, it is now
possible to cast suitable elements of floors with concrete and place it over the walls or
beams. Precast units are jointed and grouted with cement mortar at site. Suitable floor
covering is adopted over the floor. No formwork is required for this type of construction;
this saves both time and money.

CE 204 – Construction Technology 4.3 | Page

Module IV Dept. of Civil Engineering, MEAEC

SELECTION OF FLOORINGS
Every flooring has its own merits and demerits that there is not even a single type which can be
suitably provided under all circumstances. Floors have to serve different purposes in different types of
building. The following actors govern the selection of floorings.
(1) Initial Cost: The cost of construction is an important factor in the election of the type of floor.
Floor covering of marbles, granite, vitrified tiles, etc. is considered to be very expensive
whereas cork, slate, vinyl, tile, etc. are moderately expensive. Concrete and brick floors are
cheapest type of floor construction. The cost of both floor covering and sub-floor has to be
accounted while comparison.
(2) Appearance: Flooring should achieve the desired colour effect and architectural beauty
according to the use in the building. Generally flooring of terrazzo, mosaic, tiles, marble and
cement concrete provides a good appearance whereas asphalt covering and mud flooring etc.
give an ugly appearance.
(3) Durability: The flooring material should offer sufficient resistance to wear and tear, temperature,
chemical action, etc. So as to provide long life .From the durability point of view, flooring of marble,
terrazzo, tiles and concrete is considered to be good. Flooring of other materials such as linoleum,
rubber, cork, bricks, timber etc. can be used where heavy floor use is not anticipated.
(4) Cleanliness: A Floor should be non-absorbent and could be easily effectively cleaned. All joints
in flooring should be watertight. Moreover, greasy and oily substances should neither spoil the
appearance nor have destroying effect on the flooring materials. Floorings with terrazzo,
marble, tiles and slates arc generally found suitable for cleanliness.
(5) Sound Insulation: According to modern building concepts, a floor should neither create noise
nor transmit noise. For buildings like hospitals, libraries: libraries, studios etc.it is required that
any movement on the top floors should not disturb the persons working on the other floors.
Suitable flooring is provided in such situations. Cork tile and rubber floorings have excellent
sound insulation properties. Timber and linoleum flooring has poor sound insulation.
(6) Dump-resistance: All the floors, especially ground floors, should be damp - resistant to ensure a
healthy environment. Normally, floors of clay tiles, terrazzo, concrete, bricks, etc. are preferred
for use where the floors are subjected to dampness. Floorings with wood, rubber, linoleum,
cork etc. arc easily vulnerable to dampness.
(7) Thermal Insulation: Flooring materials play an important role in maintaining the temperature
inside the building even the temperature changes outside. This reduces the cost of demand for
heating in winter and refrigerating in summer. The floors with wood, cork etc. are best suited
for this purpose
(8) Hardness: It is desirable to have good resistance against scratches, impressions and imprints
when used for either supporting the loads or moving the loads over floors. Normally the hard
surfaces rendered by concrete, marble, stone, etc. do not exhibit any impressions whereas the
coverings like asphalt, cork, plastic, etc. get scratched when used.
(9) Smoothness: The floor covering should have smooth and even surface However, at the same
time, it should not be too slippery which will cause unsafe movements over it, particularly by
old people and children. Floor coverings with terrazzo, concrete, tiles are suitable in this aspect.
Antiskid tiles are also available in various trade names in the market.
(10) Fire Resistance: This is also another important factor in selection of upper floors. These floors
are to act as highly resistant fire barriers on which rescue operations take place. Hence flooring
materials should have sufficient fire resistance. All combustible flooring materials like wood,
cork, plastic etc. should be used over fire resistant base only.
4.4 | Page CE 204 – Construction Technology
Dept. of Civil Engineering, MEAEC Module IV
(11) Maintenance: It is always expected that maintenance cost should be as low as possible.
Generally a covering of tiles, marble, terrazzo or concrete requires less maintenance cost as
compared to the floors of wood blocks, cork etc.
FLOOR COVERINGS
Floor coverings or floor finishes are provided above the floors to improve the appearance, cleanliness,
sound proofing and damp proofing. A variety of materials are used for floor coverings. These are selected
based on the requirements and uses of the floors. Various types are briefly explained below.
1. Mud and Mooram flooring
Mud flooring is usually used in villages for their huts and other unimportant buildings. These are
cheap and easy to construct and maintain. Mud floor is hard, impervious and has good thermal
insulation capacity. For mud floor construction, 25-30 cm thick layer of selected moist earth is spread
over a bed and it rammed well to get a thickness of 15-20cm. Chopped straw is also mixed in the
earth to prevent drying cracks on the floor. When mooram (disintegrated rocks, especially Laterite) is
used for making mud flooring instead of earth, it is called mooram flooring.
2. Stone floor covering
Square or rectangular slabs of suitable stones like granite, sand stone or marble are used for this type
of flooring. Normally 20-40 mm thick stones of sizes of30 cm x 30 cm, 45 cm x45 cm, 60 cm x 60 cm,
45 cm x 60 cm etc. are used. The stones used should be hard, durable, tough and good quality, the
earthen base is levelled, compacted and watered. Over this a layer of 10-15 cm thick concrete is
placed and properly rammed. Over this concrete a thin layer of mortar is laid. Before fixing the stone
slabs in position, their edges and the joints are finished with cement. The stone surface maybe rough
or polished. A slope of l in 40 is provided in such type of floor covering for proper drainage.
3. Brick floor covering
Brick floors are used for cheap constructions like go-downs, barracks stores etc. These are commonly
used in alluvial places where brick earth is available in plenty and stones are scare. First of all, a well
compacted and levelled ground is prepared. Then a lean mix of concrete of 1:3:6 or so is placed over
for a thickness of 15cm. Then the bricks are laid in parallel set in cement. The joints are then pointed
for better appearance and durability. This flooring is non-slippery, hard and durable. The initial cost is
less compared to cement concrete. But this flooring is water absorbent.
4. Concrete floor covering
The most popular type of flooring used in these days is concrete flooring in all types of buildings. It has
two parts namely
a. A base course or the sub grade and
b. A wearing course or floor finish
The concrete flooring consists of a topping of cement concrete 2.5- 4 cm thick laid on a 10'-15 cm
base of either lime or cement concrete. A flushing coat with rich cement slurry mixed with red or
black colour pigment is also applied over this for better appearance. The actual construction
operation consists of the following steps.
a. Ground preparation
b. formation of base course
c. Laying of topping concrete
d. Laying of wearing coat
e. Grinding and polishing and
f. Curing
Concrete flooring is non-absorbent and hence offers sufficient resistance to dampness. It possesses
high durability and, hence, is employed for floors in kitchens, toilets, schools, hospitals, etc. It
provides a smooth, hard, even and pleasing surface and can be cleaned easily. Concrete flooring fire-
resistant and can be used for fire resistant purposes in the buildings.

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Module IV Dept. of Civil Engineering, MEAEC
But defects once developed in concrete floors, whether due to poor workmanship or materials,
cannot be easily rectified. The concrete flooring is difficult to repair by patchwork satisfactorily. It
possesses poor insulation properties against sound and heat.
5. Mosaic floor covering
This type of floor finish is commonly used in operation theatres, temples, brooms, etc. For this
construction, first a concrete base is constructed for laying the floor covering. Over this, while it is
still wet, lime or cement mortar is placed to a depth of about 2 cm and it is levelled up. A layer of
cementing material about 3 mm in thickness is spread. The cementing material consists two parts of
slaked lime, one part of powdered marble and one part of powdered marble and pozzolana. After 4-5
hours of laying this cementing material, a mixture of coloured cement and small pieces of broken
glazed tiles (popularly known as mosaic chips) are laid. This is compacted with a light roller. This
surface is for 24 hours and then it is rubbed with pumice stone or mechanical grinders to get a
smooth and polished surface. The polished surface is left for about 2 weeks before use.
6. Terrazzo floor covering
Terrazzo is a special type of concrete with cement and marble chips as aggregates. Flooring laid with
this concrete is polished with carborundum stone to obtain a smooth finish at the top. Any desired
colour is obtained by adding marble chips of different colour or using colored cements. The base for
this e of floor covering is concrete and is laid in the ordinary method. Over the 3 mm concrete base, a
thin layer of sand is sprinkled evenly and it is covered tar paper. A layer of rich mortar is spread over
it and then terrazzo mixture is placed over it evenly. Marble chips of 3-6 mm are mixed with white or
cured cement in the proportion 1 2 or I :3 to get the terrazzo mixture. Dividing strips of metal, 20
gauges thick, (sometimes glass strips) are inserted into mortar base to form the desired patterns.
Terrazzo mixture is laid in the formed between the metal strips. The terrazzo is levelled in position
trowel.
When the terrazzo has hardened, the surface is rubbed by coarse fine carborundum stones,
respectively to get a smooth finished surface is kept wet with water while rubbing. The surface is
cleaned with soap sol and then wax polish is applied to the surface. This type of floor covering costly
and is used to obtain a clean, attractive and durable surface in public buildings, hospitals bathrooms,
etc. It requires more time to finish terrazzo flooring.
7. Timber floor covering
Timber floor covering is the oldest type, but nowadays it is used for some special-purpose floors
such as theatres, dancing halls, carpentry rooms and hospitals. It is preferred in hill places because
of its good thermal insulation properties. It possesses natural beauty and has enough resistance to
wear. But prevention from dampness is very important in the case of timber flooring. Timber floor
covering may be carried out in the following types:
a. Strip floor covering: This is made up of narrow and thin strips timber which are joined to
each other by tongue and groove joints.
b. Planked floor covering: In this type of construction, wider planks are employed and these are
joined by tongue and groove joints.
c. Wood block floor covering: It consists of wooden blocks are laid in suitable designs over a
concrete base. The thickness of a block20-40 mm and its size varies from 20 X 8 to 30 X 8 cm.
The blocks properly joined together with the ends of the grains exposed.
d. Parquet floor covering: This is the same type of wood block floor where thin blocks (max. I0
mm) are used instead of thicker ones.
8. Tiled floor covering
Tiled flooring has become the most popular one now a days and extensively used in all types of
buildings including public, semi-public, residential, commercial and industrial buildings. The prime
advantages of this flooring shorter time of installation, pleasing appearance and durability. Tiles are
directly on the concrete or other hard base with a thin layer of mortar. Adhesives are also available
to paste these on surfaces. Flooring tiles are available sizes from 20cm x 20cm to 120 x 120 and also
in any shades and designs.

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Dept. of Civil Engineering, MEAEC Module IV
For laying tiles on ground or basement, first the ground for receiving is level lied, well watered and
rammed. Then a sub grade of I0 to 15 cm thick lime or cement concrete is placed. Then a layer of 1:3
cement mortars is spread over it and levelled it. After it hardened for few hours, neat cement slurry
is poured over it. Then tiles are placed over it with utmost care using cement paste applied on its
sides. After 2-3 days, joints are rubbed off and cleaned. For upper floors, normally on RCC floors, sub
grade with cement concrete is not required.
Tiled flooring provides a non-absorbent, decorative and durable surface. Installation is fast and
possible to repair in patches. These are generally costly compared to other floorings. Terracotta
(earthen ware) tiles, ceramic tiles, vitrified tiles, glazed tiles, cement concrete tiles and terrazzo are
the important varieties of tiles used in tiled flooring.
9. Marble floor covering
Naturally available marble slabs are directly laid over a sub grade set in cement mortar. Then it is
polished with carborandum stones. Though s costly, it has the properties of hardness, durability and
aesthetic appearance. is flooring is adopted in superior type of constructions and places where
sanitation and cleanliness are important like hospitals, theatres, places of worships and toilets etc .

10. Granite floor covering

Granite slabs arc also naturally available in different colours and textures. These are laid in the
similar way of marble and possess better qualities than marble.
11. Rubber floor covering
These are used in public and industrial buildings because of their good wearing qualities. It has good
elasticity and noise insulation properties. It is made of pure rubber mixed with cotton fibre,
granulated cork or asbestos, fibre and the desired colouring pigments. The thickness of rubber
sheets or tiles varies from 3 to 10 mm and it is available in many designs and patterns .The tiles or
sheets and can be cemented over the dry base of concrete or wood by means of special adhesives.
The rubber floor coverings arc expensive t provide a durable wearing surface.
12. Linoleum floor covering
Linoleum is the floor covering which is generally laid over wooden or concrete floors. It is the
fabricated form of a mixture of resins, linseed oil, gums, pigments, wood flour, and cork dust and filler
materials. It is available in market in rolls of width about 2-4 m. The thickness varies from 2 to 6mm.
These tiles are also manufactured in various sizes, shapes and patterns. This can be laid over the
floors or pasted with adhesives on the floors. Also linoleum coverings are prepared over wooden
bases and nailed over the timber floor bases.
This flooring provides an attractive, resilient durable and economical surface. It offers a surface that
can be easily washed and cleaned. Being moderately warm with cushioning effect, linoleum provides
comfortable living and working conditions. It offers adequate insulation against noise and heat. But
it is subjected to rotting when kept wet for enough time and its use is not suitable for basements. It
has poor resistance against fire, being combustible in nature. This covering when applied over a
wooden base get them under excessive sub-floor traffic.
13. Glass floor covering
It is used when it is desired to allow light to the floor below. Structural glass is available in the form
slabs or tiles of thickness 10 to 30 mm. They are fitted within frames of different types. The
members of the frame are designed in such a way that the glass floor covering can take up
superimposed loads without breaking. This type of floor covering is not common.
14. Plastic or PVC floor covering
The plastic tiles are made of PVC (Poly Vinyl Chloride). Plastic or thermoplastic tiles can be
economically used as floor covering on the concrete floor base. It is not preferred over wooden floor
base as the preparation of the wooden surface for receiving the tiles is very costly. Plastic floor
covering are used in all types of buildings like offices, hospitals, shops, schools.

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Module IV Dept. of Civil Engineering, MEAEC
15. Magnesite floor covering
Magnesite flooring is known as composition flooring or joint less flooring. It is composed ofa dry
mixture of magnesium oxide, a pigment and inert filler materials, e.g., wood flour, asbestos or
sawdust. Liquid magnesium chloride added to this powder and a plastic material is obtained at site.
This plastic material is spread over the floor and the surface is levelled with a trowel can be directly
laid over stone, concrete or wooden floor base. It is economical and is used as floor covering for
office buildings, schools, factories, etc.

ROOFING
Roof is the uppermost part of the building provided as structural covering, to protect the build
mg from weathering agencies like sun, rain, wind etc. The roof, as a structural element supports the
roof covering. Structural element may be truss, beam, slab, shell or dome. The roof covering may be
of corrugated sheets, tiles, slates or slab.
REQUIREMENTS OF AN IDEAL ROOF
1. It should protect the building from weathering agencies like sun, rain, wind etc.
2. It should be durable.
3. Roof should be water proof with good drainage arrangements.
4. It should be fire resistant.
5. Should have adequate strength and stability.
6. It should have thermal and sound insulation properties.
TYPES OF ROOFS
Generally roofs can be classified into the following categories based on its geometry.
1. Pitched or sloping roofs
2. Flat roofs
3. Curved roofs
Pitched or sloping roofs
Pitched roofs are sloped roofs. The slope is given towards different sides. Since the top surface
is sloped, the drainage is excellent in these roofs. Buildings with irregular shapes cannot have pitched
roofs effectively. In the areas of heavy rain falls and snow fall sloping roof are used. The slope of roof
shall be more than 10°. They may have slopes as much as 45° to 60° also. The sloping roofs are
preferred in large spanned structures like workshops, factory buildings and ware houses.
Terms:
1. Span: It is the clear distance between the supports of roof.
2. Rise: It is the vertical distance between the top of the ridge and wall plate
3. Pitch: It is the slope of the roof. It is obtained as the ratio of rise to span.
4. Ridge: It is the apex line of the sloping roof.
5. Eaves: The lower edge of the inclined roof surface is called eaves.
6. Hip: Itis the ridge formed by joining of two sloping surfaces; external angle is greater than 180.
7. Valley: It is a reverse of a hip.It is formed by the intersection of two roof surfaces, making an
external angle less than 180.
8. Principal rafter: This is the inclined member running from the ridge to the eaves.
9. Purlins: These are horizontal wooden or steel members, used to support roofing material of a
roof. Purlins are supported on trusses or walls.
10. Wall plates: These are long wooden members, which are provided on the top of stone or brick
wall, for the purpose of fixing the feet of principal rafters.
11. Battens: These are thin strips of wood, called scantlings, which are nailed to the rafters for lying
roof materials above.
12. Cleats. These are short sections of wood or steel, which are fixed on the principal rafters of
trusses to support the purlins.

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Dept. of Civil Engineering, MEAEC Module IV
13. Truss: A roof truss is a framework, usually of well-fanned triangles designed to support the roof
covering or ceiling over rooms.

Types of Pitched roofs

A. Single Roof
1. Lean to roof
It is used to cover veranda. It has span upto 2.5 m. The
rafters are suitably secured on the wall-plates and
eaves boards, battens and roof covering is provided. It
is generally used for sheds, out-houses attached to
main buildings, verandahs, etc.

2. Couple roof
In this type of roof, the common rafters
slope upwards from the opposite walls and
they meet on a ridge piece in the middle.
The common rafters are firmly secured in
position at both the ends, one end being on
the ridge piece and the other on the wall
plate. This type of roof is used for span up
to about 3.60 m
3. Couple close roof
This roof is similar to couple roof except that
the legs of common rafter is connected by a tie, preventing the spread out and overturning of
walls. This type of roofs are adopted economically up to a span of 4.20 m

4. Collar tie roof

This roof is variation of couple close roof. The tie beam is raised and placed at a higher level. The
tie beam is the known as a collar or a collar beam. A collar beam is adopted to economize the
space and to increase the height of room. The collar beam is usually fixed at one-third to one-half
the vertical height from the ridge. The roof can be adopted up to a maximum span of 4.80m.

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Module IV Dept. of Civil Engineering, MEAEC

B. Double or Purlin Roofs

 These roofs have two basic elements:
 (i) rafters and (ii) purlins.
 Purlin gives intermediate support to the
rafters which in turn reducesthe size of
 the rafters to the economical range.
 It is also known as rafter and purlin
 roof.
  Used when span exceeds 5m.
 The rafters are provided at 20 to 40 cm
 c/c spacing.
 Each rafter is supported at three
 points: ridge, purlin and wall plate.
 For larger roofs, two or more purlins may
be provided to support each rafter.

C. Triple Membered/Trussed Roofs
 In this system, the roof consists of 3 elements:
a) Rafters to support the roofing material
b) Purlins to provide intermediate support to rafters
c) Trusses to provide support to the ends of
purlins.  A trussed roof is provided when
o The span of the room is greater than 5 meters
o When the length of the room is large i.e., (where there are no internal walls or
partitions to support the purlins)
1. King post truss
A king post truss has two principal rafters, a tie beam, and a central vertical king post. It is
suitable for spans of 6 to 9m.

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 Dept. of Civil Engineering, MEAEC Module IV
2. Queen post truss
It consists of two queen posts and s straining beam. Here straining beam and strut are under
compression .Queen post and tie beams are under tension. It is suitable for spans upto 13.5 m.

3. Combination of King-Post and Queen-Post trusses

  For greater spans, the queen post truss can be strengthened by one
 more upright member, called princess-post to each side
 Suitable upto 18m span

4. Mansard roof truss

 Is a 2 storey truss with upper portion consisting of the king-post truss and the lower portion
 of queen-post truss.
  It is thus a combination of king-post and queen-post trusses
 Mansard truss has 2 pitches. The upper pitch(King-Post truss) varies from 30 degrees to 40
 degrees and lower pitch(Queen-Post truss) varies from 60 degrees to 70 degrees
 A room may be provided in the roof between the two queen-posts
 Is not used now mainly because of its odd and ugly appearance

5. Truncated roof Truss

 Similar to Mansard roof truss except that
the top portion is finished flat with a
 gentle slope to one side.
 Used when it is required to provide a room
in the roof

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Module IV Dept. of Civil Engineering, MEAEC
Flat roofs
These roofs are nearly flat. However slight slope (not more than 10°) is given to drain out the rain
water. Flat roofs are suitable for places where rainfall is moderate, where there is no snowfall.
The advantages of flat roofs are:
 The roof can be used as a terrace for playing and celebrating functions.
  At any latter stage the roof can be converted as a floor by adding another storey.
 They can suit to any shape of the building.
 Over-head water tanks and other services can be located easily.
 They can be made fire proof easily compared to pitched roof.
The disadvantages of flat roofs are:
 They cannot cover large column free areas.

 Leakage problem may occur at latter date also due to development of cracks. Once leakage
 problem starts, it needs costly treatments.
 The dead weight of flat roofs is more.
 In places of snow fall flat roofs are to be avoided to reduce snow load.
  The initial cost of construction is more.
 Speed of construction of flat roofs is less.
Curved roofs
Curved roofs have the top surface curved. This is done with shells and domes. These are adopted
when large column free areas are required. Shell roof may be defined as a curved surface, the
thickness of which is small compared to the other dimensions. In these roofs lot of load is transferred
by membrane compression instead of by bending as in the case of conventional slab and beam
constructions. Caves are having natural shell roofs.
Advantages of shell roofs are:
 Good from aesthetic point of view
 Material consumption is quite less
 Form work can be removed early
 Large column free areas can be covered.
Disadvantages are:
 Top surface is curved and hence advantage of terrace is lost.
 Form work is costly.

STEEL ROOF TRUSSES

Steel trusses are suitable for large column free buildings like factories, auditoriums, cinema
halls, stadia etc. The situations where steel trusses are adopted:
 When large column free area required.
 When the span of the roof is more than 10 m.
 When the height of the roof is more compared to the ordinary buildings. -
 Where other roofs proved to be uneconomical.
 For speedy construction.

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Dept. of Civil Engineering, MEAEC Module IV
Steel trusses are fabricated from structural steel sections. Normally angle, channel, plate, T and tube
sections are used for fabrication of trusses. Various configurations are adopted for the trusses based
on its span.
The various configurations of truss are shown below. The suitable configuration is selected according
to the span of the truss.

Steel Roof Trusses

DETAILS OF STEEL ROOF TRUSS
Generally steel roof trusses are fabricated from angle sections and plates. But channel sections, T-
sections and tubular can also be used. The roof trusses are so designed that the members carry only
direct stress (i.e. either compression or tension) and no bending stress is induced· This is achieved by
allowing loads to be applied only at joints of the trusses. The principal rafters ( the top member) as
well as the main tie ( the bottom member) are generally made of built up sections like two angle
sections placed side-by-side etc. The inclined members are generally made of single angle sections.

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Module IV Dept. of Civil Engineering, MEAEC
The members are jointed together using a gusset plate either through rivet or by welding. At least
two rivets should be used at each joint. Gusset plate should not be less than 6 mm, though its
thickness is designed on the basis of forces carried by members to be jointed are connected to the
bearing plate. The bearing plate is jointed to-concrete bed through bolts. At the apex, suitable ridge
section is fitted.
Advantages of steel trusses
 They are economical compared to R.C.C. roofs
 Easy to construct and erect.
 Fire proof and resists termite attack.
 These are rigid and light.
 Maintenance is easy.
RCC ROOFS
 Made up of concrete and steel

 Two types of roof slab-one way slab and 2
 way slab
 In one way slab, main reinforcement is laid
 in the shorter span
 In 2 way slab, main reinforcement runs
 parallel to both sides of the room
 Easy to construct and it provides smooth
 finish
 Thickness of roof slab depends on type of
concrete used, span, floor loads etc

ROOF COVERINGS
Different materials are used for covering the steel trusses. Corrugated sheets made up of various
materials are suitable for steel trusses. The types of sheets are:
1. Asbestos cement sheets (A.C. sheets)
2. Galvanized iron corrugated sheets (G.l.) sheets
3. Aluminium sheets
4. FRP sheets (Fibre glass sheets)
5. Powder coated sheets
6. Roof tiles
7. Asphalt Shingles
A.C. sheets and G.I. sheets covering materials used for industrial buildings
1. A.C. sheets
These are widely used sheets for industrial buildings, factories, shed· cinema halls, auditoriums etc.
A.C. sheets are manufactured from asbestos which is a silky fibrous material, found in veins of
metamorphized volcanic rocks. It is mixed with Portland cement and these sheets are made. The
advantages of asbestos sheets are:

  They are cheap, light in weight and durable.

 Water tight, fire resisting and termite resistant.
 These are available in larger size, which makes the laying fast.
 A.C. sheets do not require any protective paints etc.
 Maintenance is also less
These sheets are available in three forms
 Corrugated sheets
 Semi-corrugated sheets
 Plain sheets

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Dept. of Civil Engineering, MEAEC Module IV

2. GI. sheets
Galvanized Iron sheet are also used for steel trusses. They are stronger than A C sheet. But these
sheets are costly. These are iron sheets galvanized with zinc to prevent rusting. These sheets are not
suitable for flatter slopes. These are mainly used in warehousing sheds, shelters. Security cabins,
garages, site cabins, bus stations. Ticket counters, parcel offices, shade-shelters. These sheets are
water proof with better impact strength and tire resistance. These are light in weight yet strong and
free from problems of cracking, warping and buckling.

3. Aluminium sheets
Another variety of roof sheet is aluminium sheets.
These are long lasting, economical than PVC, steel
and cement sheets and make inside atmosphere
cool. The most important advantage is that it is
corrosion free. This has almost zero maintenance
and eco healthy. No side effects on human body.
It has very good scrap value. It is light in weight
and with better appearance. These are used for
sheds, industrial buildings and temporary
constructions.

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Module IV Dept. of Civil Engineering, MEAEC
4. FRP sheets
Fibre Reinforced Polymer (FRP) sheets are made with glass or any suitable fibre with a suitable resin.
It is popularly known as fibre glass sheets. It is available in different colours and shapes. The
advantages are:
 UV Protected
  Does not warp or wilt.
 Non-combustible material of construction

 Can be easily cut, tooled, and handled at site with
 conventional tools.
 Resists tire corrosive action of chemicals and acidic
 vapours
 Rustproof.
 Lightweight
 High durability
 Does not absorb dust, grim, moss, or mildew.
  Virtually maintenance free
 High flexibility
 Can be bent perpendicular or parallel to the corrugation
 High thermal insulation
These sheets arc used for types of buildings and structures now a days because of its advantages over
other type of roofing materials.
5. Powder Coated Sheets
Conventional GI or Aluminium sheets are enhanced by applying powder coating on the surface. This
increases the life and improved the appearance. They are two types.
 Powder coated GI sheets
The GI Sheets arc coated with different coloured epoxy resins. These have excellent chemical
resistance and good mechanical properties. It minimizes the rusting of the GI sheets. It also gives
good appearance. It is also available in all patterns like corrugated, plain, traffored etc.
 Powder coated aluminium sheets
When aluminium sheets arc coated with epoxy resins, they are called powder coated aluminium
sheets. It improves the appearance and life. Different patterns are available viz. plain, corrugated,
trafford and etc. Unitiled coated aluminium sheets are another pattern which are very commonly
used now. This gives the appearance of a tiled roof building.
6. Roof tiles
 Roof tiles are thin members used for covering roofs made out of clay or concrete. They are of
 different shapes and sizes.
 Manufactured from clay
 Fire resistant, cheap and durable
 Tiles are better non-conductor of heat and cold

 Tiles are hung to the battens with projection which are already marked in tiles. They kept in
 position by a sort of interlocking action due to their self-weight
 Pitch of roof should be less than 40 degree

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 Dept. of Civil Engineering, MEAEC Module IV
7. Reinforced concrete roofs
The RCC slabs are classified into one way and as two way slab. When length of the slab more than
twice the width of the slab, it is called one-way slab and otherwise it is two way slab.
8. Asphalt Shingles
 Available in different colours
  They are easy to install, relatively affordable, last 20 to50 years
 Asphalt shingles do not do particularly well in climates that change drastically

DOOR
A door is a moveable barrier secured in a wall opening.
Functions:
 They admit ventilation and light.

 Controls the physical atmosphere within a space by enclosing it, excluding air drafts, so that
 interiors may be more effectively heated or cooled.
 They act as a barrier to noise.

 Used to screen areas of a building for aesthetic purposes, keeping formal and utility areas
separate.
Location of door in a building
 The number should be kept as minimum.
  It should meet the functional requirement.
 It should preferably be located at the corner of the room, nearly 20 cm from corner.
 If in a room, more than 2 doors are there, they shall be located facing each other.
Components of a door:
a) Door frame b) Door shutter
Door frame Door Shutter

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Module IV Dept. of Civil Engineering, MEAEC
Frame : It is an assembly of horizontal and vertical members, forming an enclosure, to which
the shutters are fixed
Shutters : These are the openable parts of a door or window.
Head : This is the top or uppermost horizontal part of frame
Horn : These are the horizontal projections of the head of a frame to facilitate the fixing of a
frame on the walls opening. The length of horns is kept about 10 to 15cm
Style : It is the vertical outside member of shutter
Top Rail : This is the top most horizontal member of a shutter
Bottom Rail : This is the lower most horizontal member of a shutter
Lock Rail : This is the middle horizontal rail where locking arrangement is fixed
Intermediate or Cross Rail: Additional horizontal rails fixed between top and bottom rail of a shutter
Panel : This is area of the shutter enclosed between the adjacent rails
Holdfasts : These are mild steel flats to fix or hold the frame to the opening
Rebate : It is the depression or recess made inside the door frame, to receive the door shutter
SIZES OF DOORS
The common width-height relations used:
 Width = 0.4 – 0.6 Height
 Height = (width +1.2)m
General sizes used:
a) Residential
External door – 1.0 x 2.0 to 1.1 x 2.0 m
Internal door – 0.9 x 2.0 to 1.0 x 2.0 m
Bath & WC – 0.7 X 2.0 to 0.8 x 2.0 m
Garages for cars – 2.25 x 2.25 m to 2.40 x 2.25 m
b) Public
1.2 x 2.0 m or 1.2 x 2.1 m or 1.2 x 2.25 m
DOOR FRAMES
Materials used for door frames
 Timber
 Steel
  Aluminium
 Concrete
 Stone
Timber door frame
General specifications:
 Timber is sawn in the direction of grains.
  All members of frames are of same species of timber and be straight without any warp.
 The frames are smooth, well planned surfaces except the surface touching wall lintel sill etc.
 The thickness of rebate is 15 mm and the width is equal to the thickness of shutter.

 Nominal size of door frame for single shutter is 75 X100 mm and for double shutter 75 X 125
 mm.
 The back portion of door frame which in contact with walls, lintels sill etc. is painted
 with bitumen or any anti-termite chemical.
 To protect door frame during construction priming coat is done before fixing.

 A minimum of 3 holdfasts shall be fixed on each side, one at the centre and the other two at
 300 mm from top and bottom of the frame.
 Holdfasts and other parts, which go into the masonry wall and thus not accessible for
maintenance, shall be protected against moisture and decay, with a coating of coal tar or
other suitable protective material.
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 Dept. of Civil Engineering, MEAEC Module IV
TYPES OF DOORS
Hinged doors
 Most doors are hinged along one side to allow the door to pivot
away from the doorway in one direction but not in the other. The
 axis of rotation is usually vertical.
 The most common door type. It is a simple & rigid.
 The panel swings, opens and closes, on hinges.

 Hinged doors require a minimum amount of maintenance and
cleaning, they are not expensive, and have an excellent insulating
 ability.
 However, they take up precious room space to swing in.
Battened and ledged door
 The door consists of vertical boards i.e. battens
and three or four horizontal ledges. The vertical
boards are tongue and grooved to stop draughts
and the edges chamfered to relieve the plain
 appearance.
 Battens : 100-150 mm wide and 20-30 mm thick
  Ledges : 200 mm wide and 25 – 30 mm thick
 The door is hung to the frame by T-hinges of
 iron.
 The door is commonly used for narrow openings
for internal use where it is not subject to hard
use, or where economy is of main consideration Battened Door Ledged Door
than the appearance.
Battened, Ledged and braced door
 Normally constructed using a Z-shaped frame with tongue-
and-groove interlocking boards attached they can be quite
heavy in weight but this can depend on the thickness of
boards used.

 Due to their construction they are normally very strong and
hardwearing and can also be planed and shaped to fit pretty
 much any door way.
 Such doors are used for wider openings.
 The braces incline down towards the hinged side.

Framed and Paneled door

 These types of doors are widely used in all types of buildings since they are strong and give better
 appearance than battened doors.
 Panel doors consist of vertical members called stiles and horizontal members called rails.
  Stiles and rails form the framework into which panels are inserted.
 Panels may be solid wood, plywood, particleboard or louvered or have glass inserts.
 Additional vertical members called mullions are used to divide the door into any number of panels.

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Module IV Dept. of Civil Engineering, MEAEC

Glazed or sash door

 This type is used in residential and public buildings.

 They supplement the natural lighting provided by windows or to make the interior of the room
 visible from adjoining rooms.
 They can be made fully glazed or partly glazed.

 Fully glazed doors are recommended where sufficient light is required through the door openings
 like in shopping malls, entrance halls etc.
rd rd
 In case of partly glazed, the bottom 1/3 part is usually paneled and upper 2/3 part is glazed.

Flush Door
  Flush doors are simply doors with a completely flat surface on both sides.
 Flush doors can come in solid format which is a door made of solid wood or hollow format which
is lightweight and comprised of two layers of thin timber separated, usually, by a lightweight
 honeycomb core. The core is covered with either hardboard or plywood on both sides.
 Solid flush doors are usually used as fire-check doors.
  Flush doors are lighter and cheaper than other types.
 The flush door shutters are manufactured in
 Standard thickness of 25, 30, 35 and 40 mm.

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 Dept. of Civil Engineering, MEAEC Module IV
Louvered doors
 A louvered door has fixed or movable wooden louvers which
permit open ventilation while preserving privacy and
 preventing the passage of light to the interior.
 They are most commonly used for bath and W.C. In residential
 and public buildings, where good ventilation is desired.
 The door may be louvered to its full height or may be partly
 louvered and partly paneled.
 The louvers are arranged in inclined fashion thus obstructs the
 vision but permits entry of air.
  Louvers may be fixed or movable.
 Louvers may be of timber, plywood or glass.
 However, they are difficult to clean.

Revolving doors
 Such types are provided in public buildings, like banks,
 museums, hotels, offices etc.
 A revolving door normally has four wings/leaves that
hang on a center shaft and rotate one way about a
 vertical axis within a round enclosure.
 The central shaft is fitted with ball bearing
arrangement at the bottom, which allows the shutters
 to move without any jerk and making noise.
 The radiating shutters may be fully paneled, fully
glazed or partly glazed. The glass doors allow people
to see and anticipate each other while walking
 through.
 People can walk out of and into the building at the
same time.
Sliding doors
 In these doors, the shutter slide horizontally along
tracks with the help of runners and rails. often for
 space or
 Sliding glass doors are common in places where there
 is no space to swing the door.
 Such doors are very popular for use for the entrances
to commercial structures and also in residential
 buildings for aesthetic considerations.
 Sliding doors consist of either one, two or three doors
that slide by each other on a track depending upon the
 size of opening and space available for sliding.
 They are pretty easily cleaned and maintained.
 These doors sound insulation is pretty poor usually, and
 they must be of high quality and fitted exactly in their tracks or else they may slide out of them.
 When fully open these doors will allow half the space of the opening in double sliding doors, or
 one third if triple.
 Sliding doors move along metal, wood, or vinyl tracks fitted into their frames at the top and
bottom. To ease their movement, sliding doors often have plastic rollers attached to the top and
 bottom or to the bottom only.
 The door is hung by two trolley hangers at the top of the door running in a concealed track while
at the bottom, rollers are provided to slide the shutter in a channel track.

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Module IV Dept. of Civil Engineering, MEAEC
Swing doors
 The shutter is fitted to its frame by special double
 action hinges.
 The hinges permits the shutter to move both ways, inward as
 well as outward.
  The doors are not rebated at the meeting styles.
 To open the door, a slight push is made and the spring action
 brings the shutter in closed position.
 The return of the shutter is with force and thus, the door shall
be either fully glazed Or provided with a peep hole at eye
level, to avoid accidents.

Folded doors
 Made of many narrow vertical strips or creases that fold back to
back into a compact bundle when doors are pushed open, these
 strips or creases will be hanged from the top, and run on a track.
 They save space as they do not swing out of the door opening,
though their sound and weather isolation is poor. Folding doors are
usually pretty noisy, and considered not so durable

Collapsible Door
 Such doors are used in garages, workshops, public buildings etc. to provide increased safety and
 protection to property.
 The doors do not require hinges to close or open
 the shutter nor the frame to hang them.
 It acts like a steel curtain.
  The door is made up from vertical double channels
 (20x10x2 mm), jointed together with the hollows
 on the inside to create a vertical gap.
 These channels are spaced at 100-120 mm apart
 and braced with diagonal iron flats.
 These diagonals allow the shutter to open or
 closed.
 The shutter operate between two rails, one fixed to the floor and other to the lintel.
 Rollers are mounted at the top and bottom.
Rolling shutter
 These are commonly used for shops, godowns,
 stores etc.
 The door shutter acts like a curtain and thus provides
adequate protection and safety against fire and thefts.
The shutter is made up of thin steel slabs called laths
or slates about 1.25 mm thick interlocked to each
other and coiled upon specially designed pipe shaft
called drum mounted at the top.

 The shutter moves in two vertical steel guide
 channels installed at their ends.
 The channel is made up of steel sheets and deep
enough to accommodate the shutter and to keep it in position.
  A horizontal shaft and spring in the drum which allow the shutter to coiled in or out.
 These may be manually operated for smaller openings (upto 10 sq.m.). Above 10 sq. m., they may
be operated manually.

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Dept. of Civil Engineering, MEAEC Module IV
WINDOWS
A window is comprised of two parts: (i) Window Frame, and (ii) Sashes or shutter frame.
Window frames are fixed to the opening in the wall, by means of suitable holdfasts. The sashes or
shutter are fixed to the window frames by means of suitable hinges.
The function of the window is to admit light and air to the room to give a view to the outside. It
should also provide insulation against heat loss and in some cases, against sound
The selection of size, shape, location and number of windows in a room depends upon the following
factors
(i). Size of the room
(ii). Location of the room
(iii). Utility of the room
(iv). Direction of wall
(v). Direction of wind
(vi). Climatic conditions such as humidity, temperature etc.
(vii). Requirements of exterior view
(viii). Architectural treatment to the exterior of the building
WINDOW PARTS
Frame : It is an assembly of horizontal and
vertical members, forming an enclosure,
to which the shutters are fixed
Shutters : These are the openable parts of a door
or window.
Head : This is the top or uppermost horizontal
part of frame
Sill : This is the lowermost or bottom
horizontal part of a window
Horn : These are the horizontal projections of
the head of a frame to facilitate the
fixing of a frame on the walls opening.
The length of horns is kept about 10 to
15cm
Style : It is the vertical outside member of
shutter
Top Rail : This is the top most horizontal member of a shutter
Bottom Rail : This is the lower most horizontal member of a shutter
Intermediate or Cross Rail: Additional horizontal rails fixed between top and bottom rail of a shutter
Panel : This is area of the shutter enclosed between the adjacent rails
Mullion : This is a vertical member of a frame, which is employed to sub-divide a window
opening
Holdfasts : These are mild steel flats to fix or hold the frame to the opening
Rebate : It is the depression or recess made inside the door frame, to receive the door shutter

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Module IV Dept. of Civil Engineering, MEAEC

TYPES OF WINDOWS
Fixed windows
 In this type, the glass pane is permanently fixed in
 the opening of the wall.
 The shutter can’t be opened or closed.

 The function is limited to allowing light and or
 permit vision in the room.
 No rebates are provided to the frame.
  The shutters are fully glazed.
 In homes they are generally decorative windows
near doors, stairwells and high-places or are used in
combination with other styles.

Pivoted windows
 In this type of window, the shutter is capable of
 rotating about a pivot fixed to window frame.
 The frame has no rebate.
 The shutter can swing horizontally or vertically.

Double-hung windows

 Special frames called boxed or cased frame

is used, which consists of two vertical
members spaced apart to create a groove
 to slide the shutter.
 A parting bead is provided in the groove of
 the frame to keep the two shutters apart.
 Only the bottom sash slides upward in a
single-hung window. In single-hung windows
the top sash is fixed and can’t be moved.

 It has two panes, top and bottom that slide
 up and down in tracks called stiles.
 The most common used windows
 today. When open, these windows allow air flow through half of its size.
  The two parts are not necessarily the same size.
 Traditionally, each shutter is provided with a pair of counterweights connected by cord or chain
 over pulleys.
 When the weights are pulled, the shutters open to required level.
  It is possible to have controlled ventilation.
 Sash windows may be fitted with simplex hinges which allow the window to be locked into hinges
on one side, while the rope on the other side is detached, allowing the window to be opened for
 escape or cleaning.
 Nowadays, most new double-hung sash windows use spring balances to support the sashes.

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 Dept. of Civil Engineering, MEAEC Module IV
Sliding Window or Slider:
 Has two or more sashes that overlap slightly but slide
 horizontally within the frame.
 Suitable openings or grooves are left in the frame or
wall to accommodate the shutters when are shutters
are opened.

Casement windows
 Casement windows are hinged at the sides.
  When fully opened, offer the maximum amount of ventilation.
 Operates like a hinged door, except that it opens and closes with a lever inside the window.
 The shutter consists of styles, top rail, bottom rail and intermediate rail.

 Depending upon the design, the frame can have additional vertical and horizontal members i.e.
 mullion and transom respectively.
 The panels may be either glazed, unglazed or partly glazed and are fixed in the grooves made in
rails and styles.
Glazed window
 This is a type of casement window where panels are fully glazed.
  The frame has styles, top rail and a bottom rail.
 The space between top and bottom rail is divided into number of panels with small timber
 members called, sash bars or glazing bars.
 The glass panels are cut 1.5-3.0 mm smaller in size than the panel size to permit movement of
 sash bars.
 Glass panes are fixed to sash bars by putty or by timber beads.
Louvered window
 They are provided for the sole function of ventilation and not
 for the vision outside.
 The styles are grooved to receive a series of louvers which may
 be of glass or wood slates.
 The louvers re usually fixed at 450 inclination sloping
 downward to the outside to run-off the rain water.
  The windows provide light and ventilation even if closed.
 Such windows are recommended for bath, WC, workshops
 etc., where privacy is more important.
 Venetian shutters uses louvers which can be opened or closed.
The louvers are pivoted at both ends in the frame and in
addition each blade is connected to a vertical batten by hinge.
Metal Windows
 These are very popular in public buildings and can be made up of mild steel, stainless steel,
 aluminium, bronze etc.
 Mils steel being cheapest of all, they are widely used. The windows can be fabricated for the
 required size using light rolled steel sections.
 They can be fixed directly to the wall opening in a wooden frame or in the steel frame.

 While fixing, care has to be taken that the members of the frame are not subjected to any
structural loads to prevent damage.

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Module IV Dept. of Civil Engineering, MEAEC
 Thus, the size of the window opening is kept slightly more than the frame size so as to allow some
 clearance between the two.
 The window is fixed into the opening only after masonry and lintel work is over and fully set.

 Advantages:
 They are more stronger and durable as compared to wooden windows.
 They are not subjected to expansion and contraction of joints.
 They are rot-proof, termite proof.
  Highly fire resistant.
 Presents better elegance and smooth finishing.
 Provide more area for light and ventilation.
 The cost of maintenance is negligible and thus proves economical.
Bay window
 The window projecting outward from the external walls.
 Wide and decoratively impressive allow for 180° view.

 A multi-panel window, with at least three panels set at different angles to create an extension
 from the wall line.
 it is commonly used in cold country where snow often falls.
 They may be triangular, circular, rectangular or polygonal in plan.

Corner window
 These are provided at the corner of the room.
  Light and air is admitted from two directions.
 The jamb post at the corner is made of heavy section.

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 Dept. of Civil Engineering, MEAEC Module IV

Dormer window
 Dormer window is a vertical window provided on the sloping roof
  Provides ventilation and lighting to enclosed space below the roof
• Very good appearance

Gable window
 It is a vertical window provided in the gable end of a pitched roof.

Skylight
 These are fixed windows on the sloping
 roofs.
 Admit natural light and help distribute light
more evenly throughout the room.
 Considered an energy saver feature.
 In addition to reducing the need to use
electric lights, it can deliver warmth in the
winter and cooling in the summer,
minimizing the need for fuel-based heating
and air conditioning. On winter days, the
sun’s radiant energy can shine through a
 south- or west-facing skylight to warm
interior surfaces. And in the summer, a ventilating skylight can promote air circulation by releasing
 the warm air that naturally rises.
 The opening for the window is made by cutting common rafters. The framework consist of
trimming pieces, curb frames, bottom rail and top rail. The opening is treated with lead flashings
 to ensure water proofing.
  Skylights may be plastic or glass, fixed or operable, and made in any number of sizes and styles.
 Ventilator: It is a narrow window of small height fitted near the roof of a room for ventilation. The
construction is similar to the fanlights. They are horizontally pivoted.
CE 204 – Construction Technology 4.27 | Page
Module IV Dept. of Civil Engineering, MEAEC
Ventilators
 Ventilators are small windows, fixed at a greater height than the window,
  Generally about 30 to 50 cm below roof level.
 The shatter can be opened or closed by means of two cords, one attached to the bottom rail and
 other one with top rail
 Top edge opens inside and bottom edge opens outside, so that rain water excluded

Fanlights
 The small window or ventilator fitted above the door or window frame separated by transom. The
function is to ensure cross ventilation in the room even if the door or windows are closed. They
also assist in admitting natural light.

PLASTERING
It is the process of covering rough walls and uneven surfaces in the constructions of houses and other
structures with a plaster or mortar.
Objectives of Plastering
- It is to provide an even, smooth, regular clean and durable finished surface
- To improve the appearance of the surface
- In order to protect the surfaces free from the effects of atmospheric agencies, plastering is
required.
- To conceal the defective workmanship.
- To cover up the use of inferior quality and porous materials of masonry work.
- To provide a satisfactory base for white washing, colour washing, painting or distempering.
Types of Plastering
There are basically four types of plastering. They are:
1. Lime plastering
2. Cement plastering
3. Mud plastering
4. Water proof plastering

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Dept. of Civil Engineering, MEAEC Module IV
Lime plaster - It is an intimate mixture of equal proportions of lime and sand, ground in a mortar mill
to form a paste of required consistency. Sand to be used in the mortar should not pass a 100 mesh
sieve for more than 5% or a 50 mesh sieve for more than 20% water and sand used should be clean
and free from all deleterious materials
Cement plasters - It is an intimate mixture of Portland cement and sand with required amount of
water to make a plaster mass. The proportion of cement and sand depends upon the nature of work.
The ingredients are first mixed in a dry state and water is added to make a paste. This plaster should
be used within 30 minutes since starts setting after 30 minutes.
Mud plasters - It is prepared with equal volumes of clay or brick earth and of chooped straw, hay,
loose soil or cowdung and hemp. The ingredients are mixed and left for 7 days with large quantity of
water. Then, it is again mixed till it reaches the required consistency before using. Mud plasters made
of sand and clay can also be used.
Water proof plaster - This plaster consists of 1 part of cement, 2 parts of sand and pulverized alum at
the rate of 12 Kg/m^3 of sand. In order to make this to be water proof, soap water containing about
75 gm soap/liter of water is added.
Requirements of a good plaster
- It should not shrink while drying which results in cracking of the surface.
- It should adhere firmly to the surface and resist the effects of atmospheric agencies.
- It should provide the surface a decorative appearance and should durable.
- It should provide a smooth, non absorbent and washable surface.
- It should be economical with locally available materials.
- It should be highly workable.
- It should be possible to apply during all weather condition.
- It should be water tight or impermeable.
Tools for plastering

Trowel Float Floating Rule Spirit Level Plumb bob

Gauging trowel
 
Used for applying mortar on walls, mouldings, corners etc.

Float
  Used to spread mortar on surface and also for finishing

 
Made of thin tampered steel or wood

Floating rule
• To check the level of plastered surface
Plumb bob
• To ascertain verticality of plastered surface.
Miscellaneous tools
• Brushes, spirit level, set squares, straight edges etc.
Methods of Plastering
Plaster is usually applied in a single coat or double coat. Double coat plaster is applied where
thickness of plaster is required to be more than 15 mm or when it is required to get a very fine finish.
The process of applying a double coat cement plaster on wall surface consists of the following steps.

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Module IV Dept. of Civil Engineering, MEAEC
Step-1-Preparation of surface for plastering
Step-2-Ground work for plaster
Step-3-Applying first coat (or under coat or rendering coat)
Step-4-Applying second coat (or finishing coat or fine coat)
Step-1 (Preparation of Surface for Plastering)

 
Keep all the mortar joints of wall rough, so as to give a good bonding to hold plaster.
 Clean all the joints and surfaces of the wall with a wire brush, there should be no oil or grease
 etc. left on wall surface.
 If the surface is smooth or the wall to be plastered is old one, then rake out the mortar joint to a
 depth of at least 12 mm to give a better bonding to the plaster.
 If the projection on the wall surface is more than 12 mm, then knock it off, so as to obtain a
 uniform surface of wall. This will reduce the consumption of plaster.
 If there is any cavities or holes on the surface, then fill it in advance with appropriate material.
 
Roughen the entire wall to be plastered.
 Wash the mortar joints and entire wall to be plastered, and keep it wet for at least 6 hours
before applying cement plaster.
Step-2 (Ground Work for Plaster)
 In order to get uniform thickness of plastering throughout the wall surface, first fix dots on the
 wall. A dot means patch of plaster of size 15 mm * 15 mm and having thickness of about 10 mm.
 Dots are fixed on the wall first horizontally and then vertically at a distance of about 2 meters
 covering the entire wall surface.
  Check the verticality of dots, one over the other, by means of plumb-bob.
 After fixing dots, the vertical strips of plaster, known as screeds, are formed in between the dots.
These screeds serve as the gauges for maintaining even thickness of plastering being applied.
Step-3 (Applying First Coat or Under Coat or Rendering Coat)

 In case of brick masonry the thickness of first coat plaster is in general12 mm and in case of
 concrete masonry this thickness varies from 9 to 15 mm.
 
The ratio of cement and sand for first coat plaster varies from 1:3 to 1:6.
 Apply the first coat of plaster between the spaces formed by the screeds on the wall surface.
 This is done by means of trowel.
 
Level the surface by means of flat wooden floats and wooden straight edges.
 After leveling, left the first coat to set but not to dry and then roughen it with a scratching tool
to form a key to the second coat of plaster.
Step-4 (Applying Second Coat or Finishing Coat or Fine Coat)
 The thickness of second coat or finishing coat may vary between 2 to 3 mm.
 The ratio of cement and sand for second coat plaster varies from 1:4 to 1:6.
 Before applying the second coat, damp the first coat evenly.

 Apply the finishing coat with wooden floats to a true even surface and using a steel trowel, give
 it a finishing touch.
 As far as possible, the finishing coat should be applied starting from top towards bottom and
completed in one operation to eliminate joining marks.

After completion of the plastering work, it is kept wet by sprinkling water for at least 7 days in order
to develop strength and hardness.
Simple steps
1. All mortar joints of the wall are kept rough.
2. Clean the surface with a wire brush and made sure it is free from harmful substances like oil,
grease etc.
3. Projections more than 12mm knocked off to obtain uniform surface.

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Dept. of Civil Engineering, MEAEC Module IV
4. All holes and cavities are filled in advance and all woodwork surfaces to be plastered are
roughened.
5. The mortar joints and surfaces are washed and wetted and kept for 6 hours before
plastering.
6. To achieve uniform thickness for plastering, vertical strips formed on the wall surface by
fixing dots.
7. First coat of plastering is done.
8. If second coat is needed, it is done after 2 days curing of first coat.

POINTING
Final treatment with cement or lime mortar made to the joints of the masonry to provide neat
appearance is termed as pointing. The joint on the face of stone or brick masonry are roughly filled in
while the walls are being raised. They are after wards neatly finished off to make them water tight.
The joints thus finished, give a better appearance to surface and prevent rain water from entering the
interior of the masonry.
Purpose
 To prevent the moisture and the rain water from entering the interior of masonry through joints.
 To make them durable.
 To improve the appearance of the structure.
Suitability
Pointing is preferred to plastering under following conditions.
1. When a smooth and even surface is not essentially required.
2. Where it is desirable to exhibit to view the natural beauty of the materials (bricks or stones)
used in construction.
3. When the workmen ship is neat and good.
Types of pointing
The selection of particular type of pointing depends upon the types of bricks or stone used and the
appearance required.
1. Flat or flush pointing
In this pointing, the mortar is pressed tightly and the joints are filled up and made flush with the face
of the wall. This is the simplest type of pointing and is provided extensively. It is economical because
it requires less labor than all other pointing. It does not give good appearance, but it is durable as it
does not provide any space for accumulation of dust, water etc

2. Struck pointing
In this pointing the face of the mortar joint instead of keeping it vertical, its upper side is kept about
12 mm inside the face of the masonry and the bottom is kept flush with the face of the wall. This
pointing has a better effect of throwing rain water. This is also known as ruled pointing. This pointing
is the best in ordinary circumstances.
3. Recessed pointing
In this pointing the face of the mortar joint is pressed inside by means of a suitable tool and is left
vertical instead of being made inclined. This pointing is provided when face work of good textured
bricks with good quality mortar is used. Recessed joints are not suitable for buildings in exposed
situations because they do not readily shed water. Only bricks with good frost resistance should be
used with recessed joints. It Gives good appearance.

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Module IV Dept. of Civil Engineering, MEAEC
4. V-pointing
This type of pointing is provided by forming a v-shaped groove inside the mortar of the joint with a
special tool (steel or iron jointer). This pointing is commonly recommended for brick work in case of
governmental buildings.

5. Weather pointing
This is similar to V-Pointing but in this case instead of pressing a v shaped groove inside, it is provided
by forming a v shaped projection outside the wall’s surface. This pointing is generally recommended
for superior brick work.
6. Keyed or grooved pointing
In this case, the joints are first filled up flush, and then a circular piece
of steel or iron is pressed in and rubbed in the middle of joints.
Grooved pointing has a big groove in the face than keyed. Keyed
pointing gives an attractive appearance to the structure and is
generally used for superior work.
7. Tuck pointing
In this pointing, the mortar joints are filled with the face of the
wall. Then 6 mm wide and 3 mm deep groove is immediately and
carefully formed in the centre of the joint and the groove is filled
with or tucked in with white lime putty. The lime putty is given a
maximum projection of 6 mm. Tuck pointing has a neat attractive appearance. But the lime putty is
not durable and in due course of time becomes defective.
Method of pointing
 Raking of mortar joints at least 20mm depth
 Dust removed by brushes
 Surface washed out with clean water and kept wet for a few hours
 Mortar placed in these joints in desired shape using trowel

 Finished surface well-watered for at least 3 days for lime mortar and 10 days for
cement mortar

PAINTING
Paint is a fluid that spreads over a solid surface and forms a film when it dries. It is usually applied on
a surface in layers like primary coat, first coat, second coat etc.
Paints are applied on the surfaces of timber, metals and plastered surfaces as a protective layer and
at the same time to get pleasant appearance. Paints are applied in liquid form and after sometime
the volatile constituent evaporate and hardened coating acts as a protective layer.
Purpose
 Protect the surface of wood, metal and all structures from atmospheric influences.

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Dept. of Civil Engineering, MEAEC Module IV
 Prevent decay in wood
 Prevent corrosion in metal
 Provides clean ,smooth and colored surface
CONSTITUENTS OF PAINT
The essential constituents of paints are:
1. Base
2. A vehicle
3. A pigment
4. A drier and
5. A thinner.
1. Bases: It is a principal constituent of paint. It also possesses the binding properties. It forms an
opaque coating. Commonly used bases for paints are white lead, red lead, zinc oxide, iron oxide,
titanium white, aluminum powder and lithopone. A lead paint is suitable for painting iron and steel
works, as it sticks to them well. However it is affected by atmosphere action and hence should not be
used as final coat. While zinc forms good base but is costly. Lithophone, which is a mixture of zinc
sulphate and barytes, is cheap. It gives good appearance but is affected by day light. Hence it is used
for interior works only.
2. Vehicles: The vehicles are the liquid substances which hold the ingredients of paint in liquid
suspension and allow them to be applied evenly and uniformly on the surface to be painted. It
provides a binder for the ingredients of paint so that they may stick or adhere to the surface. Linseed
oil, Tung oil and Nut oil are used as vehicles in paints. Of the above four oils, linseed oil is very
commonly used vehicles. Boiling makes the oil thicker and darker. Linseed oil reacts with oxygen and
hardens by forming a thin film.
3. Pigment: Pigments give required colour for paints. They are fine particles and have a reinforcing
effect on thin film of the paint. The common pigments for different colours are:
Black—Lamp black, suit and charcoal black.
Red—venedion red, red lead and Indian red.
Brown—burned timber, raw and burned sienna
Green—chrome green, copper sulphate.
Blue—prussian blue and ultra marine
Yellow—ochre and chrome yellow.
4. The Drier: These are the compounds of metal like lead, manganese, cobalt. The function of a drier
is to absorb oxygen from the air and supply it to the vehicle for hardening. The drier should not be
added until the paint is about to be used. The excess drier is harmful because it destroys elasticity and
causes flaking.
5. The Thinner: It is known as solvent also. It makes paint thinner and hence increases the coverage. It
helps in spreading paint uniformly over the surface Turpentine and naphtha are commonly used
thinners. After paint applied, thinner evaporates and paint dries.
PROPERTIES OF AN IDEAL PAINT
1. It should be possible to apply easily and freely.
2. It should dry in reasonable time.
3. It should form hard and durable surface.
4. It should not be harmful to the health of workers.
5. It should not be easily affected by atmosphere.
6. It should possess attractive and pleasing appearance.
7. It should form a thin film of uniform nature i.e., it should not crack.
8. It should possess good spreading power.
9. It should be cheap.

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Module IV Dept. of Civil Engineering, MEAEC
TYPES OF PAINTS
Depending upon their constituents there are various types of paints. Brief descriptions of some of
them which are commonly used are given below:
1. Oil Paint: These paints are applied in three coats-primer, undercoat and finishing coat. The
presence of dampness while applying the primer adversely affects the life of oil paint. This paint is
cheap and easy to apply. It possesses good opacity and low gloss.
2. Enamel Paint: It contains white lead, oil, petroleum spirit and resinous material. The surface
provided by it resists acids, alkalies and water very well. It is desirable to apply a coat of titanium
white before the coat of enamel is applied. It can be used both for external and internal walls. It Dries
slowly and forms a hard durable surface. It is not affected by gases, acids, alkalies, hot water and cold
water, steam and temperature. It is available in different colours.
3. Emulsion Paint: It contains binding materials such as polyvinyl acetate, synthetic resins etc. It dries
in 1 to 2 hours and it is easy to apply.
The advantages of emulsion are:
1. This paint is easy to apply and dry within 2 hrs.
2. Possess good weather resistance and alkali resistance
3. Long lasting paint with no change in colour
4. It is possible to clean the painted surface with water
For long life of painting two coats of emulsion is applied. While applying emulsion paint on plastered
surface, apply a coat of cement paint to smoothen the plastered surface before applying emulsion
paint directly
4. Cement Paint: It is available in powder form. It consists of white cement, pigment and other
additives. It is durable and exhibits excellent decorative appearance. It should be applied on rough
surfaces rather than on smooth surfaces. It is applied in two coats. First coat is applied on wet surface
but free from excess water and allowed to dry for 24 hours. The second coat is then applied which
gives good appearance.
5. Bituminous Paints: This type of paint is manufactured by dissolving asphalt or vegetable bitumen
in oil or petroleum. It is black in colour. It is used for painting iron works under water.
6. Synthetic Rubber Paint: This paint is prepared from resins. It dries quickly and is little affected by
weather and sunlight. It resists chemical attack well. This paint may be applied even on fresh
concrete. Its cost is moderate and it can be applied easily.
7. Aluminium Paint: It contains finely ground aluminium in spirit or oil varnish. It is visible in darkness
also. The surfaces of iron and steel are protected well with this paint. It is widely used for painting gas
tanks, water pipes and oil tanks.
8. Anti-corrossive Paint: It consists essentially of oil, a strong dier, lead or zinc chrome and finely
ground sand. It is cheap and resists corrossion well. It is black in colour.
PROCESS OF PAINTING DIFFERENT SURFACES:
1. Painting on new wood work
The process of painting on new wood work can be divided into the following stages:
1. Preparation of surface: the surface of wood work is prepared to receive the paint. For
satisfactory working the woodwork should be sufficiently seasoned and the Moisture content of
timber must be less than 15% of their dry weight. The surface of woodwork should be thoroughly
cleaned and heads of nails are punched to a depth of 3mm below the surface.
2. Knotting
3. Priming: Pores get filled and opaque covering formed over the whole surface.
4. Stopping: Surface is rubbed with pumic stone
5. Surface coats or under coatings
6. Finishing coat

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 Dept. of Civil Engineering, MEAEC Module IV
Each coat applied only after previous coat has dried completely
2. Repainting on old wood work
Old paint should be completely removed
Removing old paint
1. Equal parts of washing soda and quick lime- mixture is brought to a paste form by adding
water
2. It is applied on the surface and kept for one hour, then washed off with water
3. After, wood surface is painted as that for new wood work.
3. Painting new iron and steel work
 Clean the surface by scrapping/brushing with steel wire brushes
 Phosphoric acid is used to remove the scale deposit on surface.
 Prime coat is applied using brush
  Two or more coats with a brush /spray gun
 Each coat applied only after previous coat has dried completely
4. Repainting old iron and steel work
 Before repainting, it should be thoroughly washed with soap water
 If grease is present it may be removed by lime water.

 Remove old paint by flat oxy-acetylene flame over the metal and then scrapped the surface with
 wire brush.
 Washed with solution of caustic soda and slaked lime.
5. Painting plastered surface
 For newly plastered wall, there is considerable amount of moisture.
 For applying paint wait for at least 3to 6 months.
  Defects in plastered surfaces are to be removed.
 Coats of alkali resistant primer paint should then be applied on the surface.
 Usual paints:- cement paint, silicate paint, emulsion paint

WHITEWASHING
Whitewash or lime paint is a low-cost type of paint made from slaked lime (calcium hydroxide,
Ca(OH)2) and chalk (calcium carbonate, (CaCO3), sometimes known as "whiting".
Preparation of White Wash
White wash is prepared from fat lime. The lime is slaked at the site and mixed and stirred with about
five liters of water for 1 kg of unslaked lime to make a thin cream. This should be allowed to stand for
a period of 24 hours, and then should be screened through a clean coarse cloth. One kg of gum is
dissolved in hot water may also be added for every 10 kg of lime. Sometimes, rice is used in the place
of gum. The application of sodium chloride (common salt) to lime-wash helps in quick carbonation of
calcium hydroxide making the coating hard and rub-resistant. Small quantity of ultra-marine blue (up
to 3 gm per kg of lime) may be added to the last two coats of white wash solution.
Preparation of Surface
The new surface should be thoroughly cleaned off all dirt, dust, mortar drops and other foreign matter
before white wash is to be applied. Old surfaces already white-washed or colour-washed should be
broomed to remove all dust and dirt. All loose scales of lime wash and other foreign matter should be
removed. Where heavy scaling has taken place, the entire surface should be scraped clean, any growth of
moulds moss should be removed by scrapping with steel scraper and ammonical copper solution
consisting of 15 gm of copper carbonate dissolved in 60 ml of liquor ammonia in 500 ml of water, should
be applied to the surface and allowed to dry thoroughly before applying white or colour wash.
Application of White Wash
White wash is applied with brush, to the specified number of coats (generally three). The operation in
each coat should consist of a stroke of the brush given from top down-wards, another from the bottom

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Module IV Dept. of Civil Engineering, MEAEC
upwards over the first before it dries. Each coat should be allowed to dry before the next coat is applied.
The white washing on ceiling should be down prior to that on walls.
The lime is toxic for germs. It reflects light and thus it increases the brightness of the surface. The
whitewashing therefore is extensively used for interior wall surfaces and ceilings of houses.
The process of whitewashing is sometimes used for exterior wall surfaces also. A satisfactory work
gives an opaque smooth surface with uniform white colour and does not readily come off on the
hand, when rubbed.

COLOUR WASHING
Colour washing is prepared by adding colouring pigment to the screened white wash. Generally used
pigments are yellow earth red ocher and blue vitriol. These are crushed to powder, before mixing.
The colour wash is applied in the same fashion as the white wash. For colour washing on new surface,
the first primary coat should be of white wash and the subsequent coats should be of colour wash. A
satisfactory work does not give out powder when the finished surface is rubbed with the fingers.The
process of colour washing imparts cleanliness and pleasant appearance of the surfaces which are
treated.

DISTEMPERING
Distempers are also called as water paints. It is prepared by mixing chalk and glue boiled in water.
Earthly pigments like ochre, umber, Indian red and lamb black also added to give colour shade to this
paint. They are also available in powder or paste form in that case to be mixed with water to form a
viscous fluid. Distempers are cheaper than paint and varnish. These paints are used for painting
interior walls. The main use of applying distemper to plastered surface is to give a smooth outer
surface in low cost. Distemper is porous. It Allows water vapor to escape. It is less durable.
The main object of applying distemper to the plastered surfaces is to create a smooth surface. The
distempers are available in the market under different trade names. They are cheaper than paints
and varnishes and they a present a neat appearance. They are available in a variety of colours.
Properties of distempers:
Following are the properties of distempers:
 On drying, the film of distemper shrinks. Hence it leads to cracking and flaking, if the surface to
 receive distemper is weak.
 The coatings of distemper are usually thick and they are more brittle than other types of water
 paints.
 The film developed by distemper is porous in character and it allows water vapour to pass
 through it. Hence it permits new walls to dry out without damaging the distemper film.
 They are generally light I colour and they provide a good reflective coating.
 They are less durable than oil paints.
 They are treated as water paints and they are easy to apply.

 They can be applied on brickwork, cement plastered surface, lime plastered surface, insulating
 boards, etc.
  They exhibit poor workability.
 They prove to be unsatisfactory n damp locations such as kitchen, bathroom, etc.
Ingredients of a distemper:
A distemper is composed of base, carrier, colouring pigments and size. For base, the whiting or chalk
is used and for carrier, the water is used. Thus it is more or less a paint in which whiting or chalk is
used as base instead of whit lead and the water is used as carrier instead of linseed oil.
The distempers are available I powder form or paste form. They are to be mixed with hot water
before use. The oil-bound distempers are a variety of an oil paint in which the drying oil is so treated
that it mixes with water. The emulsifying agent which is commonly used is glue or casein. As the
water dries, the oil makes a hard surface which is washable.

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 Dept. of Civil Engineering, MEAEC Module IV
It should be remembered that most of the manufacturers of readymade distempers supply completely
directions for use of their products. These directions are to be strictly followed to achieve good results.
Process of distempering:
The application of distemper is carried out in the following way:
Preparation of surface: The surface to receive the distemper is thoroughly rubbed and cleaned
Preparation of New Surface
 Newly plastered surfaces are allowed to dry for at least two months before the application of
 distemper.
 The surface is brushed thoroughly to make it free from mortar droppings.
 Then the sand paper is rubbed to make the surface smooth.
Preparation of Old Surface
 All loose pieces and scales are removed by sand papering.
  The surface is cleaned of all grease, dirt, etc
 Holes in plaster are filled in with Plaster of Paris mixed with color.
 Then the surface is rubbed down again with fine grade sand paper to make it smooth.
 A coat of distemper is applied on patches.
 The patched surface is allowed to dry thoroughly before applying regular coat of distemper.
Priming Coat
A priming coat of approved primer is applied over prepared surface in case of new work. No white
washing coat is used as priming coat for distemper. The treated surface is allowed to dry before
applying distemper coat.
Application on New Construction
After the application of primary coat two or more coat of distemper should be applied till the surface
shows an even color.
Application on Old Work
One or more coats of distemper should be applied on the surface till the surface attains an even color.
Procedure of Application
 The entire surface should be coated with proper distemper brushes in horizontal strokes
 uniformly followed by vertical ones immediately.
 The subsequent coats should be applied only after the previous coats are dried.
 The finished surface should be even and uniform showing no brush marks.
  Enough distemper should be mixed to finish one room at a time.
 After a days work the brushes should be washed in hot water and hung down to dry.
 Old and dirty brushes with distemper should not be used.
Precautions during Distempering
 Doors, windows, floors and electrical items should be protected from the splashes of
 distemper.
 If any drops of distemper fall on any articles, these should be cleaned immediately.

 After distempering care should be taken that the surface is not destroyed by touching with
any dirty materials.

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Module IV Dept. of Civil Engineering, MEAEC

DAMP PROOF COURSE (DPC)

Properties of Materials for DPC
An effective damp proofing material should have the following properties;

  It should be impervious.
 It should be strong and durable, and should be capable of withstanding both dead as well
 as live loads without damage.
 It should be dimensionally stable.
 It should be free from deliquescent salts like sulphates, chlorides and nitrates.
Types of Materials for Damp Proof Course
The materials commonly used to check dampness can be divided into the following three categories:
 Flexible Materials: Materials like bitumen felts (which may be hessian based or fiber/glass
 fiber based), plastic sheeting (polythene sheets) etc.
 Semi-rigid Materials: Materials like mastic, asphalt, or combination of materials or layers.
 Rigid Materials: Materials like first class bricks, stones, slate, cement concrete etc.
Selection of Materials for Damp Proof Course in Buildings
The choice of material to function as an effective
damp proof course requires a judicious selection.
It depends upon the climate and atmospheric
conditions, nature of structure and the situation
where DPC is to be provided
The points to be kept in view while making
selection of DPC materials are briefly discussed
below:

1. DPC above ground level

For DPC above ground level with wall thickness generally not exceeding 40 cm, any one of the type of
materials mentioned above may be used. Cement concrete is however commonly adopted material
for DPC at plinth level, 38 to 50mm thick layer of cement concrete M15 (1:2:4 mix) serves the
purpose under normal conditions.
In case of damp and humid atmosphere, richer mix of concrete should be used. The concrete is
further made dense by adding water proofing materials like Pudlo, Impermo, Waterlock etc. in its
ingredients during the process of mixing. It is used to apply two coats of hot bitumen over the third
surface of the concrete DPC.
2. DPC Material for floors, roofs etc.
For greater wall thickness or where DPC is to be laid over large areas such as floors, roofs, etc., the
choice is limited to flexible materials which provide lesser number of joints like mastic, asphalt,
bitumen felts, plastic sheets etc.
The felts when used should be properly bonded to the surface with bitumen and laid with joints
properly lapped and sealed.
3. DPC Material for situations where differential thermal movements occur
In parapet walls and other such situations, materials like mastic, asphalt, bitumen felts and metal
(copper or lead) are recommended.
It is important to ensure that the DPC material is flexible so as to avoid any damage or puncture of
the material due to differential thermal movement between the material of the roof and the parapet.

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 Dept. of Civil Engineering, MEAEC Module IV
4. DPC material for Cavity Walls
In cavity wall construction, like cavity over the door or window should be bridged by flexible material
like bitumen felt, strips or lead etc.
General principles to be observed while laying damp proof course are:
1. The DPC should cover full thickness of walls excluding rendering.
2. The mortar bed upon which the DPC is to be laid should be made level, even and free from
projections. Uneven base is likely to cause damage to DPC.
3. When a horizontal DPC is to be continued up a vertical face a cement concrete fillet 75mm in
radius should be provided at the junction prior to the treatment.
4. Each DPC should be placed in correct relation to other DPC so as to ensure complete and
continuous barrier to the passage of water from floors, walls or roof.
METHODS OF PROVIDING DPC
1. Membrane damp proofing
In this method of damp proofing a water repellent membrane or damp proof course(D.P.C.) is introduced
in between the source of dampness and the part of building adjacent to it. Damp proofing course may
consist of flexible materials such as bitumen, mastic asphalt, bituminous felts, plastic or polythene sheets,
metal sheets, cement concrete. Damp proofing course may be provided either horizontally or vertically in
floors, walls etc. Provision of Damp Proofing Course in basement is normally termed as ‘Tanking’. The
general principles to be followed while providing damp proof course are:

  The damp proofing course should cover the full thickness of walls, excluding rendering.
The mortar bed supporting damp proof course should be leveled and even, and should be
free from projections, so that damp proof course is not damaged.
  Damp proof course should be laid in such a way that a continuous projection is provided.
 At junctions and corners of walls, the horizontal damp proof course should be laid
 continuous.
When a horizontal damp proof course (i.e. that of a floor) is continued to a vertical face, a
cement concrete fillet of 7.5 cm radius should be provided at the junction.
Each damp proof course should be placed in correct relation to other damp proof course,
so as to ensure a complete and continuous barrier to the passage of water from floors,
walls or roof.
 Damp proof course should not be kept exposed on the wall surface otherwise it may get
damaged during finishing work.

2. Integral damp proofing

In the integral damp proofing method certain water proofing compounds are added to the concrete
mix, so that it becomes impermeable. The common water proofing compounds may be in the
following three forms.
 Compounds made from chalk, talc, fullers earth, which may fill the voids of concrete
 under the mechanical action principle.
Compounds like alkaline silicates, aluminum sulphate, calcium chlorides, etc. which react
chemically with concrete to produce water proof concrete.
Compounds like soap, petroleum, oils, fatty acid compounds such as stearates of calcium,
sodium, ammonia etc. work on water repulsion principle. When these are mixed with
concrete, the concrete becomes water repellent.
 Commercially available compounds like Publo, Permo, and Silka etc.

The quantity of water proofing compound to be added to cement depends upon the manufacturer’s
recommendations. In general one kilogram of water proofing compound is added with one bag of
cement to render the mortar or concrete waterproof.

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Module IV Dept. of Civil Engineering, MEAEC
3. Surface treatment
Moisture finds its way through the pores of material used in finishing. In order to check the entry of
the moisture into the pores, they must be filled up. In the surface treatment method a layer of water
repellent substances or compounds are applied on these surfaces through which moisture enters.
The use of water repellent metallic soaps such as calcium and aluminum oletes and stearates are
much effective against rain water penetration. Pointing and plastering of the exposed surfaces must
be done carefully, using water proofing agents like sodium or potassium silicates, aluminum or zinc
sulphates, barium hydroxide and magnesium sulphates etc. Surface treatment is effective only when
the moisture is superficial and is not under pressure. Sometimes, exposed stone or brick wall face
may be sprayed with water repellent solutions. The walls plastered with cement, lime and sand
mixed in proportions of 1:1:6 is found to serve the purpose of preventing dampness in wall due to
rain effectively.
4. Cavity wall construction
Cavity wall construction is an effective method of damp prevention. In this method the main wall of a
building is shielded by an outer skin wall, leaving a cavity between the two. The cavity prevents the
moisture from travelling from the outer to the inner wall.
5. Guniting
In this method of damp proofing, an impervious layer of rich cement mortar is deposited under
pressure over the exposed surfaces for water proofing or over pipes, cisterns etc. for resisting the
water pressure. The operation is carried out by use of a machine known as cement gun. The cement
gun consists of a machine having arrangements for mixing materials and a compressor for forcing the
mixture under pressure through a 50 mm dia flexible hose pipe. The hose pipe has nozzle at its free
end to which water is supplied under pressure through a separate connection.
The surface to be treated is first thoroughly cleaned of dirt, dust, grease or loose particles and wetted
properly. Cement mortar consists of 1: 3 cement sand mix, is shot on the cleaned surface with the
help of a cement gun, under a pressure of 2 to 3 kg/cm2. The nozzle of the machine is kept at a
distance about 75 to 90 cm from the surface to be gunited. The mortar mix of desired consistency
and thickness can be deposited to get an impervious layer. The layer should be properly cured at
least for 10 days. Since the material is applied under pressure, it ensures dense compaction and
better adhesion of the rich cement mortar and hence the treated surface becomes water proof.
6. Pressure grouting
This consists of forcing cement grout under pressure, into cracks, voids, fissures and so on present in
the structural components of the building, or in the ground. Thus the structural components and the
foundations which are liable to moisture penetration are consolidated and are thus made water-
penetration-resistant. This method is quite effective in checking the seepage of raised ground water
through foundations and sub-structure of a building:

*******************************
Prepared By
NAJEEB. M
Assistant Professor
Dept. of Civil Engineering
MEA Engineering College

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Dept. of Civil Engineering, MEAEC Module IV

LINTELS
• Introduction
• Classification of lintels
ARCHES
• Arches : Terms to be used
• Stability of an arch
• Classification of an arches

1 2

Introduction
™A lintel is defined as a horizontal
structural member which is placed across
the opening.

33 4

Classification of lintel Timber lintels

Lintels are classified into the following ™Easily available in hilly area.
types, according to the materials of their
construction: ™Relatively costly, structurally weak
™[1] Timber lintels and valnerable to fire.
™[2] Stone lintels ™Easily decay, if not properly taken care.
™[3] Brick lintels TIMBER LINTEL
™[4] Reinforced Brick lintels
™[5] Steel lintels
™[6] Reinforced cement concrete lintels
5

66

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Module IV Dept. of Civil Engineering, MEAEC

Stone lintels
™Used , where stones
Stone lintels
are easily available.
™Consists of a
simple stone slab
of greater
thickness.
™Due to high cost and
its inability to with
stand the vibratory
load.
7 88

STONE LINTEL

Brick lintels Reinforced Brick lintels

™The brick are BRICK LINTEL
™For large spans
hard, well burnt and heavy loads .
, first class bricks
™They are reinforced
™Not
with mild steel bars.
structurally
™Very common due to
strong
durability, strength
™Suitable for
small span. and fire resisting
™The bricks properties.
having frogs are ™Joints are filled
more suitable. 9 with cement
concrete.
10

Steel lintels REINFORCED CEMENT CONCRETE LINTEL

™Provided at large
opening and where the
super-imposed loads ar e
heavy.
™Common in used.
™It consists of rolled ™They may be R.C.C. LINTEL

steel joists . pre-

™Either used singly or in cast .
combination of two or ROLLED STEEL JOIST three ™For smaller span,
units. the pre-cast
concrete lintels
™Joint with bolts. are used.
™Depth of lintel
11
depend on 12122

span.
4.42 | Page CE 204 – Construction Technology
 Dept. of Civil Engineering, MEAEC Module IV

ARCHES
ƒ The structure
constructed of wedge
shaped block of stones
or bricks ,jointed
together with mortar and
provided across the
opening to carry the
weight of the structure
above the opening.

13 1414

15 ELEMENTS OF ARCHES 16

TECHNICAL TERMS 3)Intrados :-This is the inner curve or surface of

The various technical terms used in arches are an arch.
as follows:- 4)Extrados :-This is the outer curve or surface of
1)Abutment:-This is the end support of an arches. the arches.
2)Pier:-This is support an intermediate of an arch. 5)Voussoirs :-The voussoirs or arch stones are
the wedge shaped units forming the arch.

1717 18188

CE 204 – Construction Technology 4.43 | Page

Module IV Dept. of Civil Engineering, MEAEC

6)Springing stone:-The springing stone or

springer is the first voussoir at springing level
on either side of the arches.
7)Springing line:-This is an imaginary line
joining the two springing points.
8)Crown:-This is the highest point of extrados
or it is the highest part of an arches.

19 20

11)Span:-This is the clear horizontal distance between the

9)Keystone:-This is the highest central wedge two supports.
shaped block of an arch. 12)Rise:-this is the vertical distance between the two
supports.

10)Skew back:-This the surface of the abutment

on which the arch rests. 21
13)Depth of arch:-This is the perpendicular distance
between
the intrados and extrados. 22

14)Haunch of an arch:-This is the portion of

arch situated centrally between the key and
skew backs.
15)Spandril:-This is the triangular walling enclosed
by the extrados of the arch, a horizontal line
from the crown of the arch and perpendicular
line from the springing of the outer curves.

23 24

4.44 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module IV

™EVERY ELEMENT OF ARCH REMAINS IN

COMPRESSION.
™An arches fail due to:-
1)Crushing of the masonry.
2)Sliding of voussoirs.
3)Rotation of some joints about an edge.
4)Uneven settlement of an abutment or pier.

25 26

Classification of arches CLASSIFICATION BASED ON MATERIAL AND

WORKMANSHIP
An arch may be classified according ¾ BRICK ARCHES
to their: *Rough brick arches
1)Material of construction and workmanship *Axed brick arches
2)Shape of curve formed by their soffit *Gauged brick
or intrados arches
¾ STONE ARCHES
3)Number of centers. *Rubble
arches *Ashlar
arches
27 ¾ GAUGED ARCHES
*Precast concrete block arches
*Monolithic concrete arches 28

ROUGH BRICK ARCHES AXED BRICK ARCHES

฀ These arches are built ฀ Bricks are cut to
with ordinary bricks, which wedge-shape.
are not in wedge shape . ฀ Joints of arches
฀ Also known as are of uniform
“RELIEVING ARCHES”. thickness.
™Made up of rectangular ฀ Not dress finely so it
brick that are not cut into does not give much
wedge shape. Curvature attractive appearance.
are obtained by mortar.

29 30

CE 204 – Construction Technology 4.45 | Page

Module IV Dept. of Civil Engineering, MEAEC

GAUGED BRICK ARCHES RUBBLE ARCHES

฀ Accurately prepared to wedge shape. ฀ Made of rubble stones, which are
hammer dressed, roughly to the shape and size
฀ Specially shaped bricks known as of voussoirs of the arch and fixed in cement
“RUBBER BRICKS” are used .(soft mortar.
bricks)
฀ These arches are used for small span upto
฀ The lime putty is used for binding the blocks. 1 m.

3131 3232

ASHLAR ARCHES PRECAST CONCRETE BLOCK ARCHES

฀ Stones are cut to ฀ Used
proper shape of voussoirs for small
and are fully dressed, openings in
properly joint with building.
cement or lime. ฀ The
฀ The voussoirs voussoirs, in the
form of cement
made of full thickness of concrete blocks are
the arch. prepared in special
moulds .
฀ Generally
, the concrete
blocks are used
without
reinforcement.
3333 34

Types Of Arches on Material of Construction

MONOLITHIC CONCRETE ARCHES
฀ Constructed from
cast-in-situ concrete
,either plain or
reinforced , depending
upon the span and
magnitude of loading. Rubble Arch AshlarArch Monolithic Concrete Arch

฀ Quit suitable for

larger span (3.0 m).
฀ The curing is
done 2 to 4 weeks.

R.C.C Arch Metal Arch Wooden Arch

35 HRISHIRAJ SARMA | A.P.I.E.D | 2014 36

4.46 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module IV

FLAT ARCH
Classification according to shape
฀ Acts like a lintel,
when it provided
¾Flat arch over the opening .
¾Segmental arch ฀ Joints radiated
to center.
¾Semi-circular arch
฀ Used only
¾Relieving arch for light loads
¾Dutch or French arch only.
฀ Span up to 1.50 m.

37 3838

SEGMENTAL ARCH SEMI-CIRCULAR ARCH

฀ The shape of the curve given to the arch
฀ Segmental in soffit is semi-circular.
shape and provided
over the openings . ฀ The center of the arch lies on the
฀ Joints radiate springing line.
from a center of arch,
which lies below the
springing line.

3939 4040

SEMI-CIRCULAR ARCH RELIEVING ARCH

ƒ When wooden lintel is
provided over the
wider opening, a
brick relieving arch
is constructed above
the lintel.
ƒ Relieving the load of
masonry over lintel.

41 4242

CE 204 – Construction Technology 4.47 | Page

Module IV Dept. of Civil Engineering, MEAEC

Dutch or French arch Types of Arches on Geometry

• A flat arch in brick; most of the bricks slope

ou tward from the middle of the arch (at the
sam e angle on both sides of the centerline)
Flat Arch French of Dutch Arch

Segmental Arch
43 Semi circular Arch HRISHIRAJ SARMA | A.P.I.E.D | 2014 44

CLASSIFICATION BASED ON NUMBER OF

CENTRES

฀ One centred arch.

฀ Two centred arch.
฀ Three centred arch.
฀Four centred
arch.
฀ Relieving Arch
฀ Five centred arch.

45 46

ONE CENTRED ARCH TWO CENTRED ARCH

฀ Segmental, semi circular, flat arches ฀ Pointed, semi-elliptical arches
come under this category. come under this category.
฀ Sometime , a perfectly circular arch
known as bull’s eye arch ,provided for
circular window.

4747 48

4.48 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module IV

THREE CENTRED ARCH FOUR CENTRED ARCH

฀ It has four center.

ƒ Elliptical arches
come under this O2
O3
฀ Venetian arch is
category. typical example of this
ƒ O1,O2 and O3 type.
O1
are the center.

49 50

FIVE CENTRED ARCH

฀ This type of arch ,having five

centre's ,gives good semi-elliptical shape.

51

CE 204 – Construction Technology 4.49 | Page

Module IV Dept. of Civil Engineering, MEAEC

 Termite control in building is very important

as the damage likely to be caused by the
 termite is huge.
 Termites damages the cellulosic materials
(Like wood) at faster rate because cellulose
forms their nutrients .
 Termites also known to damage non
cellulosic material in their search for food .

According to their habits, termites are Termite damage indoors on walls

classified into two well defined groups:-
 Subterranean :-
Termite nest on walls
Termites which builds their nests in the soil.
 Non Subterranean (dry wood):-
These type of termites are wood nesting ,which
live in wood with no contact to soil.

 Pre-construction anti-termite treatment is

considered as most effective way to prevent
termite invasion in buildings or homes.

 In this soil under the foundation is treated
with chemicals. A chemical barrier is formed
Termite between ground and brickwork of the
holes on foundation to avoid termites access to the
building.
wood

Termite destruction of wooden Doors

4.50 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module IV

 Post construction anti-termite treatment is 1. Pre construction

conducted after the completion of the
construction of the building. This normally 2. Post construction
consists of re-using termiticides to the soil
around the foundation. Also treat the floors
of the rooms by making holes under floors
and fill them with chemicals for Termite
Control.

 The various operation involved in this  The site preparation consist of removing the
 treatment are as follows stumps, roots, logs, waste woods etc from
I. Site preparation the site where the building is to be
II. Soil treatment  constructed.
 If the termite mounds are detected within the
III. Structure barriers
plinth area of the building they should be
destroyed by the use of insecticide solution.

 To make the soil treatment effective the CHEMICAL CONCENTRATION BY WEIGHT

chemical water emulation is applied in Aldrin 0.5%

Heptachlor 0.5%
required dosage on entire area of ground
Chlordane 1%
covered by the building.

 The watering can or and operated compressed
air sprayer can be used to ensure distribution
of the chemical emulsion.

CE 204 – Construction Technology 4.51 | Page

Module IV Dept. of Civil Engineering, MEAEC

Schematic diagram of Pre-

Pre-construction anti-termite treatment
construction anti-termite
treatment

 This treatment is applied to existing buildings which are

 The structure barriars may be provided  already attacked by termites.
continually at plinth level to prevent entries  The termites even after their entries in the building they
 of termites through walls. maintain regularly contact with their nest in the ground. 

 The cement concrete layer 5 to 7.5 cm thick
 In case of sever attack the soil around and beneath
may be provided projecting 5 to 7.5 cm on

the building is treated with chemical emulsion.
both the side.
 The wood work which is badly damaged by termites may
 The metal barriers consist of non corrodible be replaced by new timber brushed with oil or kerosene
sheets of copper or galvanized iron of 0.8 based chemical emulsion.
 The wood work which is not attack by termites
mm thick may be provided on both the side.
may be sprayed over with chemical emulsion to
prevent the possible attack .

Drilling for Post construction anti-termite treatment

4.52 | Page CE 204 – Construction Technology

MODULE 5
 Dept. of Civil Engineering, MEAEC Module V
MODULE 5
Syllabus:
Tall Buildings – Framed building – steel and concrete frame – structural systems –erection of steel
work–concrete framed construction– formwork – construction and expansion joints Introduction to
prefabricated construction – slip form construction Vertical transportation: Stairs – types - layout and
planning-
Elevators – types – terminology – passenger, service and goods elevators – handling capacity -
arrangement and positioning of lifts – Escalators – features –use of ramps.

TALL BUILDINGS
The modern history of tall buildings began with the introduction of wrought and cast iron into the
construction industry in the eighteenth century. High speed elevators, reliable foundations, heating
th
and ventilation systems led to the construction of high rise structures in the early to mid-20
century. R.C.C began to be used in the construction of tall buildings in 1960s. The potential of new
building methods such as space frame technology and composite construction may change the shape
of tomorrow’s buildings.
Advantages of Tall Buildings
 Land use economy: Multi- storied buildings results in large buildings getting concentrated on
 relatively small built up area.
 Large proportion of open space for creating natural environment.
 Better day lighting.
 Greater airflow.
  Freedom from air noise.
 Panoramic view of the city.
Problems of Tall Buildings

 Steps should be taken to prevent excessive and imbalanced load on municipal services like
 water supply, sewerage, electricity.
 Accidental fire hazards and earthquake disasters.
  Traffic hazards.
 Parking difficulties.
 Congestion of area

 Social and human problems. This arises out of the social and economic background of the
 population and also the indigenous conditions of living like climate.
 The density of population going out of control.
Design of Tall Buildings
 Design of tall buildings is dominated by resistance to horizontal forces.
  In addition to structural safety, sway limitations should be satisfied.
 In low to medium-rise buildings the structured system is designed primarily to resist the
vertical loads and is then checked for lateral forces. In this case lateral forces can be by frame
 action by braced frames or by shear walls.
 But greater magnitudes of forces and movements necessitates a more sophisticated
approach in such cases structured frame has to be specially designed to withstand heavy
 loads and wind pressure and earthquakes shocks.
 Installing semi dampers like viscous dampers friction dampers and yielding dampers in place
 of structural elements like diagonal braes can reduce earthquakes effects in building.
 Research is in progress to develop highly damped partition wall system which can be
provided in core areas for the full building height. This can also serve as fire resistant
enclosures.

CE 204 – Construction Technology 5.1 | Page

Module V Dept. of Civil Engineering, MEAEC
 Research is also in progress to develop a building material which would increase building
damping and at the same time increase the fire resistance of structural steel members.
 Such materials can be glued or sprayed to all primary structural members.
 Planning and layout of tall multi-storey buildings require special attention in orientation of
buildings with respect to prevailing wind direction and sunrays. Provision of adequate open
space for gardens and lawns around the building. Suitable arrangements for parking, traffic,
drainage, etc. should be provided.
The general trend in India for planning the space requirement is
 Total build up - 30 to 40 %land area.
 Carpet area - 55 to 66% of plinth occupation area.
 Extend walls and columns - 4 to 6% plinth area.
 Extend walls and partitions - 3 to 7% of plinth area.
 Area of horizontal circulation - 12 16%of plinth area.
 Entrance and lobbies - 2 to 4%of plinth area.
 Windows - 9 to 12% of plinth area.
 Area of vertical circulation consisting of lifts and staircase - 6 to 8% of plinth area.
 Area of toilets - 3 to 4% of plinth area.

CONCEPT OF FRAMED STRUCTURES

Framed structures are comprised of series of frames. These frames are formed of columns which are
connected by means of beams at floors and roofs levels. Within these frames walls are constructed.
In the case of framed structures the loads of floors, roofs and panel walls are supported by beams
which transmit these loads to the columns. Columns transmit the loads to foundation. Walls can
be cast in situ or pre cast walls or it can even be cladding (thin sheets used to enclose frames).
TIMBER FRAMED BUILDINGS
Framed structures offer advantages like beauty, low thermal inductance, electrical insulation,
high shock absorption capacity length strength at low temperature.
When wooden frames are used, the walls are conventionally built -with slender studs spaced 40cm
c/c. Similarly joists and rafters which are supported on the walls and partitions are also spaced 40cm
c/c.
Facing such as sheathing, wall board etc is attached to joists and rafters.

  They are stronger and more durable.

 Experience has shown that living in houses that consist largely of wood offer people
 health benefits.
 According to research, wood also has a positive psychological effect.

 It is rapidly erected… an “average”-sized timber-frame home can be erected within 2 to 3
 days.
 There are a limited number of load bearing walls in a timber frame structures, allowing more
 flexibility and changes to the floor plan.
 The generally larger spaces between the frames enable greater flexibility in placing and re-
locating windows and doors during and after construction, with less concern over structural
 implications and the need for heavy lintels.
  The working structure of the array can be seen, studied, and enjoyed.
 Use of sustainable materials, such as local wood, contributes to a lower carbon footprint and
 lower cost to the environment.
 A very low carbon footprint is created when local woods are used.
 The building process creates almost no waste.
  Timber waste can be recycled.
 It can use recycled or otherwise discarded timbers

5.2 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module V
Potential Problems with Timber Frame Construction
 Additional design and engineering time
 Lack of experienced builders and erection crews
  Low fire resistance
 Susceptibility to decay of timber when exposed to excessive moisture
 Susceptible to failure during transportation and placing
STEEL FRAMED BUILDING
In the case of multistoried buildings, commonly used material is mild steel. Cast iron is strong in
compression and wrought iron is strong in tension. But, mild steel is strong both in tension and
compression.
  
In this case beams, girders (build up section) and columns are made up of steel sections.
 
 These buildings should be adequately braced in order to resist the wind and earthquake forces.

Fire proofand other light materials are generally used for the partitions and exterior walls of these
 buildings.

  Therefore it will take less
Steel being much stronger is capable of sustaining greater load in a given space.
floor area to perform its function (slender and thinner sections are possible).
 
 For economy members subjected to bending should be as deep as possible in the direction of the max .B.M.
 
Skew frames, eccentric loading, circular or curved work must be avoided as far as possible.

Rolled structural steel sections

The steel sections manufactured in rolling mills and used as structural members are known as rolled
structural steel sections.
Various types of rolled structural steel sections.
1. Rolled steel I sections or H sections: These are employed to resist bonding. Used as
independent sections to resist axial forces (compression or tension). Also used in built up
sections of columns.
I section Sizes 7.5cm x 5cm at 6.1kg to 60cm x 21cm at 99.5kg. H section 15cm x 15cm at 27.1
kg to 45cm x 25cm at 92.5 kg.
2. Rolled steel channel sections: They consist of two equal angles. Used to resist bending (e.g.:
as purlins in the rolling of industrial building). These members are subjected to torsion
because of the unsymmetry of the section. These sections are also used as members
subjected to axial compression (in the shape of built up section). Used in steel framed
structures, girders, etc.. The channel section is available in sizes 10cm x 4.5cm to 4cm x 10cm.
Used in beams, columns, girders and roof truss, etc.
3. T Sections: Used to transmit bracket loads to columns. Also used with flat strips to connect
plates in the steel rectangular tanks. Size 2cm x 2cm with 3mm thickness to 15cm x 15cm
with 10mm thickness. Used in built up construction & steel roof trusses.
4. Angle sections: there are two types. Equal angle and unequal angle. Angles having equal
arms are called equal angles. Angles having unequal arms are called unequal angles. The sizes
and thickness of the angles are specified in the IS Code (IS800). The equal angles are available
in sizes 2cm x 2cm to 20cm x 20cm and thickness vary from 2mm to 25mm. For unequal angle
sizes 3cm x 2cm to 20cm x 15cm. t=5mm to 18mm.
Angles are used in steel framed buildings and steel roof trusses.
Uses:
a) To resist axial forces and transverse forces.
b) As connecting elements in build-up sections.
c) For connecting beams to columns.
d) Used in steel roof trusses, filler, joint floors, etc.

CE 204 – Construction Technology 5.3 | Page

Module V Dept. of Civil Engineering, MEAEC
5. Plates – wider sections of flat bars usually of width more than 500mm and thickness varying
from 5 to 50mm used in the construction of beams and columns.
6. Round bars – 5mm to 30mm. Round bars are circular in cross section, usually used for RCC
construction and also for trusses.
7. Square bars – having a dimension of 5mm to 30mm.Used in steel grill work, window, gate, etc.
8. Flat bars – 500mm used in steel grill work of windows, gate, etc. 5mm to 25mm.
9. Ribbed tor steel bars (HYSD bars): HYSD – High Yield Strength Deformed. Yield strength –
500N/mm2 (old twisted deformed bars from high strength steel).
Advantages of HYSD:

HYSD has strength of 1.5 to 2 times of
mild steel in compression as well as tension whereas its cost
 is only 10% more than the mild steel.


Because of higher strength ribbedsteel bars of smaller diameter are used which require less RCC
section for beams, columns, etc.

  of for steel bars exhibit excellent bonding property and hence it
Ribs or projections on the surfaces
can be used without end hooks.
 
 No extra lap length over that for mild steel is required even when no end hoods are provided.
 0
 It is possible to bend through 180 
without cracks and is also possible to weld them by electric
flesh but welding and are welding.
 
Labour charges are saved due to simplicity in bending, fixing and handling of bars.

Figures of structural steel sections

Erection of steel work
1. Collecting the section from shop.
2. Stacking the material at site
3. Establishing that the foundations are suitable and safe for erection to commence.
4. Lifting and placing the member: Lifting and placing components into position, generally using
cranes but sometimes by jacking. To secure components in place bolted connections will be
made, but will not yet be fully tightened.
5. Temporary bracing system to ensure stability during erection.
6. Aligning and permanently connecting the members by bolting , riveting or welding :Aligning
the structure, principally by checking that column bases are lined and level and columns are
plumb. Packing in beam-to-column connections may need to be changed to allow column
plumb to be adjusted. Bolting-up which means completing all the bolted connections to
secure and impart rigidity to the frame.
7. Application of final coat of painting.

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Dept. of Civil Engineering, MEAEC Module V
General principles in the design of steel framed construction:
1. Use of standard steel sections.
2. Steel should be selected to give higher strength. Materials with bigger modules of section
should be preferred.
3. The members subjected to bending stress or flexural stresses should be deepest in the
direction of maximum BM.
4. Joints should be rigid.
5. Joints should be properly made considering the difficulties of transport, and erection.
Subsequent painting work should be done. The use of curved or circular work should be
avoided as far as possible.
6. Columns supporting the upper floor loads should start from the basement.
7. Skew framing and eccentric loading should be avoided.
8. For the economy, appearance and simplicity in erection, it is advisable to provide equal space
for columns.
9. Riveting work should be arranged in workshop. (field driven rivets will not be efficient)
10. While erecting a building, ensure that only the design load is carried by the steel work
Methods of connecting steel structures
The members of steel structures are required to be connected for the transfer of the load safely.
These connections are as follows.
1. Bolt connections
2. Riveting connections
3. Welding connections
1. Bolt connections
It consists of bolts, nuts and washers. These are usually used for temporary joining of structural
members of steel framed structures. For making bolt connections, holes are made in the member
with diameter 0.5mm larger than the external diameter of the bolt.
Advantages:
  
No noise is produced.
  
No requirement of skilled labour.
  
No fire hazard.
 
 Changes of connection or altering of structure is simple.

2. Riveting
A piece of round steel forged in place to connect two or more than two structural members
together is known as a rivet. The rivets for structural purposes are manufactured from mild steel
and high tensile steel bars. A rivet consists of a head and a body. The body of the rivet is termed
as shank. The rivets are manufactured in different lengths. Heated rivets of different shapes of
head when inserted in the holes form another head on the other side by means of pneumatic
hydraulic hammer or riveter. Holes for riveting may be drilled, bored or punched. But the drilled
holes are generally preferred.
Two common methods of rivet connection are:
(i) Lap joint: the connected plates are lapped one over the other and riveted.
(ii) Butt joint: plates are connected with the aid of additional covering plates on one or
both the sides. Rivets are arranged in one or more rows.

CE 204 – Construction Technology 5.5 | Page

Module V Dept. of Civil Engineering, MEAEC

Lap Joint

Butt Joint
3. Welding
Welding method connecting the various members of a steel framed structure has proved to be
most effective. There are various types of welding connections: lap type, butt type and filler
connections are commonly used. The common methods are electric arc method and oxy
acetylene gas welding. For structural work, electric arc welding is used and for cutting steel, oxy
acetylene gas welding is used. In both the methods, the principle of welding lies in melting both
edges of joints first by heating and then joined by cooling. Welded connection has 95 – 98% the
strength of the solid member being connected.
Butt weld: they are called single V, double V, single U, double U, single J, single bevel, double
bevel depending on shape of the cut of joining surfaces.
Fillet welds: according to the welding position, fillet welds can be flat, horizontal, vertical or
overhead.
Structural steel members and their inter connections
1. Compression members
2. Beams and girders
1. Compression members
A compression member is a member subjected to compressive stresses in a direction parallel to
principle axis. The compressive stresses have a tendency to buckle the member laterally or
shorten it along the axis. Hence, in the design of compression members its area of cross section
and length should be given due considerations. Columns and stanchions are well known
examples for compression members.
Columns and stanchions
When a pillar is of circular cross section or if it is in the form of cylinder, it is termed as columns.
The column may be hollow or solid in section. Stanchion: compression member cast into
rectilinear form or built up from rolled steel section. Steel stanchions may be of single rolled steel
section or built up section of one or more sections such as angles, channels, plates and I section.
From functional point of view, column or stanchion is one and the same and hence, the term
column is used in general points.
2. Beams and girders
Steel beam consists of single rolled steel sections of uniform thickness throughout or may be of
compound sections.

5.6 | Page CE 204 – Construction Technology

Dept. of Civil Engineering, MEAEC Module V
Plate Girders
These are heavy built up beams and are used for carrying very heavy loads over large span. It is a
built up section consisting of angles and plates. Plate girders are deep beam sections, which
require its stiffness to prevent buckling.
Beams and girders
Steel beams may either consist of a single rolled steel section of uniform thickness throughout or may
be of compound sections.
Single angle or I section can be used for carrying very light loads. For heavier loads, built-up section is
used. Steel beams with additional steel plates riveted at top and bottom flanges are used to increase
area and strength. Built up section consists of two or more I beams connected through bolts. For still
heavier beams, a channel section laced back to back at, a proper spacing is used. For still heavier
loads, plate girders are used. Plate girder consists of built up section made up of angles and plates.
Angles and flange plates are held together by rivets. Angle sections or T sections are riveted between
the flanges of the girder at suitable intervals in order to act as stiffeners for resisting buckling under
heavy load.

R.C.C FRAMED BUILDING


An R.C.C framed structure consists of a series of frames which are formed byinterconnecting columns and
 beams at floor and roofs levels so as form an arid of the beams and girders.
 
 Slabs are built monolithically with beams and columns. Walls are constructed within these frames.

The foundation underneath the columns can be either isolated type combined raft or pile depending
 upon the subsoil condition.

R.C.C frames are invariably of monolithic construction by which full continuity throughout the
columns, beams and slabs could be attained. The main advantage of continuous construction
 is reduced deflection and bending moment of the members resulting in the economical
construction of buildings with adequate safety.

 span, secondary beams spanning across main beams can be introduced for better load
In case of larger
distribution.
Construction procedure
In R.C.C frame the form work of different members to be casted is first installed or erected in
position. The reinforcement is then placed and finally the concrete is poured. After the concrete has
sufficiently set the form work is removed.
Concreting of entire building cannot be practically done in single operation and hence construction
joints are required to be provided at intervals. The joints in slabs and beams should be vertical and at
the centre of the span.
Regarding reinforcement following features should be provided.
  
Reinforcing steel is held in position by wiring the bars together at their intersection.
  
Spacers are used to maintain the reinforced steel in position.

In slabs at the centre reinforcement is
provided at the bottom and at the supports,
reinforcement is provided at the top.

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Module V Dept. of Civil Engineering, MEAEC

  are provided at the bottom of the beam and they are bend up near the
In beams horizontal bars
supporting columns.
  
To counteract the effort of shear stresses vertical stirrups are provided.
  
In footings dowel bars from the footing should extend into the columns.

Dowel bars and reinforcement bars of columns of next storey with proper lap should be provided
before concreting of columns.

The columns are sliced or reduced in section as the loads are lesser in upper storey and hence main
bar bend inwards from the lower part and are again made vertical after emerging out of the floor
level.
Provision should be made for vertical transportation i.e. lift, well, staircase etc.
To have rooms of small sizes within the floor area the partition walls should be made in small
thickness and of lightweight materials.
The coping to the parapet wall should be provided with a slope towards the roof so that it will
not drain over the face of the building but it will drain towards the roof.
Reinforcement in concrete
Reinforcement concrete is a composite material in which concrete’s relative low tensile strength and
ductility are counteracted by the inclusion of reinforcement having higher tensile strength and
ductility. The reinforcement is usually steel reinforcing bars and is usually embedded passively in the
concrete before it sets. There should be a good bond between reinforcement and concrete. The
reinforcement should be of high strength. It should have high tolerance to tensile strain. It should be
thermally compatible and durable in concrete environment.
Concreting of columns
Construction procedure:
1. Fixing of longitudinal bar and lateral ties in position.
2. Erection or installation of appropriate shuttering or formwork.
3. Placing of concrete of desired mix and compacting it by hand or vibrators.
4. Curing it by proper technique and removing the formwork after some period (stripping time).
In the case of columns, concreting is done in stages of lift of not more than 1m in height. It should
also be observed that bottom layer should be sufficiently deep compacted and setted before
planning next layer. The concrete is poured centrally into the column.
Reinforced concrete beam
An RCC beam may be rectangular, square, T shaped or L shaped. Rectangular or square RCC beams
are used when the slab resting over the beam is made up of different material. When the slab is cast
monolithically over the beams and it extents on both sides of the beams, a T beam is used. But, when
the slab extents only on one side of the beam and is monolithic, an L shaped beam is formed.
In the case of simple RCC rectangular beam, concrete on tensile side of the beam does not carry any
stress. Hence, only that much concrete is needed which can keep the steel rods in position. This give
rise to T beam shape as shown in figure.
Beam shapes
Sometimes, the size of the beam is limited to fit in to the space which is for an ordinary rectangular or
T beam. In such cases, smaller rectangular beams with reinforcement on compression side in addition
to tensile reinforcement are provided. It is called doubly reinforced beam.
Beam
In order to counteract the effect of diagonal tension stresses (result of the stress and tensile stress),
additional steel bars in the form of vertical stirrups and bent up bars are provided.

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Dept. of Civil Engineering, MEAEC Module V
To counteract the effect of diagonal stresses (as a result of shear stress and tensile stress) additional
steel bars in the form of vertical stirrups and bent up bars are provided. To counteract the effect of
bond stress the ends of mild steel bars are hooked or deformed bars (tor steel bars) are used instead
of mild steel bars.
The minimum tensile reinforcement in a beam should not be less that 0.3% of gross sectional area of
the beam.

Concreting of RCC slabs

RCC slabs may be considered as wide shallow beams. For small spans of floors up to 4m which do not
carry heavy loads, a simple RCC slab may be used. When the ratio of length of the room to its breadth
is greater than 1.5, slabs are designed as one way slab to span along the shorter width. In this case,
main reinforcement run parallel to shorter wall and distribution bars run parallel to longer wall
(parallel to the length of the room). Although no tensile stress exists at the bottom of the slab at the
supports at least ¼ of the bars should run straight through.
The thickness of the slab depends upon several factors such as concrete mix used, anticipated floor
loads, the span or floor plan, etc. Depending upon the building plan, the slab may be simply
supported on the wall or it may be continuous over intermediate walls.
In the case of simply supported slabs, to allow the slab a freedom of movement, the top of the wall is
covered with a layer of plastic and then with a thin coat of bitumen over it. If the building is of RCC
framed construction, then the slab is cast monolithically with the supporting beams. When the length
to breadth ratio of the room is less than 1:5 (i.e., room is nearly square) the floor slab is designed
spanning in both directions and called two way slab. Main reinforcement run in both directions and
mesh reinforcement is provided at top and bottom.
RCC slab construction
1. A well designed centering false work either of
steel or timber is erected to support its own
weight and super imposed load.
2. After centering, the reinforcement is placed on
the interior surface which has been finished
first with a thin coat of oil and then with a thin
layer (2 – 5 cm) of cement concrete.
3. The cement concrete is then poured around
the reinforcement up to required thickness of
the slab and well consolidated by means of
rammers. Slab is concreted in one operation
for the full depth. The top surface of slab is
kept rough to create proper bond with any
type of floor finish.
4. The concrete is then cured for about a week to
attain its full strength.

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Module V Dept. of Civil Engineering, MEAEC
5. After the concrete has been sufficiently hardened, the form work is removed and the upper
and lower surfaces of the slab are treated as desired.
Monolithic construction of beams and slabs
Usually adopted and involves the following operations:
(i) Fixing of designed reinforcement in position of shuttering.
(ii) Placing and compacting of desired concrete mix.
(iii) Curing.
(iv) Removal of formwork.
Reinforced concrete stairs
Reinforced concrete is the preferred material for stairs in residential as well as in office and other
public buildings. For ornamentation, the concrete structures are sometimes covered with wood,
steel. Staircases are common in factories especially in chemical plants. Dog legged reinforced
concrete stairs are used in most residential buildings
Layout requirements of RC stairs
1. Width of stairs: minimum of 40cm in residence and 1.5 to 2 m in public buildings.
2. Length of flight: number of steps in one flight should not exceed 12 to 16 and not be less than
3.
3. Pitch of stair: depends on the rise and tread adopted. The values of rise and tread usually
adopted are as follows:
a) In residences, we give a tread or going of 250mm (9-10 inches) and a rise of 160 – 175
mm approximately.
b) Public buildings should have longer treads and smaller rise. Treads of 270 mm to 300mm
and rises of 100 – 150 mm are usually given.
4. Headroom: minimum clear height from a tread to overhead construction. Eg: the ceiling of
the next floor. Headroom distance should not be less than 2.1 to 2.3 m, so that a person can
use the stairs with a luggage on his head.
5. Height of handrail: 850 to 900 mm.
6. Staircase room dimension: minimum clear width of staircase room should be 2.1 m. (Clear
width of staircase 90cm + width of balustrade 15cm + well of 15cm).
Construction of simple concrete stair
There are two methods.
1. Inclined slab construction: these types of stairs can be built in two ways. Firstly the inclined
slab and steps can be built together with reinforced concrete. Steps can be built with proper
shuttering. Alternatively, in cheaper construction, only the inclined slab is first built in
concrete and steps are later constructed with brick work. This latter procedure considerably
reduces shuttering costs and is commonly used for residences.
2. Cantilever slab construction: in residences, where the traffic is light the individual steps can
be cantilevered from the surrounding walls of a staircase room. Otherwise for very wide
stairs, the individual steps can be centrally supported and cantilevered from a central cast-in-
situ spine beams specially built as a part of stairs. Latter type is common in office buildings.
When they are cantilevered from walls as in residences, it will be desirable to have a concrete
beam in the wall connecting all the ends of the slabs of the stairs to improve stability with
long term use.
***********************************************************************************
FORM WORK OR SHUTTERING
As fresh concrete is in a plastic state, when it is placed for construction purposes , it becomes
necessary to provide some temporary structure to confine and support the concrete ,till it gains
sufficient strength for self-supporting. This temporary structure is known as form work or shuttering.

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Dept. of Civil Engineering, MEAEC Module V
Requirements of form working
Good form work for concrete structures should satisfy the following requirements:
1. It should be strong enough to resist the pressure or the weight of the fresh concrete and the
superimposed loads due to equipment.
2. It should be rigid enough to retain the shape without undue deformation. Therefore it
should be so designed that deflection does not exceed 1/900th of span in normal cases.
3. It must be made or constructed as tight as possible so that it doesn’t allow the cement paste
to leak through the joints.
4. The space enclosed by the form should be true to the size as designed .The form
should therefore not warp, bulge or sink, to meet this requirement.
5. The inside surface of form work should be smooth so as to give good appearance to
the resulting concrete surface.
6. The entire formwork should be so made that it can be removed easily without causing least
injury to the surface or edges of the concrete
7. As the form work doesn’t contribute anything to the stability of the finished structure ,it
should , therefore, be made economical by reducing the cost through proper design,
construction and use of form work
Economy in form work
The following measures or steps should be taken to reduce the cost of form work.
1. The use of irregular shapes or form should be avoid
2. It should be fabricated into modular sizes in a larger number so has to allow reuses of form,
if possible.
3. The structural component should be so designed as to permit the use of commercially
available forms.
4. The working drawing of a form work should be prepared and checked before fabricating it.
5. The components of forms should be prefabricated on ground using power equipment, in
order to reduce labor cost and delays on the work
6. The removal and reuse of forms should be permitted, if it is safe to do so.
7. The forms should be designed to provide adequate but not excessive strength and rigidity
i.e. forms should have a balanced design
8. Where possible adopt assembly line in fabricating forms to increase the efficiency of the
works
9. If possible use double headed nails to facilitate their removal and to reduce the damage the
timber
10. The forms should be cleaned and oiled after each use
11. The use of a construction joints should be made to reduce the quantity of forms and to
make re-use of forms
12. If mechanical vibrators to be used then bolts must be used in place of wire ties or nails to
ensure safety
Materials and sizes of forms
Materials: - the materials to be used for making formworks are decided either by economy or
requirements of the job or both. The materials most commonly used are timber, plywood, steel
and aluminum. In case of specific structures such as round columns, curved surfaces etc. steel is
preferred.
Formwork are mainly of two types
(a) Steel formwork
(b) Wooden formwork
Steel formwork is made of
 Steel sheets
 Angle Iron

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Module V Dept. of Civil Engineering, MEAEC
 Tee Iron
Wooden formwork consists of
 Props
  Planks battens
 Ledgers
 Sheeting
Timber formwork:
 
 Most common material used for bracing the member, hence called as the traditional formwork.

Can easily be cut to size on site. Joist are replaced with engineered wood 
beams and supports are replaced
with metal props. This makes this method more systematic and reusable.
Various sizes of members of timber
Sheeting for slabs, beam, column side 25 mm to 40mm thick
and beam bottom
Joints, ledges 50 x 70 mm to 50 x 150 mm
Posts 75 x 100mm to 100 x 100 mm

Plywood
 This is by far the most common material used for the facing panel. It is easily cut to shape
 on site, and if handled and stored carefully, it can be used many times.
 A standard plywood thickness on site is 18mm. This is usually sufficient for most pours.
 However, if the formwork is curved, a thinner plywood is used to facilitate bending.

 Thicker plywood may be used when the weight of concrete causes a standard
thickness plywood to bow out, distorting the concrete face.
Steel formwork:
Steel forms are stronger, durable and have longer life than timber formwork and their reuses
 are more in number
  Steel forms can be installed and dismantled with greater ease and speed.
 The quality of exposed concrete surface by using steel forms is good and such surfaces
 need no further treatment.
 Steel formwork does not absorb moisture from concrete.
 Steel formwork does not shrink or warp
Aluminium formwork
 Often used in pre-fabricated formwork, that is put together on site.
 Aluminium is strong and light, and consequently fewer supports and ties are required.

 The lighter sections will deflect more, but this can be avoided by simply following the
manufacturers’ recommendations.
Plastic formwork
 Glass reinforced plastics (GRP) and vacuum formed plastics are used when
 complicated concrete shapes are required (e.g. waffle floors).
 Although vacuum formed plastics will always need support, GRP can be fabricated with
 integral bearers making it self-supporting.
 Like steel, plastic formwork can be re-used many times, as long as care is taken not to
scour the surface whilst vibrating the concrete.
Sizes of forms
Sizes should be based on the following criteria

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Dept. of Civil Engineering, MEAEC Module V
1. If forms are prefabricated into panels or sections it is desirable to fabricate sizes as big as
the concrete member or the methods of handling will permit. This is required to reduce the
time and labour cost in erection and removal of forms
2. If the forms are to be handled manually the weight of single panel should not exceed 35
kg per person.
3. If the forms are to be handled by mechanized methods i.e. by power equipments, the sizes
are limited by length of timber available, the dimensions of concrete structures and the
capacity of the hoisting equipments.

Types of forms work

Steel Forms: These forms are made of steel sheets which are reinforced with angle sections and
joined together by keys, wedge or some other devices.
Moving Forms: These forms are used economically, where long lengths of concrete sections have to
be constructed.
Climbing Forms: These forms are used for tall buildings. Climbing forms consist of narrow band of
form work encircling the structure and as the name implies can be raised to the desired heights as
concreting work progresses.

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Module V Dept. of Civil Engineering, MEAEC
PROCESS OF FORMWORK CONSTRUCTION
Construction of formwork:
This normally involves the following operations:
1. Propping and centering
2. Shuttering
3. Provision of camber
4. Cleaning and surface treatment
Formwork for wall
It consists of
• Timber sheeting
• Vertical posts
• Horizontal members
• Rackers
• Stakes
• Wedges
After completing one side of formwork reinforcement is provided
at the place then the second side formwork is provided
Formwork for column
• It consists of the following
– Side & End Planks
– Yoke
– Nut & Bolts
• Two end & two side planks are joined by the yokes and bolts

Erection sequence for a column

Prior to positioning column formwork check that steel for the column has been inspected and cleared
for casting.
- Position formwork for the column from predetermined grids.
- Plumb formwork both ways and securely support using adjustable steel props.
- The propping angle should be 45° to the floor.
- Ensure the steel props are safely secured to the column formwork and the floor, and that adj
ustment for pushing and pulling is operational.
- Set out the positions of column clamps from a storey rod.
- Transfer the column clamp positions from the storey rod onto column formwork.
- Use nails to support the arms of column clamps while wedging.
- Position and wedge the bottom, middle and top clamps sets.
- Check the formwork at the top for square.
- Position and wedge the remainder of the column clamps.
- Using a plumb bob suspended from a gauge block plumb the column.

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Dept. of Civil Engineering, MEAEC Module V
When all the column formwork is securely propped a final check must be made for plumb and colum
n alignment before and immediately after the concrete has been poured and vibrated.
Formwork for beam
  
Beam soffit must be thickened timber or strengthened plywood.
  
Beam sides 18mm plywood or 25mm boards, with studs (cleats) at 500 to 600mm centres.
  
Deep beams (over 600mm) should have walkers and ties.
  
Use angle fillets in the beam side to soffit joint where possible.
 
Allowance must be made for height adjustment of the props or falsework.

Erection sequence for constructing beam formwork includes

  
Position of sole plates;
  
Marking out and setting heights for falseworks;
  
Assemble and position props, adjustable head jacks, falseworks , bearers and Spreaders;
  
Construct and erect side walls and beam soffit.
 
Position of sole plates

Formwork for staircase

Points to consider when designing stair form work:

Stair formwork must support the weight of concrete. The weight of the throat of the stair and the
 steps will have to be supported.

Because of the slope of the stair, some of 
the force is transmitted sideways. All formwork mu st be well tied
 together to prevent sideways movement.

the finish of the stair treads and type of nosing. Space may have to be left for purpo se made
Consider
nosing.

DESHUTTERING
Deshuttering in simple means, the process of removing the shuttering (Formwork for Concrete).
Order and method of removing formwork:

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Module V Dept. of Civil Engineering, MEAEC

 beams & column sides should be removed first. Shuttering forming
Shuttering forming vertical faces of walls,
 soffit to slab should be removed next.

 
Shuttering forming soffit to beams, girders or other heavily loaded members should be removed in the end.

Factors considered:
• Concreting is done under normal circumstances
• Cement used is Ordinary Portland Cement
• Adequate curing is done
• Ambient temperature is not fall below 15 degree
Order and method of removing formwork
The shuttering forming vertical faces of beams and column sides should be removed first. Shuttering
forming soffits to slabs should be removed next. Shuttering forming soffits to beams, girders or other
heavily loaded members should be removed next.

JOINTS
Expansion and contraction joints
All building materials expand or contract due to change in temperature and variation in moisture content.
The magnitude of such expansion or contraction depends upon the type of material used in construction
and extent of variation of temperature and moisture content. In case components of such a structure are
not allowed for free movements, internal stresses will be set up which may result in the formation of
cracks. This may in turn endanger the viability of the structure. Thus, special provision should be made to
control or isolate thermal and other movements to avoid danger to structure. This is achieved by breaking
the continuity of the structure by introducing joints at regular intervals.
Expansion joints
These joints are provided to accommodate the expansion of adjacent building parts and to relieve
compressive stresses that may otherwise develop. The spacing of expansion joints is 30m c/c. In
addition, expansion joints should be provided where a structure changes its direction for instance for
L section, T section and H and U shape structure.
Materials used for expansion joints
Joint filler
It is a readily compressible material which can accommodate the expansion of adjacent parts and the
joint has ability to regain 75% of its original thickness when pressure is released. Joint filler can be
made out of a variety of materials such as bitumen, cork strips, cellular rubber, etc. Filler should be
compressible, rigid, cellular and resilient.
Sealing component
The function of this in a joint is to seal the joint against passage of moisture and to prevent the dust
particles, grit, etc. Mastic or hot applied bitumen sealing compound are commonly used for this
purpose.
Water bar
The function of water bar is to seal the joint against the passage of coater. The water bar may be of
natural and synthetic rubber, PVC or metal. The width of the metal water bar normally varies from 15
to 20cm and the thickness should not be less than 0.56mm. The metal water bar should have a U or V
fold in the middle, to allow for expansion and contraction at the joint.
Provision of expansion joints
Expansion joints consist of gaps (15 to 40mm wide) depending on the type of structure, expected
temperature movement, etc. provided at various places of the building. Thus in masonry walls in buildings
where cross walls restrict the main walls, the joints need not be closer than 25 to 40 m apart. In long
compound walls exposed to the sun, the joints should be closer. In RCC Construction, IS 456

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Dept. of Civil Engineering, MEAEC Module V
(2000) clause 27 stipulates that expansion joints should be provided in changes of direction.
Structures more than 45m in length are to be designed by providing one or more expansion joints. It
is also customary to provide for expansion of slabs bearing on walls by providing slide able bearing.
The concrete is subjected to volume change due to lmany reasons. So we have to cater for this by
way of joint to relieve the stress. Expansion is a function of length. The building longer than 45m are
generally provided with one or more expansion joint. In india recommended c/c spacing is 30m. The
joints are formed by providing a gap between the building parts.
Contraction joint
When concrete sets and hardens in air, it shrinks in volume. The magnitude of shrinkage or
contraction is almost directly proportional to the quantity of water in the mix. Hence, concrete mix
having more water shrinks more than a concrete mix having low slump. The contraction caused due
to drying shrinkage results in development of tensile stresses in concrete. When such tensile stress
exceed the tensile strength of concrete, it results in formation of crack. Contraction joints are
installed to allow for the shrinkage movement in structure.
This joint may be either a complete contraction joint in which there is complete discontinuity of both
concrete and steel or it may be partial contraction joint in which there is discontinuity of concrete but
the reinforcement continue across the joint. It may be noted that in both the cases, no gap is
provided for the joint, but any complete or partial separation of adjacent section is created.

PREFABRICATED SYSTEM
Prefabrication is the practice of assembling compounds of a structure in a factory or other
manufacturing site, and transporting complete assemblies as sub-assemblies to the construction site,
where the structure is to be located by trucks or some other means and finally placing it in position by
cranes or such other devices.
e.g.: Hollow concrete blocks used for load bearing interior and exterior walls, partition walls, piers,
columns, etc. Fencing posts, pipes, joint beams, girders, columns, etc. are also available as precast
members.
Prefabricated building is the completely assembled and erected building at which the structural walls
consist of prefabricated individual units or assemblies using ordinary or controlled materials.
Advantages

 Prefabrication is used to affect economy in cost. These results in
improvement in quality because
components can be manufactured under controlled conditions.
  
The speed of construction is increased since no curing period is necessary.
  
Prefabrication helps to use locally available materials.

 materials i.e., light weight; easy workability, thermal insulation etc. effect
The properties of prefabrication
economy and improve quality.
  
Concrete of superior quality can be produced.
  
Smoother exposed surface.
  
Strong and transportation costs of building materials and equipments are reduced.
  
Prefabricated members can be casted under all weather conditions.
 
Desired shapes with greater accuracy.

Disadvantages:
1. Handling, transportation, lifting and placing requires special equipments.
2. High cost of construction (skilled labour required).
3. Chance of damage during transportation.
4. Difficulty in assembling.
5. Leaks can form at joints in prefabricated components.
The following factors are to be considered while selecting materials for prefabrication.
 Easy availability

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Module V Dept. of Civil Engineering, MEAEC
 Light weight
 Thermal insulation
 Easy workability
  Durability in all weather conditions
 Economy in cost
 Sound insulation
Components of prefabricated construction
The system of prefabrication construction depends on the extent by which the prefabricated
components, their materials and techniques are adopted in the building construction.
(1) Flooring and roofing system
For this purpose precast slabs or other precast structural units are used.
(2) Open prefabricated system
This system is based on the use of structural elements to form whole or part of the building. The
structural prefabricated components used are:
(i) Reinforced concrete channel
(ii) Hollow brick
(iii) Pre-stressed/Reinforced concrete beams
(iv) Precast lintels and sunshades
There are two categories of open prefabrication system
1. Partial open prefabrication system
Under this system, precast roofing and flooring components and other minor elements like
lintels, sunshade, kitchen sills, shelves, etc. are used. These can be done on the site / off the site.
2. Fully prefabricated system
Large paneled prefabricated system:
The components used are precast concrete large panels for walls, floors, roofs, balconies,
staircases, etc. The casting of components can be on the site or off the site.
Structural scheme with precast large paneled wall, can be classified as cross wall system and
longitudinal wall system.
Cross wall system: In this system, the cross walls are load bearing walls and longitudinal walls are
non-load bearing walls. This system is suitable for high rise buildings.
Longitudinal wall system: In this system, the longitudinal walls are load bearing and cross walls
are non-load bearing walls. This system is suitable for low rise buildings.

SLIP FORM CONSTRUCTION

Slip form construction is a continuous construction technique in which concrete is poured into a
continuously moving form. Slip form is used for tall structures (e.g.: bridges, towers, buildings, lift
shafts and dams) as well as horizontal structures such as roadways. Slip forming enables continuous,
non-interrupted cast-in-place flawless concrete structures which have superior performance
characteristics. It also results in saving of time. Slip forming relies on the quick setting properties of
concrete and requires a balance between quick setting capacity and workability. Concrete needs to
be workable enough to be placed into the form and consolidated, yet quick setting enough to emerge
from the form with strength. The height of the formwork is designed in such a way that while the top
of the formwork is being filled by concrete the lowest layer of concrete poured earlier has already
gained an initial set. When the formwork is moved upwards the concrete that is then exposed
remains firm.
In vertical slip forming, concrete form may be surrounded by a platform on which workers stand,
placing steel reinforcing rods into concrete ensuring a smooth pour concrete form and platforms are

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Dept. of Civil Engineering, MEAEC Module V
raised by means of hydraulic jacks. Slip form raise at a rate which permits the concrete to harden by
the time it emerges from the bottom of the form.
In horizontal slip forming for pavements and traffic separation walls, concrete is laid down, vibrated,
worked and setted in place while the form itself slowly moves ahead at a rate of about 300mm/h.
This method can be used to form any regular shape or core. It supports itself on core and does not
rely on support from other parts of the building or permanent works.
Slip form methods of construction can also be adapted to horizontal structures and are used for
paving, canals, and tunneling.
The technique is more in use for structures that have continuous walls like silos, chimneys, and piers
for very tall bridges.
It has also been successfully used for construction of buildings, although this requires the manner of
leaving inserts for openings like doors and windows to be decided well in advance, as well as also any
necessary inserts to support floor slabs after the walls are constructed.
Procedure

Commonly the formwork has 3 platforms.

1. The upper platform act as a storage and distribution area.
2. Middle platform, which is the main working platform, is at the top of the poured concrete level.
3. The lower platform provides areas for concrete finishing.

  
Assembly can only start once the foundations are in place and the wall starter is in correct alignment.
  
Slip form shuttering is aligned with the help of yokes.
  
Horizontal crossbeams connect these yokes.
  
Hydraulic jacks are attached to these crossbeams for simultaneous upward movement.
  
Height of the slip form ranges from 1.1 to 1.5 meters.
  
Yokes and crossbeams also used to support the working platform.
  
Structure should be rigid and shape maintained at all times.
  
Make sure there is no lag or else it prevents the structure from free upward movement
 
It is also possible to reduce wall thicknesses

CE 204 – Construction Technology 5.19 | Page

Module V Dept. of Civil Engineering, MEAEC


as the construction gains height and arrangements have to be made in the slip form structure that will
enable such reduction at regular intervals
Structural Concerns

It is necessary to use a low slump concrete in slip forming processes where the formwork is
moved horizontallyin order for the slab or pavement to retain its shape as the paving
 machine advances.

Presently, slip form pavements use "high early strength" concrete, which achieves the
 approximately 12 hours, as compared to conventional concrete which
required strength in
requires 5-14 days.

The water content of this type of concrete is lower than it is for standard material, resulting
in improved strength as well as improved resistance to the permeation of  salt, thereby
increasing the finished concrete's resistance to deterioration from chloride ions.
Benefits
1. Careful planning of construction process can achieve high production rates.
2. It does not require the crane to move upwards, minimizing crane use.
3. The formwork operates independently; formation of the core in advance of the rest of the
structure takes it off the critical path enhancing main structure stability.
4. Availability of the different working platform in the formwork construction allows the
exposed concrete at the bottom of the rising formwork to be finished, making it an
integral part of the construction process.
5. Certain formwork construction permits construction of tapered cores and towers.
6. Slip form construction requires a small but highly skilled labour force on site.
7. A major cost of concrete structure construction is the required formwork to retain the
concrete till it can be safely de-shuttered and be able to support itself and other imposed
loads. The formwork needs to be continually removed to newer locations and then re-
erected. Continuous use of manpower and lifting equipment like cranes. In the case of slip
form building, the formwork is erected only once and remains intact until the entire structure
is completed.
8. Great reduction in the cost of formwork as well as time saving for re-erection.
9. Cost effective
10. The reduction in the movement of formwork and workers also leads to far more safe
working conditions that also make it a major advantage
Other consideration
1. This formwork is more economical for building more than 7 storey high.
2. Little flexibility for change once continuous concreting has begun. Therefore, extensive
planning and special detailing are needed. Setting rate of the concrete had to be constantly
monitored to ensure that it is matched with speed at which the forms are raised.
Precautions
  Concrete is continuously protected against loss of moisture and rapid temperature changes for 7 days


  
Unhardened concrete is protected from rain and flowing water
  
Prevent plastic shrinkage
 
Plastic cracks are filled by injection of epoxy resin.

*******************************
Prepared By
NAJEEB. M
Assistant Professor
Dept. of Civil Engineering
MEA Engineering College

5.20 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module V

Building Planning for Staircases

Symbolic Meaning of Staircase

 A stair is a series of steps arranged in such a manner to

connect different floors of a building
 Stairs are designed to provide an easy and quick access to
the different floors

 A staircase is an enclosure which contains the complete
stairway

Angkor Wat Steps, Cambodia

Reflecting Architectural Movement Staircase as a Lifestyle

Paris Opera House by Charles Garnier, Beaux Arts Architecture Movement

Glass Spiral Staircase at Apple Store , Boston

CE 204 – Construction Technology 5.21 | Page

Module V Dept. of Civil Engineering, MEAEC

Staircase Terminology

Nosing

Riser
STAIRCASE TERMINOLOGY

Tread

Staircase Terminology Staircase Terminology

Handrail

Landing
Min Headroom
Balustrade

Total rise
Landing Pitch line
Pitch

Total going

Baluster : vertical member supporting the  Riser: vertical member b/w two threads

handrail  Rise: vertical distance b/w the upper faces of

 Balustrade: combined framework of hand rail any two consecutive steps

and baluster  Landing : platform provided b/w two flights


Flight : series of steps without any platform  Nosing : outer projecting edge of a thread

or landing  Going : width of the tread b/w two successive risers

Tread : upper horizontal part of a step 

Step : portion of stair comprised of the  Handrail : protective bar placed at a convenient

thread and riser distance above the stairs

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 Dept. of Civil Engineering, MEAEC Module V

Straight stairs
Quarter turn stairs
Half turn stairs
Three quarter turn stairs

TYPES OF STAIRCASES Circular stairs

Spiral stairs

Curved stairs
Geometrical stairs

Bifurcated stairs

 There is no change in direction on any flight b/w two

successive floors

 Straight stairs can be:

 Straight run with a single flight

 Straight run with a series of flights b/w floors 

 Parallel stairs

 Angle stairs
Straight Flight Staircase

Straight two‐flight stair

with half‐landing

CE 204 – Construction Technology 5.23 | Page

Module V Dept. of Civil Engineering, MEAEC

 Provided when the direction of the flight is to be changed by

90⁰
 The change in direction can be effected by either introducing a

quarter space landing or by providing winders at the junctions

Quarter‐turn stair with landing

Quarter‐turn stair
with winders

 These stairs change their direction through 180⁰


 It can be either dog-legged or open newel type

 In case of dog-legged stairs the flights are in opposite
directions and no space is provided b/w the flights in plan

 In open newel stairs, there is a well or opening b/w the flights

Dogleg stair with half‐landing

5.24 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module V

These type of stairs change their directions through 270⁰

 In other words direction is changed three times with its
upper flight crossing the bottom one

 These stairs , when viewed from above, appear to follow a

circle with a single centre of curvature and large radius
 Generally provided at the rear of a building to give access
for servicing at various floors

 Similar to circular stairs except that the radius of curvature is

small
Stairs may be supported by a centre

postOverall dia 1 t0 2.5 m

Circular stair with central well

CE 204 – Construction Technology 5.25 | Page

Module V Dept. of Civil Engineering, MEAEC

 If a quarter turn stair is branched into two flights at a

landing is known as a Bifurcated stair.

 Commonly used in the public buildings near the entrance hall

 The stair has a wider flight at bottom which bifurcates into

two narrower flights at the landing.


 One turn into left and the other to the right.

 This staircase has either equal or unequal flights.
Spiral stair with central column

 Timber or Wooden Stairs


 Stone Stairs

 Brick Stairs

 Steel Stairs

 Concrete Stairs

5.26 | Page CE 204 – Construction Technology

Dept. of Civil Engineering, MEAEC Module V

Projection

2.0 m headroom

Landing

Building Code on Staircase Handrail

Pitch line

Landing

No projection, other than handrails, is allowed in a staircase

within a height of 2.15 m from the landing or pitch line.

CE 204 – Construction Technology 5.27 | Page

Module V Dept. of Civil Engineering, MEAEC

Pitching Width of Staircase

900mm

Landing 900mm

Handrail

Pitch line

Landing
900mm
The width of every staircase shall not be
less than 900 mm
The minimum and maximum pitch should be 25⁰ and 40⁰. The width is measured from the inner side
of the wall till balustrade or handrail.

Risers Treads

Riser
175 to 185mm

Tread
250 to 325mm

The most comfortable height of a riser is 175mm to The width of a tread shall not be less than 250 mm
185mm The risers and treads within each flight of stairs shall
be of uniform height and size.

Landings of Staircase
Risers & Treads

Generally the following formulae shall

min 900mm
be used
1. Product of riser and tread must be between 400 The number of steps in a flight should
generally be restricted to a maximum
to 410 of 12 and minimum of 2.
2. Riser plus tread must equal 42.5 to 43.5cm
A landing shall be provided at every
3. Sum of tread and twice the riser must lie floor level and door opening.
between 60 cm and 64cm
An intermediate landing shall be
provided in between floor levels at
intervals of not more than 12 risers.
min 900mm
The length of any intermediate
landing, measured in the direction
of travel, shall not be less than 900
mm.

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 Dept. of Civil Engineering, MEAEC Module V

Headroom Handrail

A handrail shall be provided on at least

one side of the flight of
staircase.
2.0 m headroom
The height of the handrail shall be
Landing between 750 mm and 900 mm above
the pitch line.
Handrail
Handrail A handrail need not be provided for a
flight of not more than 5 steps.

Pitch line A handrail may terminate at the

Between landing and the ends of the handrail
750mm – should be properly formed or rounded
Landing 900mm off so that they do not pose a danger to
Pitch line the user.

The headroom of any staircase shall not be less than 2.0 m.

Width of Staircase & Landings Handrail

Width min 900mm

landing min 900mm

The width of stairs is to be of minimum width of 900 mm and should be

adjusted according to the expected flow of traffic. Handrails should be provided on both sides (at least one side) of the
stairs and continuous throughout the entire length.
Floor landings shall have a level platform of the same width as that of the stairs.

Handrail

800 ‐ 900mm

>300mm

After a maximum of 12 risers an intermediate landing should be provided.

Handrails shall extend at least 1 tread depth or 300 mm beyond the top and
bottom step. Staircases of widths wider than 2300 mm should be separated by a handrail
into segments between 1100 mm and 1800 mm.
The height of the handrails is to be between 800 mm and 900 mm

CE 204 – Construction Technology 5.29 | Page

Module V Dept. of Civil Engineering, MEAEC

LIFTS

1 4

Elevator or lift Types of elevators

• Passenger Elevator
• The elevator (or lift ) is a type of vertical transport equipment
• A lift designed for the transport of passengers.
that efficiently moves people or goods between floors
• All types of passenger lifts have different capacity and speed.
(levels, decks) of a building, vessel or other structure.
• Latest passenger lift
• Elevators are generally powered by electric motors that • s comprises of VVVF (Variable Voltage Variable Frequency) Close
either drive traction cables or counterweight systems like a loop microprocessor Controller with sophisticated steel cage &
hoist, or pump hydraulic fluid to raise a cylindrical piston like latest electronic components for minimum and easy maintenance

a jack as well as low power consumption as per today's need.

2 5

Types of elevators
• Goods Elevators
• A lift designed primarily for the transport of goods but which may
carry a lift attendant or other person necessary for the unloading
and loading of goods.
• Goods Elevators are used in different industries for lifting heavy
goods and items.
• These goods elevators are precision designed to have excellent
lifting capacity & maintenance less working mechanism.

3 6

5.30 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module V

Types of elevators Types of Lifts

• Service Lift (Dumb‐Waiter) :
• Drive system
• A lift with a car which moves in guides in a vertical direction; has • Hydraulic
net floor area of 1 m², total inside height of 1.25 m; and capacity • Traction (Machine lift)

not exceeding 250 kg; and is exclusively used for carrying

materials and shall not carry any person.

7 10

Basic Requirements Advantages – Hydraulic lift

• Electrical panels and power outlets. • Lower cost of equipment & its maintenance
• Ventilation fan and lighting in engine room. • More efficient building space utilization
• Power sockets in the lift pit. • Overhead machine room isn’t required.
• Maintenance works. • Most effective for high load capacity requirements

• It imposes no vertical loads on the building structure, column

sizes can be reduced significantly in the hoist way area.

8 11

Physical Requirements Disadvantages– Hydraulic lift

• Size of lift shaft – depends on lift cargo capacity • Performance of hydraulic elevator becomes erratic as the oil

• Depth of lift shaft – depends on the speed of elevator in the system varies in temperature.

• Area of space in lift – depends on speed of elevators. • It has no safety device to prevent its falling it depends wholly
on the pressure .
• Mechanical room size – depends on type and size of the lift
• Inherently high heat producing device.
equipment.

9 12

CE 204 – Construction Technology 5.31 | Page

Module V Dept. of Civil Engineering, MEAEC

Traction (Machine) Hydraulic

Traction Lifts (Machine lifts)
• The ropes are attached to the elevator car, Lifted by ropes, which pass over a Supported by a piston at the bottom of
wheel attached to an electric motor the elevator that pushes the elevator
looped around a sheave & connected to an above the elevator shaft. up as an electric motor forces oil or
electric motor. another hydraulic fluid into the piston.
• When the motor turns one way, the sheave
raises the elevator; when the motor turns the Used for mid and high‐rise applications. Used for low‐rise applications of 2‐8
other way, the sheave lowers the elevator. stories.

Principle : see ‐ saw Principle : Pascal’s pressure principle

• Typically, the sheave, the motor and the
Components : control system, sheave, Components : tank, motor, valve,
control system are all housed in a machine
motor, counterweight, guiding rail. actuator.
room above the elevator shaft.
• The ropes that lift the car are also connected The machine room is located at the The machine room is located at the
to a counterweight, which hangs on the other upper most level, i.e., on the terrace lowest level adjacent to the elevator
shaft.
side of the sheave.
13 16

Requirements for machine room

• The entrance door shall have sufficient opening
to allow for in & out of machines.
• Shall not be any common wall/slab between
machine room and water tank.
• Shall not be used as a store room or for any
purpose other than housing the machinery
connected with the lift installation.
• Shall not act as a passage to any other room or
utility.

14

Requirements for machine room

• Adequately ventilated.
• The equipment are protected as far as possible from dust
and humidity.
• Temperature 5° C – 40° C
• Walls, ceiling, floor should be finished in tiles or painted as a
min to stop dust

15

5.32 | Page CE 204 – Construction Technology

Module V Dept. of Civil Engineering, MEAEC

Design and layout consideration

Escalators • Escalators, like moving walkways, are often powered by

constant‐speed alternating current motors and move at

Escalator = Elevator + Scala (Steps)
approximately 1–2 feet (0.3–0.6 m) per second.

• The typical angle of inclination of an escalator to the

horizontal floor level is 30 degrees with a standard rise up to

about 60 feet (18 m).

1 4

• Modern escalators have single‐piece aluminum or stainless

• An escalator is a moving staircase – a conveyor transport device
steel steps that move on a system of tracks in a continuous
for carrying people between floors of a building.
loop.
• The device consists of a motor‐driven chain of individual, linked • A number of factors affect escalator design, including physical
steps that move up or down on tracks, allowing the step treads requirements, location, traffic patterns, safety considerations,
to remain horizontal and aesthetic preferences.

• Foremost, physical factors like the vertical and horizontal

distance to be spanned must be considered.

2 5

• Escalators are used around the world to move pedestrian traffic

in places where elevators would be impractical.

• Principal areas of usage include department stores, shopping

malls, airports, transit systems, convention centers, hotels,

arenas, stadiums and public buildings.

3 6

CE 204 – Construction Technology 5.33 | Page

Module V Dept. of Civil Engineering, MEAEC

Components of escalators Components of escalators

• Landing platform: • Steps:
• The steps themselves are solid, one piece, die‐cast aluminum
• These two platforms house the curved sections of the
or steel.
tracks, as well as the gears and motors that drive the
• The steps are linked by a continuous metal chain that forms
stairs. a closed loop.
• The top platform contains the motor assembly and the • The front and back edges of the steps are each connected to
main drive gear, while the bottom holds the step return two wheels.
• These are basically moving platform on which escalator
idler sprockets.
passengers ride.

7 10

Components of escalators Components of escalators

• Floor plate: • Handrail:
• It provides a place for the passengers to stand before • The handrail provides a convenient handhold for
they step onto the moving stairs. passengers while they are riding the escalator.
• This plate is flush with the finished floor and is either • In an escalator, the handrail is pulled along its track by a
hinged or removable to allow easy access to the chain that is connected to the main drive gear by a series
machinery below. of pulleys.

8 11

Components of escalators Components of escalators

• Truss: • Deck board:
• The truss is a hollow metal structure that bridges the • These are used for preventing clothing from getting
caught and other such problems.
lower and upper landings.
• Balustrade:
• It is composed of two side sections joined together with • The side of an escalator extending above the Steps,
cross braces across the bottom and just below the top. which includes Skirt Guard, Interior Panel, Deck Board
and Moving Handrails
• The ends of the truss are attached to the top and bottom
landing platforms via steel or concrete supports.
• The truss carries all the straight track

9 12

5.34 | Page CE 204 – Construction Technology

Module V Dept. of Civil Engineering, MEAEC

Types of escalators Advantages of Escalators

• Parallel: These type of escalator go • It helps a large no. of people in moving from one place to another at
up and down simultaneously. the same time and they reduce the need of elevator because people
would not have to wait for elevator and escalator can carry a large
• Speed: 0.5m/s no. of people at the same time.
• Inclination: 30°, 35° • It is helpful for the people that have pain in their legs and joints i.e. it
• Step width: 800 / 1000 provide comfort to the people
• Power: 50 Hz / 3p • Escalators are effective when used as a mean of guidance and
circulation.
• Handrails: Rubber /Stainless steel
• Their speed can be adjusted which is helpful in managing the crowd.
• Step: stainless steel • When turned off they can be used a staircase.
• Landing plate: anti skid
stainless steel.
13 16

Types of escalators
Disadvantages of Escalators

• Multi parallel: • Waste of energy when not in use.

• Speed: 0.5m/s
• Inclinations: 30°, 35° • Possible injuries when stopped suddenly
• Step widths: 800 / 1000
• Power: 50 Hz / 3p
• Handrails: Rubber /Stainless
steel
• Step: stainless steel
• Landing plate: anti
skid stainless steel

14 17

Types of escalators Lifts (Elevators) Escalators

Closed cabins inside vertical shafts that Moving stairways that allow people to
• Spiral type escalators: are used to transport people between move between floors in busy places
different floors in high rise buildings such as shopping malls, airports, and
• These are used to enhance the railway stations.
architectural beauty and to save
the space. Lifts are fast and can move up or down These are slow moving ‐ horizontal &
at great speeds ‐ vertical movement. incline movement.
• Inclined Angle : 30°
Move up or down using counterweights The steps of are fixed and linked
• Rated Speed [m/sec] : 25 or traction cables together and move up but come down
• Number of Persons : 6300 per from behind on a conveyor belt that is
hour driven by a motor.
• Rated Speed (m / sec.) :25 m/ Less space is used for its construction Space used is same as the staircases &
min. as the elevator is limited to the shaft & connects 2 floors .
• Vertical Rise ( m ) : 3500 ~ 6600 machine room, which connects all the
floors.

15 18

CE 204 – Construction Technology 5.35 | Page

Module V Dept. of Civil Engineering, MEAEC

Ramps
• Ramp is a sloping surface connecting the floors at
different levels
• It is provided to facilitate physically challenged people or
patients to move from one floor to other.
• Provided in places like railway stations, hospitals where
large number of people move from floor to floor
• Required in multi‐storey parking facilities also
• The slope of ramp should not be more than 1 in 15
• A ramp may be straight, dog legged, zig‐zag or curved
• Hand rails are to be provided on both sides of ramps
• The surface of ramp should be non ‐ slippery
19

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MODULE 6
Module VI Dept. of Civil Engineering, MEAEC

RETROFITTING
Why retrofitting is required ?
Problem faced in concrete structure
 Damage to structural members.
 Excessive loading.
 Errors in design or construction.
 Modification of structural system.
  Seismic damage.
 Structural cracks.
 Corrosion due to penetration- honey combs.
What is a retrofitting?
 Retrofitting is the seismic strengthening of existing damaged or undamaged structures.

 It is an improvement over the original strength when the evaluation of the building indicates
that the strength available before the damage walls insufficient and restoration alone will not
be adequate in future quakes.
Objectives of retrofitting
 Increasing the lateral strength in one or both directions, by reinforcement or by increasing
wall areas or the number of walls and columns.

 Giving unity to the structure by providing a proper connection between its resisting elements.
To retrofit or not?

Seismic load capacity versus risk of building collapse

6.31 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module VI
RETROFITTING TECHNIQUES

1. Adding shear wall

 Used for non-ductile reinforced concrete frame
 buildings.
 A new shear wall can be cast in-situ or precast
 concrete elements.
 It can be placed at the exterior wall of building,
 however it may cause in the appearance.
 Increase the lateral strength, ductility and stiffness
of the building substantially.


2. Adding infill wall

  This is the brick masonry infill wall.

 Installed tight to surrounding concrete
 elements.
 The lateral stiffness of a storey increases
 with infill wall.
 Due to ‘strut action’ of the infill walls, the
flexural and shear forces and ductility
demand on the ground storey columns
 are substantially reduced.
 Do not increase the ductility of structure.

Brick masonry infill wall retrofitting

CE 204 – Construction Technology 6.32 | Page

Module VI Dept. of Civil Engineering, MEAEC
3. Adding steel bracing
 An effective solution when large openings are required.
 Increase in strength, ductility and stiffness.
  Opening for natural light.
 Adds much less weight to the existing structure.

4. Wall thickening techniques

 Increase the thickness by adding bricks, concrete and steel reinforcement.
 It can bear more vertical and horizontal loads.
 Does not cause sudden failure of the wall.

Wall thickening by reinforce Concrete

5. Adding wing wall or buttress
 To increase lateral strength, ductility and stiffness of structure.
 The wing wall are placed on the exterior side of an existing frame.

Quadra elementary school, Canada

6.33 | Page CE 204 – Construction Technology

 Dept. of Civil Engineering, MEAEC Module VI
6. Mass reduction
 In this process removing one or more storey of building as shown in figure.
 Decrease the load at foundation.
 Increase the life and strength.

Mass reduction by removing one story

7. Base isolation
 Isolation of superstructure from the foundation is known as base isolation.
  It is the most powerful tool for passive structural vibration control techniques.
 Isolates building from ground motion lesser seismic loads, hence lesser damage to the
 structure, minimal repair of superstructure.
 Building can remain serviceable throughout construction.
 Does not involve major intrusion upon existing superstructure.

Base isolation of building

8. Jacketing of structural elements
 This is the most popular method for strengthening of concrete building elements like as

1. Beams
2. Columns
3. Beam column Junctions
 Due to jacketing, enhancing the shear strength, concrete confinement, flexural strength

 Materials to be used

 Steel plates
 Fiber reinforce polymer (FRP wrap)

CE 204 – Construction Technology 6.34 | Page

Module VI Dept. of Civil Engineering, MEAEC
(i). Carbon fiber reinforce polymer (CFRP)
Use of CFRP in structural strengthening
a) CFRP STRIPS
 Performance of CRPF strips depend on the strength of adhesive used to bond the
 strips to the concrete surface.
 Strong, ductile and durable structural system can be achieved.
 These are four times stronger than structural steel.

b) CFRP WRAPS
 Mainly used for corrosion control and retrofitting of rcc members.
 resistance to collapse under earthquake loading
  In a circular column an increase in axial capacity is also achieved by wrapping.
 the confinement of the CFRP wrap enhances the compressive strength of the concrete
 and increase in load bearing strength.
 Immediate strength gain and open to traffic.
(ii). Glass fiber reinforce polymer (GFRP)

 Steel reinforced
concrete Advantages
  
Enhanced strength.
  
Increased shear capacity of columns.
 
Technique is easy and it does not need special design criteria.

Disadvantages
  
Increase in member cross section- less floor area.
  
Increase dead weight due to extra steel and concrete.
  
Prone to high level of corrosion.
  
Requires more construction time as it involves curing.
  
Production of dust and debris causes pollution and health hazards.
 
Needs shuttering, formworks, reinforced steel, concrete, concrete pumps, vibrators, etc..,

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 Dept. of Civil Engineering, MEAEC Module VI

Retrofitting at junction by steel plate Retrofitting of column by CFRP wrap

Retrofitting by steel reinforce concrete

9. External plate bonding
 Steel plates are attached to the surface of damaged members forming a three phase steel
 composite system
 Acts as supplement to existing reinforcement.
 Attachment of steel to concrete
 Adhesive connecting mechanism (glue).
 Bolting connecting mechanism.
  Advantages
 Stress reduction due to the external steel
 plate.
  Enhances load bearing capacity.
 decreases chances of cracks and
 deflection.
 Disadvantages
 Increase in dead load.
  High installation cost due to heavy weight of steel plate.
 If there is any indications of corrosion in the reinforcement this technique cannot be
 used.
 Susceptible to high level of premature de-bonding.
 Chances of corrosion is high.
 Bonding between concrete and steel plate.
 Reaction between epoxy adhesive and concrete.

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Module VI Dept. of Civil Engineering,
10. External post tensioning
 High strength steel strands or pre-stressing tendons are used.
 Tendons are pulled and connected to anchor points on member.
  Very much suitable for retrofitting of bridges.
 Advantages
o Ability to restress, destress and exchange any external pre-stressing cable.
o Crack free members.
o Reduce deflection.
o High fatigue and impact resistance.
o Immediate enhancing of load bearing capacity.
 Disadvantages
o Usually requires a greater section depth.
o Exposed to environmental influences.
o Handling of the tensioning devices may be more difficult.
o High cost.
o Prone to corrosion.
o Skilled person is needed for post tensioning

11. Ferro cement covering

 Composite material reinforced with wire mesh and cement mortar modified with chemicals
 or polymers with closely spaced layer.
 Process involves surface preparation, orientation of wire mesh and Ferro concrete finishing.
 Advantages
 Enhanced resistance to cracking
 Capacity to carry heavy loads.
  High flexural stiffness compared to ordinary cement.
 Resistance to penetration of water.
 Provide resistance to fire, corrosion and earthquake.
 Disadvantages
  Number of labor will be higher.
 Rust can be developed on reinforcement if not covered properly by mortar.
 It is hard to do welding, screw, nut etc.., properly.
 Binding rod and mesh along can be time consuming.
 Proper curing is required.
 Increases dead weight.

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 Dept. of Civil Engineering, Module VI

12. Retrofit by grouting

 Easiest process which involves placing of cementitious material in to the cracks created from
 excessive loading in concrete member.
 Pressure grouting is generally used.
 It is commonly used when honey combs are observed.
 Prevents reinforcement from corroding.
  Very low or no strength gained.
 After grouting proper curing has to be done but often it is neglected.
 Not effective as other techniques.

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Prepared By
NAJEEB. M
Assistant Professor
Dept. of Civil Engineering
MEA Engineering College

CE 204 – Construction Technology 6.38 | Page