Properties of building materials 2 Density: It is defined as the mass of a material per

unit of its volume.

The properties of various building Materials(have to be
ascertained for purposes of specifying them for particular 3 Bulk density or unit weight: The mass per unit vol-
use, classifying them and testing them for acceptance) ume of a material in its natural state.
may be classified into following categories:
4 Porosity: The degree by which the volume of a mate-
1 Mechanical properties, (e.g. elasticity, plasticity, hard- rial is occupied by pores is indicated by the term po-
ness, strength, etc.) rosity. The strength, bulk density, durability, thermal
conductivity, etc. of a material depend on its porosity.
2 Chemical properties, (e.g. chemical composition, acid-
ity, alkalinity, corrosion, etc.) 5 Water absorption: The water absorption of a mate-
rial is its ability to absorb and retain water. This prop-
3 Electrical properties, (e.g. resistivity, conductivity, di-
erty is important in the case of stones, bricks, etc.
electric strength, etc.)
6 Hygroscopicity: It is the property of a material to ab-
4 Optical properties, (e.g. light transmission, colour,
sorb water vapour from air, as in the case of salt, sugar,
reflectivity, refractive index, etc.)
etc., timber, is a hygroscopicity material.
5 Thermal properties, (e.g. specific heat, thermal con-
7 Permeability: It is the capacity of a material to per-
ductivity, thermal expansion, etc)
mit water to pass through it under pressure. It is im-
Physical properties portant in the case of soils.
Depending on the type of materials, these include a num- 8 Fire resistance: It is the ability of a material to resist
ber of properties like; the action of high temperature without losing its load-
1 Specific gravity: It is the ratio of the weight of mate- bearing capacity.
rial per unit volume (not including air holes and pores) 9 Durability: Durability is the resistance of a material
to the weight of an equal volume of water under its to destruction by natural agencies.
standard conditions. It is used to calculate the den-
sity and porosity of materials.

Building stones
Objectives: At the end of this lesson you shall be able to
• define rock and building stone
• explain the characteristics of good building stones
• classify the rocks
• identify type of stones available in India
• explain testing of stone.

Introduction Fineness of grain: Fine grained stone are suitable for

molding works.
Stones are obtained from rocks, which may be classified
according to geological, physical, chemical and practical Compactness: Compact stone can with stand the effects
classifications. A particular building stone may be selected of external agencies effectively.Durability of stone is
depending on the requirements of the structure to be built. decided by their compactness or density of composition.
Definition: Resistance to fire: Should have homogeneous
composition and be free from calcium carbonate or oxide
The soldified definite portion of earth's surface has not of iron.
definite chemical composition and shape is called rock.
Electrical resistance: The stone must be non-absorbent
The quarried pieces of rock which is using for engineering like slate.
purpose are called stone.
Hardness and toughness: To resist wear and tear, the
Characteristics of a good stone
stone must be adequately hard and tough. Hardness may
To find the suitability of stones under different conditions, be tested by scratching with a pen knife and toughness
the following characteristics should be considered. tested by hammer.
Appearance and colour: Have the ability to receive good Strength: The crushing strength of stone should be greater
polish, a pleasing colour and be free from cracks and them 100N/mm2. All igneous rocks have around 100N/
spots. mm2and same of the metamorphic rocks also satisfy this
requirement. Sedimentary rock has a low strength.
WEIGHT: A heavy stone possesses more compactness
and less porosity. Specific gravity: For docks, harbors, gravity dams etc
stones should have a high specify gravity, not less 2.6.The
Porosity and absorption: If it present in greater extent
more specify gravity; more will be the weight of the stone
it makes the unsuitable for building construction.
for a given volume.

84 Construction - D’man Civil - R.Theory For Exercise 1.2.17

Durability: A stone is more durable, if it is compact, Cost: An important consideration in the selection of
homogeneous and free from any Materials affected, also building stone.
have negligible water absorption.
Seasoning: Stone must be free from quarry sap, after
Dressing: Stone should possess uniform texture and quarrying and dressing, stone should be left for a period
softness if it is to hard, finish will be poor and dressing of 6-12 months for proper seasoning.
uneconomical
Classification of rocks

ROCKS

GEOLOGICAL PHYSICAL CHEMICAL PRACTICAL

Depending upon how the Depending upon what Depending upon its Based on uses
rocks was originally its structure chemical composition
formed

Igneous-Primary eruptive or Stratified-These rocks Silicious- Silicon is Granite,

un-stratified rocks, etc. e.g. have many strata or layer. more Basalt,
Trap or Basalt, Granite, etc. e. g. limestone, Slate and e.g. Sandstone, Granite. Laterite,
Sedimentary-Stratified or Sandstone. Calcareous- Lime is Limestone,
aqueous rocks, e. g. Lime Un-Stratified-These rocks more e.g.Limestone, Sandstone,
stone, Sand stone, etc. do not have strata and have Marble, etc. Slate etc
Metamorphic- e. g. Lime granular structure. E.g. Argillacious- Clay is
stone changes to Marble, Granite, Trap, Marble etc. more, e.g. Slate, Schist.
Slate Foliated-These can be split
along definite planes. E.g.
Gneiss.

Types of Rocks get consolidated under pressure and by heat. Chemical

agents also contribute to the cementing of the deposits.
Rocks may be classifed in the following three ways: The rocks thus formed are more uniform, fine grained and
1.Geological 2.Physical 3.Chemical compact in their nature.
GEOLOGICAL CLASSIFICATION They represent a bedded or startified structure in general.
Sand stones, lime stones, mud stones etc. belongs to
Based on their origin of formation stones are classifed this class of rock.
into three main groups- igneous, sedimentary and
metamorphoric rocks. Metamorphic rocks: previously formed igneous and
sedimentary rocks under go changes due to metamorphic
Igneous rocks: These rocks are formed by cooling and action of pressure and interanl heat. For example due to
solidifying of the rock masses from their molten magmatic metamorphic action grainte becomes gneiss, trap and
condition of the material of the earth. Generally igneous basalt changes to schist and laterite, lime stone changes
rocks are strong and durable. Granite, trap and basalt to marble, sand stone becomes quartizite and mud stone
are the rocks belonging to this category, Granites are becomes slate.
formed by slow cooling of the lava under thick cover on
the top. Hence they have crystalline surface. The cooling Physical Classification
of lava at the top surface of earth results into non-crystalline Based on the structure, the rocks may be classified as:
and glassy texture. Trap and basalt belong to this
category. 1. Stratified rocks 2. Unstratified rocks
Sedimentary rocks : Due to weathering action of water, Stratified rocks : These rocks are having layered
wind and frost exisitng rocks disintegrates. The structure. They posses planes of stratification or cleavage.
disintegrated material is carried by wind and water, the They can be easily split along these planes. Sand stones,
water being most powerful medium. Flowing water slate etc. are the examples of this class of stones.
deposits its suspended Materials at some points of Unstratified rocks: These rocks are not stratified. They
obstacles to its flow. These depositied layers of Materials possess crystalline and compact grains. They cannot be
Construction - D’man Civil - R.Theory For Exercise 1.2.17 85
split in to thin slab. Granite, trap, marble etc, are the 6 Acid test
examples of this type of rocks.
7 Water absorption test
Foliated Rocks : These rocks have a tendency to split
8 Smith's test
along a definite direction only. The direction need not be
parallel to each other as in case of stratified rocks. 9 Crystallization test
Chemical classification 10 Microscopic test
On the basis of their chemical composition engineers 11 Freezing and thawing test.
prefer to classify rocks as: 1 Hardness: To determine the hardness of stone
Silicious rocks, Argillaceous rocks and Calcareous rocks 2 Crushing test : To determine the maximum load at
Silicious rocks : The main content of these rocks is which stone crushes or fails while loading.
silica. They are hard and durable. Examples of such rocks 3 Impact test: To determine the toughness of a stone.
are granite,, traps and quartzines etc.
4 Fireresistance test: Determine the presence of
Argillaceous rocks: The main constituent of these rocks calcium carbonate which will produce fire
is argil i.e., clay. These stones are hard and durable but
they are brittle. They cannot withstand shock. Slates 5 Attrition test: To determine the rate of wear of stones
and laterites are examples of this type of rocks. 6 Acid test: To determine the action of acid on the stone
Calcareous rocks: The main constituent of these rocks 7 Water absorbption test : To find out the % of water
is calcium carbonate. Limestone is a calcareous rock of absorbtion of test stone.
sedimentary origin while marble is a calcareous rock of
metamorphic origin. 8 Smith’s test : Indicate the presence of earthly matter
Testing of stones 9 Crystallization test : To determine the durability or
weathering quality
To determine the suitability of stone for its use in
engineering works the following tests are performed: 10 Microscopic test: To study the mineral constituents,
grain size etc.
1 Hardness test
11 Freezing and thawing test: To determine the behavior
2 Crushing test of stone under freezing
3 Impact test
4 Fire resistance test
5 Attrition test

Table

COMMON BUILDING STONES OF INDIA

STONES ROCKS CHARACTERISTICS USES PLACES

Hard and tough; difficult to Road metal, for Maharashtra, Bihar,
Basalt work Its sp. gravity is 3 and rubble masonry, Gujarat, Bengal.
and Igneous compressive strength varies foundation work, And M.P.
Trap from 1530 to 1890 kg/cm2. etc.
Its weight varies from 1800
to 2900 kg/m3
Chalk Sedimentary Pure white limestone soft In preparing Maharashtra, Bihar,
and easy to from powder. glazier's putty: as Gujarat, Bengal. Punjab,
colouring material in Rajasthan, M.P,
manufacture of Andaman- Island
Portland cement. U.P.& H.P.
Gneiss Metamorphic Splits into thin slabs easy Street paving, rough Madras, Mysore,
to work .Its sp. Gravity is 2.69 stone masonry work, Bihar, A.P, Maharashtra,
and compressive strength is etc. Bengal, Kerala, Gujarat
2100kg/cm2.

86 Construction - D’man Civil - R.Theory For Exercise 1.2.17

STONES ROCKS CHARACTERISTICS USES PLACES

Granite Igneous Hard, durable and available in Steps, sills, facing Kashmir, Madras, Punjab,
different colours, highly walls work bridge piers, Rajasthan, U.P, M.P,
resistant to natural forces, can columns, road metal, Mysore, Assam, Bengal,
take nice polish. Its Sp. gravity ballast, etc. It is Bihar, Orissa, Kerala,
Varies from 2.6 to 2.7 and unsuitable for carving. & Gujarat.
compressive strength varies
from 770 to 1300 kg/cm2.
Its weight is about 2600 to
2700 kg/m3.
Kankar Sedimentary Impure limestone Road metal, North & central India.
manufacture of
hydraulic lime, etc.
Metamorphic Porous and spongy structure, Building stone, road Bihar, Orissa, Mysore,
easily quarried in blocks. metal, rough stone, M.P., Maharashtra,
Contains high percentage of masonry work. etc. Kerala, A.P., & Madras.
Oxide of iron; available in
different colours. Its
compressive strength various
from 18 to 32 kg/cm2.
Lime Stone Sedimentary Consist of carbonate of lime Floors steps , walls, Maharashtra, Bihar,
easy to work Its Sp. gravity road metal, manufacture Gujarat, Bengal.
various from 2.00 to 2.75 and of lime in blast Punjab, Rajasthan,
compressive strength is 550 furnace etc. M.P, Andaman- Island
kg/cm2. U.P.& H.P.
Marble Metamorphic Can take nice polish and Flooring, facing work, Maharashtra, Gujarat,
available in different coloures. Columns, steps, Rajasthan, M.P,
Its Sp. gravity is 2.65 and ornamental works etc. Mysore,
compressive strength is It can take nice polise It U.P and A.P.
720 kg/cm2. can easily be shown
and carved.
Moorum Metamorphic Decomposed laterite, Blindage for metal Bihar, Orissa, Mysore,
deep brown or red in colours. roads,for fancy paths M.P, Mah., Kerala,
and garden walls . A.P., & Madras
Quartzite Metamorphic Hard, brittle, crystalline, Retaining wall, road Madras, Punjab,
and compact, difficult to metal, concrete, U.P, Mysore, Bengal,
work and dress. aggregate, pitching, Gujarat.
rubble masonry,facing Rajasthan, A.P.
building etc.
Sand stone Sedimentary Consists of quartz and Steps, facing work Maharashtra, Bihar,
other minerals, easy to work columns, flooring walls, Gujarat, Bengal, Punjab,
&dress and available in road metal,ornamental Rajasthan, M.P,
different colours. It is Sp.gravity work etc Andaman Island,
various from 2.65 to 2.95 U.P, H.P, A.P,
and compressive strength is Kashmir, Madras .
650 kg/cm2. Its weight is
about 2000 to 2200 kg/ cm3. .
Slate Metamorphic Black colour and splits Roofing work, sills, U.P., M.P., Bihar,
along natural bedding planes, damp proof courses, Madras, Mysore
non-absorbent. Its Sp. gravity etc. and Rajasthan.
is 2.89 and compressive
strength varies from 75 to
207 N/mm².

Construction - D’man Civil - R.Theory For Exercise 1.2.17 87

6 Reconstructed stone, With respect to natural bed, the stones are placed in
different situations as follows:
7 Bituminous stone
1 Arches
Natural bed of stone
The bedding plane is kept at right angles to the resultant
1 It is the original position occupied by the sedimentary
line of thrust, from consideration of the stability of the
(stratified) rocks from which the stone is obtained. It
arch.
is also known as the plane of cleavage.
2 Cornices, string courses, etc.
2 These rocks have a distinct plane of division along
which stones can easily be split and it thus indicates The natural bed should be placed vertically and
the layer is divided into numerous thin layers or perpendicular to the face otherwise the layers of
laminations, whose planes are parallel to the plane of overhanging portions being horizontal will drop of.
the main strata.
3 Column or a wall
3 Thus, stone quarried from such rocks should be placed
In this, the load line is vertical; the stones should be placed
in a stone masonry; in such a manner that the direction
with the planes of bedding radial, so that, thrust acts
of load or pressure is at right angles to its laminations.
normal to the bedding plane.
4 Such an arrangement gives maximum strength to the
stone work.

Clay products (bricks)

Objectives: At the end of this lesson you shall be able to
• define clay products
• compare stone and brick
• explain composition of brick earth
• describe the method of manufacturing of bricks
• explain the qualities of good bricks
• classify the bricks
• state testing of bricks
• list out the special bricks.
Introduction refractory bricks, terra-cotta, porcelain, earthen-wares and
The clay occurs plenty in nature, when it is made wet stone-wares). Burning of moulded clay products makes
with water possesses a high degree of tenacity and them sufficiently strong for use as construction materials.
plasticity it can be moulded in designed shape and they Bricks: Moulded clay in rectangular block of uniform size,
dried and burnt.The clay products which are employed in shape as per standard, which is dried and burned for the
building industry are bricks, ceramic products (tiles, purposes of masonry work, is called brick.
Comparision of stone and brick
S.No. Stone Brick
1 It is heavier than brick It is lighter than stone.
2 It is obtained from rock It is made from clay.
3 Free from clay holes and flaws. Free from lumps, flaws and cracks.
4 Hard and tough Hard and sound
5 It absorbs heat more than a brick. It absorbs less heat comparatively.
6 Water absorption <5% Water absorption <16%
7 It is uniform in colour and can be Uniform in colour, shape and size.
Shaped to the desired size.
8 It has high durability. It is durability is less than that of stone.
9 Suitable for industrial area as it is Acid and smoke resistance is good but
acid and smoke proof. Less than that of stone.
10 Dressing, transporting costly. Overall cost of manufacturing is less.
11 Labour cost for laying is more. Labour cost is less

Construction - D’man Civil - R.Theory For Exercise 1.2.17 91

shown in Fig 7 may be functioning as follows: 1 Size and shape 6 Porosity
Chamber 1 - loading 2 Color 7 Strength
Chamber 2 to 5 - drying and pre-heating 3 Structural 8 Resistance of fire
Chamber 6 and 7 - Burning 4 Hardness 9 Efflorescence
Chamber 8 and 11 - Cooling 5 Soundness 10 Durability
Chamber 12 - Unloading Example
With the above arrangements the circulation of the flue 1 Colour: - Uniform copper red colour.
gas will be shown by arrows in fig 7 The cool air enters
2 Shape: - Rectangular 19 x 9 x 9 cm Standard.
through chambers 1 and 12 as their main doors are
open. After crossing the cooling chambers 8 to 11, it 3 Sound: - Sound proof, clear ringing sound when struck
enters the burning section in a heated condition. It then with each other.
moves to chambers 2 to 5 to dry and pre-heat the raw 4 Absorption:- It should not<20% for I Class <22% for
bricks. The damper of chamber 2 is in open condition II Class When socked in cold water for 24hrs
and hence, it escapes into atmosphere through chimney.
5 Toughness: - Should not be break when dropped from
The initial cost of installing this kiln is high: but it
an height of 1 meter.
possesses the following advantages:
6 Crushing Strength: - 3-5 N/mm square. Minimum.
- The bricks are burnt uniformly equally and evenly.
Hence the high percentage of good quality bricks can 7 Specific gravity - 2-2.6
be produced Classification of brick:-
- It is possible to regulate heat inside the chambers The brick can broadly be dividing into two categories as
through fuel holes. following:
- The supply of bricks is continous and regular because 1 Unburnt bricks: These brick are dried with the help of
of the fact that the top of kiln is closed and it can be sun heat only.
made to work during the entire year.
2 Burnt bricks: These brick are burnt clamp or kiln. They
- There is considerable saving in fuel due to pre-heating are classified into the following the four categories:-
of raw bricks by flue gas. Thus the hot gases are fully
utilized in drying and pre-heating the raw bricks. 1 1ST Class bricks: R.B. work, following, as blast R.C.
work arches etc.
- There is no air pollution in the locality because the
exhaust gases to not contain black smoke or coal 2 2nd Class brick: Un-important situation and for internal
dust particles. walls.
Qualities of good bricks 3 3rd Class brick: Temporary building
The good brick which are to be used for construction of 4 4th Class brick: Foundation and Floor etc.
important engineering structure should possess the Testing of bricks: Indian standards, IS: 3495-1992,
following qualities 'Method of test for burnt clay bricks, Part 1 to 4' gives
details of the tests, as follows:

Class designation Sampling Lot Test to be made

IS:3102-1071 according to their size size
compressive strength (N/ mm²)

10 20 bricks 50,000 or 1 com.strength

more 2 waterabsorption
3 efflorescence
4 dimensional test
5 hardness
6 soundness
7.5 to 3.5 20 bricks 100,00 or Test at the discretion of
more the engineer in charge.

Construction - D’man Civil - R.Theory For Exercise 1.2.17 97

The tests to be made on bricks, as given above, are 1 Specially shaped bricks
as follows
2 Heavy duty bricks
1 Absorption test: To know about the amount of water
3 Perforated bricks
absorbed of brick.
4 Burnt clay hollow bricks
2 Crushing strenght test: To know about the
compressive strength in brick 5 Sand lime bricks
3 Effloresence test: To know about the presence of 6 Sewer bricks
soluble salt in the brick. 7 Acid resistant bricks
4 Hardness test: To know the hardness of brick by figure Hollow bricks
nail.
Hollow bricks are made from clay and formed with cavities
5 Shape and size: To know the standard size and shape which module their weight.
of brick.
These bricks are used 20 mm to 25 mm thick wall. They
6 Soundness: To know about the strength of soundness. are suitable for partition wall.
7. Structure: To know about the any hole, lumps in the
The cavity reduces the transmission of sound and hoot.
brick.
The hollow bricks are machine pressed and formed cavity
Special bricks: (Fig 8) in the brick (Fig 8)
These bricks differ from the commonly used building bricks
with respect to their shape, specification and special
purpose for they are made.

98 Construction - D’man Civil - R.Theory For Exercise 1.2.17

Lime
Objectives: At the end of this lesson you shall be able to
• define lime
• classify lime
• state properties of lime
• describe uses of lime
• compare fat and hydraulic lime
• explain tests for lime
• list out the precautions in handling lime.

Introduction 6 An excellent cement and adheres to the masonry units

lime is produced from calcium carbonates in the form of perfectly
limestone, seashells, coral, kankar, etc. quicklime is not 7 Lime masonry proves durable due to low shrinkage in
a stable product. If it left exposed to air, it absorbs carbon drying.
dioxide from air and revert back to carbonate. Hence,
quick lime should be slaked to calcium hydroxide Uses of lime
(Hydrated or slaked lime) as early as possible to make 1 It is used as a matrix for concrete.
the material stable.
2 It is used as a binding material in mortars for stoneware
Definition and also in bedding and joining brickwork of low
A powder obtained by heating limestone, is called lime. strength.
Classification 3 It is used for plastering walls, ceilings, etc.
IS: 712-1973, classifies lime as follows: 4 It is employed for white washing and as a base coat
for distempers.
Class a: eminently hydraulic lime, which can be used for
structural works, such as arches, domes, etc. 5 It is used for knotting of timber work before painting.
Class b: semi-hydraulic lime which can be used for 6 It is used for production of artificial stone, lime - sand
constructing masonry. bricks, foam-silicate products, etc.
Class c: fat lime that can be used for finishing coat in 7 When mixed with Portland cement, the lime-cement
plastering, white washing, etc. or used for masonry mortar mortar attains such valuable properties, that it replaces
with addition of pozzolanic material. the costly cement plaster and serves as a plasticizer.
Class d: magnesium or dolomite lime is used for finishing 8 It is used as a flux in the manufacture of steel.
coat in plastering and whitewashing. 9 Eminently hydraulic lime can be used for masonry work
Class e: Kankar lime produced by burning lime nodules below ground level.
(found in soils like black cotton soils contain silica) is 10 It is used in the manufacture of paints.
hydraulic. It can be used for masonry mortar.
11 It is used for stabilizing the soils.
Class f: Siliceous dolomite lime is used generally for
undercoat and finishing coat of plaster. 12 It is employed for creating good sanitary conditions in
foul, damp and filthy places.
Notes:
1 Carbide lime is a by-product of manufacturing of Tests for lime: It can be classifies into two types-
acetylene. It can be used for mortar for plaster work, laboratory test and field test.
but generally it is not recommended for whitewashing Laboratory tests for building lime: Indian standards
un less procured fresh in the form of a paste before it specify ten laboratory tests for lime in IS: 6932-1973
dries up or is treated properly. 'Methods of test for building lime'.
2 Lime containing more than30percentage impurities like Field tests for building lime: IS: 6924-1974, gives a
clay is called poor limes. number of field tests for building lime, as follows:
Properties of lime 1 Visual examination: class C lime should be pure
1 Easily workable. white in colour.

2 Possesses good plasticity. 2 Hydrochloric acid test: The purpose of this test is to
assess the classification and calcium-carbonate
3 Stiffens early. content of lime.
4 Provides strength to the masonry. 3 Ball test: the purpose of this test is to assess the
5 Offers good resistance to moisture. classification.

Construction - D’man Civil - R.Theory For Exercise 1.2.17 99

 Comparison between fan lime and hydraulic limes:
S.No. Item Fat Lime Hydraulic lime
1 Composition It is obtained from It is obtained from lime stones
comparatively pure containing to the extent of
carbonate of lime about 5 to 30 % and some
containing only 5% amount of ferrous oxide.
of clayey impurities.
2 Slaking action It slakes vigorously. It slakes slowly. Its volume
Its volume is increased a slightly increased. The
to about 2 to 2 1/2 slaking is not accompanied
times the volume of by sound or heat.
quick lime. The slaking
is accompained by
sound and heat.
3 Setting action It sets slowly in It sets under water. It combines
presence of air. It with water and forms crystals
absorbs carbon dioxide of hydrated tri-calcium silicate.
from atmosphere and
forms atmosphere and
forms calcium carbonate.
4 Hydraulicity It does not possess It possesses hydraulic property.
hydraulic property.
5 Colour It is perfectly white in Its colour is not so white as fat
colour. lime.
6 Strength It is not very strong. It is strong and can therefore
Hence, it cannot be be adopted where strength is
used where strength required.
is required.
7 Uses It is used for plastering, It is used for preparing mortar for
white washing, etc. and thick walls, damp places, etc.
for preparing mortar with extreme care is required to
sand or surkhi. prepare mortar of this lime for
plaster work.

4 Impurity test: the purpose of this test is to assess 1 Contact with water: the quick lime should not be
the quality of lime. allowed to come in contact with water before slaking.
5 Plasticity test: the purpose of this test is to assess 2 Facilities for workers: goggles for eyes and respirators
the plasticity of lime for nose and throat protection, rubber gloves, gum
boots, skin protecting cream or oil and there should
6 Workability test: the purpose of this test is to assess
be provision of adequate quantity of water.
the workability of lime.
3 Fire hazard: all suitable measures should be taken to
Precautions in handling lime:
avoid chances of any fire hazard.

Cement
Objectives: At the end of this lesson you shall be able to
• define cement
• state the properties of cement
• explain uses of cement
• compare cement and lime
• state manufacturing of cement
• explain the flow diagram of the wet process of cement manufacturing
• describe types of cement
• state cement water proofer
• state Admixtures
• explain test for cement
100 Construction - D’man Civil - R.Theory For Exercise 1.2.17
Introduction 7 Preparation of foundations, watertight floors, footpaths,
etc. The comparision between cement and lime is
cement is the most important material in building
shown in Table - A
construction. This is obtained by heating a mixture of
lime and clay. Cement may be prescribed as a material
Manufacture of portland cement: (Fig 1 and Fig 2)
with adhesive and cohesive properties which must be
capable of bonding mineral fragments into a compact There are two processes employed,
whole. Cement may be classified as: (i) Natural Cement,
1 Wet process- this process is generally used if the raw
(ii) Artificial Cement.
Materials available are soft e.g. chalk and clay.
Definition
Burning: The burning is carried out in a rotary kilin as
Material obtained by burning mixture of calcareous and shown in fig 1. A rotary klin is formed of steel tubes. Its
argillaceous Materials with a small quantity of gypsum at diameter varies form 250 cm to 300cm. Its length varies
a very high temperature and pulverized into very fine powder, from 90m ti 120m. It is laid at a gradien of about 1 in 25
known as Cement. to 1 in 30. The klin is supported at intervals by columns
of massonry or concrete. The refractory lining is provided
Properties of cement
on the inside surface or rotary klin. It is so arranged that
Good cement possesses the following properties: the klin rotates at about one to three revolutions per minute
1 Provides strength to masonry. about its longitudinal axis.

2 Stiffens or hardens early. The corrected slurry is injected at the upper end of klin.
Fig 1 shows the rotary klin for the wet process. The hot
3 Possesses good plasticity. gases or flames are forced through the lower end of kiln.
4 An excellent building material. The portion of the kiln near its upper end is known as dry
zone and in this zone, the water of slurry is evaporated.
5 Easily workable. As the slurry gradually descends, there is rise in
6 Good moisture-resistant. temperatrue and in the next sectin of kiln, the carbon
dioxide from slurry is evaporated. The small lumps, known
Uses of cement: as nodules, are formed at this stage . These nodules
1 Cement mortar for masonry works, plaster, pointing, then gradually roll down passing through zones of risinhg
etc. temperatrue and ultimately reach to the burning zone,
where temperature is about 14000C to 15000C. In burning
2 Concrete for laying floors, roofs and constructing zone, the calcined product is formed and nodules are
lintels, beams, weather sheds, stairs, pillars, etc. converted into small hard dark greenish blue balls which
3 Construction of important engineering structures such are known as clinkers.
as, bridges, culverts, dams, tunnels, storage In the modern technology of dry process, the coal brought
reservoirs, light houses, docks, etc. from the coal fields is pulverised in vertical coal mill and it
4 Construction of water tanks, wells, tennis courts, is stored in silos. It is pumped with required quantity of
septic tanks, lamp posts, roads, telephone cabins, air through the burners. The preheated raw Materials roll
etc. down the kiln and get heated to such an extent that the
carbon dioxide is driven off with combusion gases. The
5 Making joints for drains, pipes, etc. material is then heated to temperature of nearly 14000C
6 Manufacture of precast pipes, piles, garden seats, to 15000C when it gets fused together. The fused product
artistically design urns, flower pots, etc., dustbins, is known as clinkers or raw cement.
fencing posts, etc.

Table - A
Comparison between cement and lime
S.No. Aspects Cement Lime
1 Colour Greenish grey. White or grayish.
2 Slaking Does not slake when wetted with water Slakes when wetted with water
3 Setting Sets rapidly when mixed with water Sets slowly when mixed with water
4 Strength Artificial cement possesses more Possesses less strength.
strength
5 Suitability Can be used for important and heavy Cannot be used for important and heavy
engineering structures engineering structures.

Construction - D’man Civil - R.Theory For Exercise 1.2.17 101

 FLOW DIAGRAM FOR WET PROCESS

Calcareous Materials
Argillaceous materials Water
(Lime stone or chalk)
(Clay, shale)

Preliminary crushing
Wash mills

Elevators Elevators
(Storage bins) (Storage bins)

Hoppers
v

v
v
Wet grinding (Ball mills)

Fire-coal

Raw slurry

Crushing & grinding

(Ball mills)
Elevators

Lime slurry
Corrections silos Pulverized coal
Clay slurry

Rotary kilns
v

Clinker

Gypsum Elevators(Clinker storage)

Gypsum hopper Clinker grinding (Cement grinding mills)

Elevator (cement silos)

Weighing, packing and despatch

102 Construction - D’man Civil - R.Theory For Exercise 1.2.17

 FLOW DIAGRAM OF DRY PROCESS

Argillaceous materials
Calcareous Materials

Crushing Crushing

Fine grinding in ball mill &

tube mill Fine grinding in ball mill

Storage Hoppers
Storage

Wet grinding (Ball mills)

Fire-coal

Raw slurry

Crushing & grinding

(Ball mills)
Elevators

Lime slurry
Corrections silos Pulverized coal
Clay slurry

Rotary kilns
v

Clinker

Gypsum Elvators(Clinker storage)

Gypsum hopper Clinker grinding (Cement grinding mills)

Elevator (cement silos)

Weighing, packing and despatch

Construction - D’man Civil - R.Theory For Exercise 1.2.17 103

The size of clinkers varies from 3mm to 20mm and they From storage tanks Coal dust
are very hot when they come out of buring zone of kiln.
The clinker temperature at the outlet of kilnis nearly 10000C
to 15000C when it gets fused together. The fused product
is known as clinkers or raw cement.
The size of clinkers varies from 3mm to 20mm adn they Rotary kiln
are very hot when they come out of buring zone of kiln.
The clinker temperature at the outlet of kin is nearly
10000C. A rotary kiln of small size is provided to cool
down the hot clinkers. It is laid in opposite direction as
Formation of clinkers
shown in Fig 1 and the cooled clinkers having temperature
of about 950C are collected in containers of suitable sizes.
Grinding : The clinkers as obtianed from the rotary kiln
are finely ground in ball mills and tube mills. During
grinding a small quantity about 3 to 4 percent of gypsum Gypsum Coolers
is added. The gypsum controls the initial setting time of
cement. If gypsum is not added,the cement would set as
soon as water is added. The gypsum acts as a retarder
and it delays the setting action of cement. It thus permits
cement to be mixed with the aggregate and tobe placed Grinding of clinkers in ball
in position. mills and tube Mills

The grinding of clinkers in modern plants is carried out in

the cement mill which contains chromium steel balls of
various sizes. These balls roll within the mill and grind
the mixture which is collected in a hopper and taken in Storage in silos
the bucket elevator for storage in silos. The cement from
silos is fed to the packer machines. Most of the modern
plants have electric packing plant having provision plan to
account for the weights of empty bags of different types
and to ensure a 50kg net weight of cement bag within Weighing and packing in bags
+200g3 limit . Each bag of cement contains 50kg or about
0.035m 3 of cement. These bags are automatically
discharged from the packer to the conveyoyur belts to
different loading area. They are carefully stored in a dry
Distribution
place Fig 1 shows the flow diagram of buring and grinding
operations.
Flow diagram of burning and grinding operations Dry process : this is usually employed where the raw
of cement materials are hard such as cement rock or blast furnace
Packing of cement : The packing of cement is mostly slag. adopted in most of the cement industries, due to-
done in our country in conventional jute or gunny bags. • For dry process the heat required per kg of clinker
These bags have proved to be satifactory containers as produced is less.
their shape and size make them convenient to handle. If
the properly handled, they may make three to five trips • The blending of dry powders has now perfected and
form the factory to the cement users. However the main the wet process which requires much higher
drawbacks of such type of packing are as follows: consumption of power can be replaced with confidence.

At every point of handling some portion of cement • The application of modern technology has made the
contained in jute bag is wasted. production of cement by dry process more economical
and of superior quality.
Even after emptying the cement bag, small quantity of
cement remains in the bag and it is thus not possible to • Both the processes involve the following steps:
take advantage of the full contents of the bag. • Collection of raw materials.
Such type of packing leads to the air pollution. • Crushing, grinding and mixing of raw materials.
The handling of jute bags proves harmful to the healthy of • Burning.
labourer also as he inhales a considerable amount of
cement particles during the transport of such bags. • Grinding of clinker.(Fig 2)

The quality of cement is affected due to entry of moisture

from the atmosphere.

104 Construction - D’man Civil - R.Theory For Exercise 1.2.17

Ball mill (Fig 2) a) IS: 1489 (Part-I)-1991 (fly ash -based)
TYPES OF CEMENT b) IS: 1489 (Part-II)-1991 (calcined clay-based)
Cement is specified by its grade (compressive strength 3 Sulphate-resisting cement-IS: 12330-1988
of 1:3 cement mortars as cubes of 50 cm² areas (7.06
cm) in 28 days for defining strength) thus, Grade-33 4 Portland slag cement-IS:455-1989 (PSC)
cement (C-33) means cement with standard mortar cube 5 Low- heat cement-IS: 12600-1989
strength of 33 N/ mm² in 28 days. Only the grade of the
cement is marked on the bags of 50 kg., 6 Rapid-hardening cement-IS:8041-1990
7 Concrete sleeper-grade cement-IS: T40-1985
8 Coloured cement-white cement-IS: 8042-1989
9 Oil well cement-IS: 8229-1986
10 Hydrophobic cement-IS: 8043-1991
11 Masonry cement-IS: 3466-1988
12 High-alumina cement-IS: 6452-1989
13 Super-sulphated cement-IS: 6909-1990
14 Expansive cement
15 Quick setting cement
CEMENT WATER PROOFERS
The water proofers are required for all water retaining
structures especially for:
The following are the IS specifications: i) Swimming pools
1. Ordinary Portland cement (OPC) in 3 grades, ii) Basements
a) Grade 33 - IS: 269-1989 designated as C-33, iii) Hospitals
b) Grade 43 - IS: 269-1989 designated as C-43, iv) Refrigeration rooms
c) Grade 53 - IS: 269-1989 designated as C-53 v) Cold storages
2. Portland pozzolana cement (PPC) (a mixture of OPC vi) Water supply and sewage works
and Pozzolana)
Construction - D’man Civil - R.Theory For Exercise 1.2.17 105
vii) Exterior plaster compressive strength. Vicat apparatus is used for this
test.
viii)Bath rooms and kitchens
4 Setting times-To know the initial and final setting times.
ix) Reservoir
Vicat apparatus is used for this purpose.
These water proofers render mortar or concrete water tight
5 Soundness -To find out the presence of free lime. Le
either by filling the pores physically or reacting chemically.
chatelier apparatus is used for this purpose.
The water proofer may be in powder, paste or liquid form.
The amount to be added must be in accordance with the Field tests may be carried out to ascertain roughly the
instructions of the manufactures; generally the following quality of cement:
proportions are used:
1 Colour-Greenish grey
" 2 to 5 %.......when in powder form
2 Presence of lumps, -Pressed between the thumb and
" 1part paste and 10 parts water…when in paste form fore finger it should be powdered.
" 1 litre liquid and 15 litres water….when in liquid form 3 Rubbing-When rubbed between the fingers it should
feel smooth.
ADD MIXTURES
4 When a hand full of cement thrown into a bucket of
These are the Materials which are added in cement mortar
water it floats.
or concrete to improve upon their quality. The admixtures
serve the following purposes: 5 One should feel cold when a hand is insert in to a bag
of cement.
1 Improve the workability
Grades of cement
2 Retard setting action of the mortar and concrete.
The bureau of Indian Standards has classified in three
3 Increase the bond strength between reinforcement and
different grades
concrete.
i 33 grads
4 Improve the water proofing properties of the cement
mortar or concrete. ii 43 grade
5 Reduce shrinkage during setting of mortar or concrete. iii 53 grade
6 Reduce bleeding and segregating effect of concrete. The grade number indicates the compressive strength of
cement sand mortar in N/mm2 at 28 days
TESTS FOR CEMENT
Properties of cement
The properties of concrete or mortar largely depend upon
the quality of cement used. The quality of cement can be • Provides strength to masonry
tested in the laboratory by the following tests based on
• Stiffens or hardens early
Indian Standard Specification (IS: 269-1958):
• Possesses good plasticity
1 Fineness-To know the fineness of grinding.
• An excellent building material
2 Compressive strength-Cement cubes are prepared and
tested after 3,7 and 28 days of curing. • Easily workable
3 Consistency-to know the quantity of water to be added • Good moisture resistant
for testing the cement for setting time, soundness and

S.No. Types Features Uses

1 Ordinary portland cement General concrete structures Medium rate of strength developed
less resistance to chemcial attack
2 Acid resistant cement Acid resistant heat resistant It cannot resist the action of water
coating of installation of well
chemical industry
3 Rapid hardening portland Rapid strength is developed Curing period short, burnt at high
cement temperature
4 Blast furnance cement Mass concrete structure Initial setting time not less than 30
minutes, final setting time 10 Hrs
5 Expading cement Construction of water retaining
structures repairing the damaged
concrete structures

106 Construction - D’man Civil - R.Theory For Exercise 1.2.17

S.No. Types Features Uses
6 Coloured cement Finishing of floors, external By adding 5 to 15% of suitable
surface artificial marble, stair colouring pigment before the cement
tread is finally ground.

7 High alumina cement For works in chemical plant It is completely resistant to the
and furnaces action of surface

8 Hydrophobic cement Frost resistant and water Initial stage the gain in strength is
resistant less

9 Modified portland cement Heavy construction of heavy Less heat of hydration

abutment, large piers, retaining
wall etc
10 Extra rapid hardening cement Suitable for cold weathering Qty of calcium chloride should not
concrete exceed 3 percentage
11 Sulphate resisting Used at places where sulphate
portland cement action is severe.

Port land - pozzolana cement (IS:1489) • It free lime is removed, the pozzolana concrete have
a greatly resistance to chemical agencies and also
• This cement is made either by intergrading port land
resist the sea work better than ordinary cement.
cement clinker and pozzolana or by uniformly blending
port land cement and fine prozzolana. • Pozzolana cement is popularly used in the
construction of dam.
• The pozzolana cement contain varies from 10 to 25%
by weight of cement. • Pozzolana cement manufactured in burnt clay or
shade or fly ash.
• Pozzolana does not possess cementing value
themselves but any how the property of combining with The following table shows the compressive strengths
the lime which possess cementing property. reduces by ordinary portioned cement and port land
pozzolana cement.

Table
Compressive strength of port land pozzolana cement and ordinary port land cement
Age in days Compressive strength
Ordinary port land cement Port land Pozzolana cement
2 2
1 77 Kg/cm - 8 N/mm 77 Kg/Cm2 - 8 N/mm2
3 192 Kg/cm2 - 19 N/mm2 165 Kg/cm2 - 16 N/mm2
7 256 Kg/cm2 - 26 N/mm2 247 Kg/cm2 - 25 N/mm2
14 310 Kg/cm2 - 31 N /mm2 301 Kg/cm2 - 30 N /mm2
15 375 Kg/cm2 - 38 N /mm2 375 Kg/cm2 - 38 N /mm2

Construction - D’man Civil - R.Theory For Exercise 1.2.17 107

Construction
Draughtsman Civil - Basic Engineering Drawing R. T. for Exercise 1.2.20

Sand
Objectives: At the end of this lesson you shall be able to
• define sand
• state the characteristics of sand
• state the type of sand
• state uses of sand.

Sand 3 Sea sand

• Sand particles consists of small grains of silica. • This sand is obtained from sea shore.
• Sand is formed by decomposition of sand stone due • Sea sand consists fine rounded grains like river sand
to various effects of weather. Decording to the material
sources sand is obtained. Artificial sand is prepared • The colour of sea sand is light brown.
by crushing stones and gravel to powder. • Sea sand contains salts.
Characteristics of good sand • The salts absorb moisture from the atmosphere and
1 Sand should be clean and free from coatings of clay causes dampross, efflorescence and disintegration of
and silt. work.
2 Sand should be free from salt • Sea sand retorts the setting action of cement
3 Sand should be coarse, angular, hard and sharp grows • Due to above reason, to avoid the use of sea sand for
engineering works.
4 Sand should not contain organic matter.
Classification of sand according to the size of grains
5 It should be strong and durable
1 Fine sand
6 It should be chemically inert.
2 Coarse sand
7 Sand should pass through 40.75 mm sieve and entirely
retained on is sieve of 75 micron 3 Gravelly sand
Types of sand 1 Fine sand
There are three types of sand • Sand passing through a sieve with clear opening of
1.5875 mm is known as fine sand. This sand is used
1 Pit sand for plastering.
2 River sand 2 Coarse sand
3 Sea sand • Sand passing through a sieve with clear opening of
1 Pit sand 3.175 mm is known as coarse sand. This sand is used
for masonry work.
• Pit sand is found as deposits in soil
3 Gravelly sand
• It is obtained by forming pits into soils.
• Sand passing through a sieve with clear opening of
• Sand is excavated from a depth of about 1 m to 2 m 7.62 mm is known as gravelly sand. This sand is used
from the ground level. for concrete work.
• Pit sand consists of sharp, angular grains and also Bulking of sand
free from salts.
• The presence of moisture is sand increases the volume
• For preparing mortar, clean the pit sand free from
of sand is called bulking of said.
organic matter.
Uses of sand
2 River sand
• Sand is used as binding materials to make the mortar
• River sand is obtained from bed of rivers
economical.
• River sand consists of fine round grains • It is used for making mortar and concrete
• Colour of sand is almost white. • Sand helps in early setting of mortar
• River sand is available in clean condition • Sand increases the density of mortar
• This sand is used for purposes • Sand is used to fill the basement.

151
Construction
Draughtsman Civil - Basic Engineering Drawing R. T. for Exercise 1.2.21

Clay products (Tiles)

Objectives: At the end of this lesson you shall be able to
• define ceramic
• state clay for ceramic
• explain technical terms of ceramic products
• classify and describe the tiles.

Introduction 6 Common clay roof tiles

Ceramic means the technology and the art of making 7 Country roof tiles
objects with clay and similar Materials by treating with
fire. Clay products, refractories and glass come under (Encaustic tiles are the tiles initially painted with colours
this. As tiles in various forms are the principal ceramic and the colours get fixed to the tiles with heat)
products used in building. Clay floor tiles:
Clay for ceramic: There are generally salt glazed to give a good appearance.
The special ceramic product requires its own type of Floors made of these tiles, unlike cement floors, are more
special clay, even though ordinary earthenware's can be suitable for walking barefooted.
made from many types of ordinary clay. Fine white clay Clay terracing tiles: These tiles are to be made
is required to manufacture porcelain articles. Refractory according to IS: 2690-1964.
clay, which is special heat-resisting clay, is necessary
Clay ceiling tiles:
for making refractories for chimney and ovens.
(IS: 1464-1959) these tiles are usually placed on reepers,
Technical terms:
over these ceiling tiles, Mangalore tiles are laid. They are
1 Earthenware: Ordinary cooking pots and pans generally given a floor pattern decoration on the exposed
usually used in village come under this. faces.
2 Stoneware: It is a product of refractory clay. Stoneware Glazed ceramic tiles:
jars are very popular. Earthenware and stoneware
These tiles were exclusively used as wall tiles for
together is called pottery.
bathrooms in hospitals etc. large size with thick glazing
3 Porcelain: Dinner plates, tea cups and saucers come are being used for flooring in offices, airports, etc.
under this category.
Fully-vitrified tiles:
4 Terracotta: It is a hard brownish, unglazed vitrified
These tiles bridge the gap between ordinary ceramic tiles
ceramic material used for architectural ornamentation.
and marble floors. These tiles are especially used in
5 Faience: It is a city in Italy. It is earthenware or pottery kitchen floors as ordinary ceramic tiles are brittle and the
to which heavy glazing has been applied and fired. It full of any heavy object is liable to chip the ceramic tiles.
differs from porcelain. Faience has a porous shell and
Porcelain tiles:
porcelain a solid shell.
These are available in many forms as plain, coloured and
6 Glazing: The provision of a transparent or opaque
also with decorative patterns and sizes. They are rather
glass like coating is called glazing. It improves the
expensive compared to the traditional floors.
appearance, provides a smooth surface and protects
the surface from atmospheric as well as chemical Common clay roof tiles:
action.
There are many types of clay roof tiles. They are mostly
7 Tiles: It is a thin slab of baked clay of different shapes used for covering sloped roofs, e.g.,
and sizes. Terrazzo tiles made of concrete and rubber
1 Mangalore pattern roofing tiles(Fig 1)
tiles made of rubber to be used on floors and clay tiles
to be used on roofs and floors. 2 Half round country tiles (Spanish tiles)(Fig 2)
Classification of tiles: 3 Allahabad tiles (Italian tiles)(Fig 3)
1 Common clay tiles for floors Mangalore pattern roofing tiles(Fig.1)
2 Clay tiles for terraces (IS: 654-1972) These are available in various shape and
dimensions. They overlap on the tile below and also lock
3 Clay tiles for ceiling
with the adjacent tile.
4 Glazed tiles for floors and walls
5 Vitrified tiles
152
 Neutral refractory materials
Sl.No. Name Properties Uses
1 Bauxite It is mixed with clay and finely ground. It is used for preparing fire-bricks
Its melting point is 12000C. It is an containing more percentage of silica.
amosphous substance with dirty-white,
brown or reddish-brown colour.
2 Carbon It is available in three forms-amorphous It is used as activated carbon,
carbon, graphite and diamond. Its absorbent, catalyst, etc. It is also used
melting point is 35000C as lining material for furnaces.
3 Chromite It is the oxide of iron and chromium. It is the most powerful neutral refractory
Its melting point is 21800C material.
4 Forsterite It does not spall easily and it maintains It is widely used in the furnance for
well its volume at high temperature. melting copper.
Its melting point is 18900C

Mortar & concrete

Objectives: At the end of this lesson you shall be able to
• define mortar
• describe ingredients of mortar
• state the functions of mortar
• explain properties of good mortar
• List out the uses of mortar.
• State the types of mortar
• State preparation of mortar
• List out the tests for mortar
• Select the mortars for different engineering works.

Inroduction • It provides a durable / weather resisting layer between

different course of masonry in the structure.
For construction of buildings, nowadays, we mostly use
cement mortar and cement plasters. A large amount of • It forms a homogeneous mass of the structure so that
cement is consumed for these works. The total it may resist all the loads coming over it and transfer
consumption is about 3 bags per square metre of plinth the same uniformly to its foundation.
area in residential buildings and about 4 bags per square • It does pointing or plastering to the structure.
metre of plinth area in office buildings of this a major part
is used for making mortar and plasters. Properties of a good mortar
Definition • It should be capable of developing good adhesion with
the building units.
A paste formed by the addition of water to a mixture
composed of an aggregate such as sand and a matrix or • It should be easily workable
binding material like lime or cement is called mortar. • It should be cheap.
Ingredients of mortar: • It should be durable
1 Binding or cementing materials…..such as cement or • It should be capable of resisting penetration of rain
lime water
2 Fine aggregates……………such as sand, surkhi, • It should be capable of developing the design stresses.
ashes, cinder, etc.
• It should be durable and should not affect the durability
3 Water…………………should be free from oils, acids, of other materials.
alklies and other inorganic impurities.
• The joints formed by mortar should not develop cracks
Functions of mortar and they should be able to maintain their appearance
• It's binds together stones or bricks properly. for quite a long period.
• In any concrete, it holds coarse aggregates together. Uses of mortar
• In stone masonry and brick masonry, it fills up empty 1 To bind the building units such as bricks, stones, etc.
joints; a thin liquid mortar used for such purposes is into a solid mass.
termed as grout. 2 To carry out pointing and plaster work on exposed
surfaces of masonry.
156 Construction - D’man Civil - R.Theory For Exercise 1.2.21
3 It is employed for moulding purposes.
4 It is used to form joints of pipes.
5 It is used to improve general appearance of structure.
6 It is used to hide open joints of a masonry work.
7 It is used as a matrix in concrete.
Preparation of mortar(Fig 1)
It may prepare by Hand mixing or Machine mixing. When
a small quantity of mortar required, hand mixing method
is adopted. When large quantity of mortar is required
continuously at a fast rate, it is prepared by mixing of the
ingredients in mechanical mixtures.
In order to test the quantity of mortar, the following tests
are usually conducted:
1. Adhesiveness to building units test. 3. Tensile strength test.
2. Crushing strength test. 4. Setting time test

SELECTION OF MORTARS FOR DIFFERENT ENGINEERING WORKS

S. No. Nature of Work Mortar - Type and Composition
1 Thick joints in stone masonry Hydraulic time sand mortar (1:2:3)
2 Stone masonry in foundations and 1:2 fat lime surkhi mortar or 1 part lime, 1
superstructure of ordinary buildings. part surkhi and 1 part sand.
3 Brickwork in arches, plastering inside of walls. 1:5 to 1:6 cement mortar, or lime surkhi
mortar (1:2) or lime, surkhi and sand. (1:1:1)mortar.
4 Reinforced brickwork. 1:3 cement mortar.
5 Mass concrete in foundations, paving tiles, cavity 1:4 cement sand mortar or 1:2 to 3hydraulic
walls, plastering of ceiling and external plastering lime mortar.
work etc., where good finish is required.
6 Massive work below ground level especially in 1:3 cement sand mortar or 1:3 lime (eminently
water logged areas. hydraulic) sand mortar.
7 Massive works, dams, retaining walls, damp 1:3 cement sand mortar.
proofing, flooring, etc. where very high finish
is required.
8 Pointing work 1:1 to 1:2 cement sand mortar.
9 General R.C.C. works such as slabs, beams and 1:2 cement sand mortar.
columns cement concrete flooring etc
10 Damp proof course and cement concrete roads. 1:2 cement sand mortar.
11 R.C.C tanks and other retaining structures etc. 1:1½ cement sand mortar.
12 Highly stressed numbers of structure 1:1 cement sand mortar.
13 Laying fire-bricks. Fire- resisting, mortar consisting of 1 part of
luminous cement to 2 parts of finely crushed
of fire-bricks.

Substitute for sand

where the place of work they should used the stone dust.
In place of sand attain materila such as stones screenings The surkhi is the popular substitute for sand. It is obtained
burned clay or sunkhi ashes from coal, coke dust it may by finally grinding burned clay it is clean and face from
be used to prepaie mortor, The steps screenings are any impurities. It gives strength and improves hydraulic
obtained by screening crushed stones. They are sharp property of mortor. Mortar with surkhi should not be used
and impart more strength to the mortor. They are generally for external plaster or pointing work etc it disintegrates
used in big construction projects like concrete dams, under the action of air and humididty.
bridges etc. Where sand in high quantities is not available
Construction - D’man Civil - R.Theory For Exercise 1.2.21 157
Construction
Draughtsman Civil - Masonry R. T. for Exercise 1.3.22

Timber and wood products

Objectives: At the end of this lesson you shall be able to
• define timber
• classify trees
• explain and indicate the parts of structure of trees
• describe the process of seasoning
• list out the qualities and uses of timber
• explain wood based products.

Introduction ii) Endogenous trees. e.g. canes, bamboos, palms, etc.

Wood used for structural purposes is known as timber. Structure and growth of tree (Fig 1)
There is a lot of demand for primary species of timber
like, teak, deodhar, sissco, sal, etc. Basically, a tree consists of the following three parts;
(i) Trunk, (ii) crown, (iii) roots.
In order to enhance and economize the utilization of wood,
many wood-based products have been developed in a big The trunk supports the crown and supplies water and
way like veneers, plywood, hard board, particle board, nutrients from the roots to the leaves through branches
etc. and from the leaves back to the roots.

Definition The roots are meant to implant the trees in the soil, to
absorb moisture and the mineral substances it contains
The products of wood from felled trees suitable for and to supply them to the trunk
construction purposes are called Timber.
Seasoning of timber
Classification of trees
When a tree is newly felled it contains about 50% or more
According to their manner of growth, the tree may be of its own dry weight as water. The water is in the form of
divided into two main classes; sap and moisture.
i) Exogenous tree, (a) Conifer or evergreen trees,(soft It is the process of drying timber or removing moisture or
wood) (b) Deciduous or broad-leaf trees.(hard wood) sap, present in a freshly felled timber, under more or less
e.g. Deodar, chir, Kail, shishum, teak, etc. controlled conditions.

Object of seasoning of timber To maintain the shape and size of the components of the
To allow timber to burn readily if used as fuel timber articels

To decrease the weight of timber and there by to lower To make timber easily workable and to facilitate
the cost of transport and handling operations during conversion

To impart hardness stiffness strength and electrical To make timber fit for receiving treatment of paints
resistance to timber. preservatives, varnishes etc.

166
Construction
Draughtsman Civil - Masonry R. T. for Exercise 1.3.23

Protective Material - Paints & Varnishes

Objectives: At the end of this lesson you shall be able to
• define timber
• classify trees
• explain and indicate the parts of structure of trees
• describe the process of seasoning
• list out the qualities and uses of timber
• explain wood based products.

Protective Material Base

Introduction A base is a solid substance is a fine state of division and
One of the broadly classfication of building Materials is it forms the bulk of paint. It determine character of paint
protective materials. Protective of a structure is a main and it imparts durability to painted surface.
necessity. Apperance is also main factor. Final finishings Commonly used bases are
are required for all surfaces such as walls, ceilings, wood
works, metal works etc. White lead Red lead Zinc white

Definition Oxide of iron Titanium white Aluminium white

The Materials are used for the protective the surface of Lithophone Antimony white
structure are known as protective materials. Vehicle or carrier
Types of Materials used Vehicle are liquid substance which hold the ingredients
Paint of a paint in a liquid suspension.Vehicles employed are

Varnish Linseed oil Poppy oil Tung oil Nut oil

Distemper Driers

White wash These are substance accelerate the process of drying.

Drier absorb oxygen from air and transfer it to linseed oil
Colour wash which gets hardened. Some of the driers
Termite proof materials a)Litharge b)Red lead c)Sulphate of Manganese
Paint Colouring pigments
The paint are coating of fluid material and they are applied Colouring pigments gives desired colour besides the base.
over the surface of timber and metal.
Pigments are Graphite lamp black
Characteristics of an ideal paint
Indigo Pressian blue
It should posses good spreading power
Umber
It should be fairly cheap and economical
Chrome green
It can easily and freely applied
Copper sulphate
It should dry in reasonable time
Solvent
Colour should last for a long time
The function of solvent is to make the paint thin so that it
It should hard and durable can easily applied on the surface. It helps the paint to
Ingredients of oil borne paints penerate through the porous surface. The most commonly
used solvents is spirit ot turpentine.
A base
Types of paint
A vehicle or carrier
Aluminium - Gas tank, hot water pipes , radiater oil tank
Drier
Anti corrosive paint - An corroisive metal - iron
Colouring pigment
Asbestos paint - Acidic gases and steam
A solvent
Bituminous paint - Iron work under water

176
Cellulose paint- Surface contact with high cold and heat Solvent - boiled oil, spirit of wine, turpentine wood naphta
Cement paint- Plastered surface Types of varnish
Colloidal paint - Walls Depending upon solvent varnishes are :
Emulsion paint - Wood, metal, plastered surface Oil varnish
Enamel paint- Wall surface, wood, metal Spirit varnish
Graphite paint- Iron surface contact with ammonia, clorine Turpentine varnish
sulphar gas etc, mines and under ground railway
Water varnish
Inodorous paint
Distemper
Luminous paint - Dials of watch
The main ingredients are whiting or chalk and water and
Oil paint - Redecorate the surface glue or casein. It provides a smooth to plastered surface.
They are available in market under different trade names
Plastic paint- Show room auditorium
and varity of colours. They are cheaper than paint and
Varnish varnish.
The term varnish in used to indicate the solution of resinous White wash
substance prepard either in alcohal, oil or turpentine.
It contains fresh lime, water, and gum lime is toxic for
Characteristics germs. It reflects light and increase brightness of surface.
It should not shrink or show cracks after drying It is used interior wall and ceilling.

The protecting film develped by varnish should be tough , Colour wash

hard and durable It prepared by adding colouring pigment to white
It should dry rapidly wash.Applied on outer wall and inner wall.

It should not fade Termite proof materials

Ingredients Termite are white ants found in abundance in tropical and

subtropical countries. They are very fast in eating wood,
Resins or resinous substance cellulosic and non-cellulosic materials. The treatment
Driers which is given to prevent or control the growth of termites
in a building is known as termite proofing.
Solvents
Type of Termites
Resins- Copal, lac or shellac and rosin amber mastic
gum, dammar etc. Dry Wood termites - in humid coastal regin.

Driers - Litharge, white copper and lead acetate Subterranean termites - in connection with soil.

Metal and alloys

Objectives: At the end of this lesson you shall be able to
• state Types of steel reinforcement.
• describe steel for pre-stressed concrete
• identify the types of rolled steel sections.

Metals and Alloys Ferrous metals

Introduction Main element of ferrous metals iron, the iron ores are
compound of iron with non-metallic elements and certain
Metals are employed for various engineering purposes
impurities such as carbon, manganese, phosphorous,
such as structural members, roofing materials, damp proof
silicon and sulphur. Important varities of iron ore are
course, pipes, tanks, doors, windows etc.
Haematite, limonite, magnetite pyrite and siderite.
Definition
Non-ferrous metals
The substance which are extracted from ores through
The metal which do not contain iron ores as main
various refining method are called metals
constituent are called non ferrous metals.
Classification of metals
Types of ferrous metals
Metals are classified into two
• Pig iron
Ferrous metals
• Cast iron
Non ferrous metals
• Wrought iron
Construction - D’ man civil - R.Theory For Exercise 1.3.23 177
• Steel
TYPES OF STEEL REINFORCEMENT:
Steel rods used for reinforcement concrete work should
be of specified tensile strength, and they should develop
good bond strengths with concrete. There are different
types of steel, like, mild steel, tor-steel, TMT bars, etc.;
and one should be able to identify them by sight. Steel
rods of different diameters are used for R.C. work. In order
to identify the sizes easily, only standard sizes should
be used in building units. The following types of bars are
commonly used in reinforced concrete construction.
1 Hot rolled bars, there are four types,
(i) Hot rolled plain round mild steel bars (MS bars);
(ii) Hot rolled ribbed mild steel bars (generally not
recommended for use);(iii) Hot rolled high strength
deformed bars (bars like Tistrong bars by Tisco) also
called as HYSD bars (high strength got by micro
alloying).(Fig 1)
2 Hot rolled cold twisted deformed bars like Tor steel
(CTD) bars (high strength got by cold twisting) (Fig 2)

Market forms of Steel

SNo. Form of Steel Types Uses
1 Angle section Equal angle section unequal angle Structural steel work
section
2 Channel section Junior channel (ISJC) Structural member
Medium channel(ISMC)
3 Corrugated sheets G.I. Sheets Roof covering
4 Expanded sheets Reinforcing concrete in foundations,
roads, floors, bidges lathing material
partions
5 Flat bars Width 10mm to 400mm and thickness Steel grill works
3mm to 40mm
6 I Sections Junior beams (ISJB) Light beams Suitable for beams lintels, columns
(ISLB)medium beams (ISMB)wide etc
flange beams (ISWB)Heavy beams
(ISHB)
7 Plates Thickness 5mm to 50mm Structural steel work
8 Ribbed torsteel Dia 6mm to 50mm Reinforcement in concrete structure
9 Round bars Dia 5mm to 250mm Reinforcement in concrete structures
and for steel grill work
10 Square bars Side 5mm to 250mm Construction of steel grill work
11 T Sections Steel roof truss and for built up section
12 Miscellaneous Acute angle sections, Obtuse angle Structural steel work.
section sections, rail section, trough section,
Z section

3 Thermo-mechanically Treated (TMT) bars (high strength in engineering field are

got by controlled cooling) • Aluminium • Cobalt • Copper
4 Cold drawn steel wire fabric (welded wire fabric) • Lead • Manganese • Nickel
Types of non ferrous metals • Tin • Zinc
Following are the right non-ferrous metals which are sued
178 Construction - D’ man civil - R.Theory For Exercise 1.3.23
Alloys Gun metal Copper - 88%
Definition Tin - 10%
Alloys is an intimate mixture of two or more metals Zinc - 2%
Process of making alloys Dow metal
• The more infusible metal melted fast in fire clay crucible Magnesium - 88%
• The other metals then added subsequently in order to Aluminium - 12%
their infusibility.
Manganese - 0.1%
• The contents are continuously stirred to form a
Nickel silver or german silver
homogeneous mass
Copper - 50 to 80%
• The molten mixture is cast in suitable moulds and
allowed to cool. Tin - 10 to 30%
• The product obtained is called alloy Zinc - 20 to 30%
• The metal which is present in the alloy in largest Steel Alloys
proportion is called base material and the other metals
Chrome - molybdenum steel
are called alloying elements.
Chrome - nickel stainless steel
Important Alloys
Chrome - nickel steel
Duralumin : This is the important alloy of aluminium
Chromium steel
Aluminium - 94%
Chromium - vanadium steel
Copper - 4%
Cobalt steel
Manganese - 0.5 %
Copper steel
Magnessium - 0.5 %
Manganese steel
Silicon - 0.5%
Molybdenum steel
Iron - 0.5%
Nickel - chromium- molybdenum steel
Brass : This is an alloy of copper and zinc
Nickel steel
Copper - 60%
Tungsten steel
Zinc - 40%
Vanadium steel
Bronze : This is an alloy of copper and tin
Nickel -molybdenum steel
Bell metal Copper - 82%
tin - 18%
Plastics
Objectives: At the end of this lesson you shall be able to
• explain briefly the history of plastic
• state the composition of plastic
• define polymerization
• state the classification of pasties and explain
• state the moulding compounds of plastic and fabrication process involved in the fabrication of plastics
• explain properties of plastics
• state the use of plastics
• pvc pies and pipes of other materials and advantages of PVC pipes.
Brief history of plastic
1 The main objective of the first stage of development
Plastic is one of the recent engineering material which is was mainly to initiate or copy the natural plastics. In
available in the market all over the world. After the long 1865 camphor and alcohol mixed with nitro-cellulose,
research by the scientists the birth of plastic in industry and the result of the product is known as parasite,
took place in the 19th century. which is the name of the scientist. This is used for
gear wheels, dory knobs etc.
The development of plastic industry may be grouped into
three stages. 2 The second stage is comprised in first twenty years
or so of this century. In this stage the plastic industry
scientifically scrutinized and local foundation for further
Construction - D’ man civil - R.Theory For Exercise 1.3.23 179
 scientific development in this field. In 1909 1 Behaviour with respect to heating
Dr.L.Bakeland invented a product named as Bakelite
According to this classification plastics are divided into
which was found to be strong and hard material.
two groups.
3 The final stage includes present trend and its main
1 Thermo plastic
aim was improving the old plastic and producing new
varieties of plastics. In 1924 the scientist pollats 2 Thermo setting
prepared a produce from urea and formaldehyde. It 1 Thermo- plastic
was transparent like glass, and it was un breakable.
The same was produced in different attractive colours. The thermo plaster or heat non - convertible group is the
general term applied to plastics which become soft when
Composition : Plastic is organic substance and it consists heated and hard when cooled. The process of softening
of natural or synthetic benders or without moulding and hardening may be repeated for an indefinite time,
compounds. In general plastics are compounds of carbon provided the temperature during heat is not so high as to
with other elements like hydrogen, nitrogen of carbon and cause chemical decomposition. So it is possible to shape
oxygen. and reshape these plastics by means by heat and
The finished product of plastic is rigid and stable at normal temperature. The advantage of this variety plastics is that
temperature, plastics are organic substances and they the scrap obtained from old and worn-out articles can be
can flam when required heat and pressure are applied at effectively used again.
the same stage of manufacture. 2 Thermo setting
Polymerization : The substance containing of one The thermo setting or heat convertible group is the term
primary chemical are known as monomers or monoliths. applied to plastics which be come rigid when moulded at
They are synthesized to form polymers by the process a suitable temperature and pressure. When they are
known as polymerization. The properties like strength, heated in temperature ranging 127° to 177°C, It sets
rigidity, elasticity are unproved by polymerization. permanently and further application of heat does not alter
The following are the two methods of polymerization. their from or soften. But at 343°C charring occurs. This
charring is a peculiar characteristic of organic substances.
1 Addition polymerization
The thermo setting plastics are soluble in alcohol and in
2 Condensation polymerization.
certain organic solvents, when they are in thermo plastic
1 Addition polymerization stage. This property is used for making paints and
varnishes.
In this method, different molecules join together, and the
molecular weight of the resulting polymer is equal to the The thermo plastics are durable strong and hard. They
some of the molecular weight of the reacting molecular. are available in many beautiful colours. They are mainly
This process involves three stages. applied in engineering application plastics.
i Beginning of the process 2 Structure : As per classification, plastics are
divided into two groups.
ii Expansion of the chain
1 Homogeneous plastic
iii End process
2 Heterogeneous plastic
The polymers obtained in this method are polyethylene,
polypropylene, polyvinylchloride, polystyrene, 1 Homogeneous plastic
polyarcylates etc.
The plastics of this group contains carbon atoms and
2 Condensation polymerization they exhibits homogeneous structure.
In this method, low molecular substances are removed 2 Heterogeneous plastic
from high molecular substances formed from a large
In this plastic it contains carbon and oxygen, nitrogen
number of identical or different molecular. The reaction
and other elements and they exhibit Heterogeneous
proceeds with an evolution of ammonia, hydrogen chloride
structure.
and similar other low molecular substances.
3 Physical and mechanical properties
The polymers obtained by this method are phenol
formaldehyde, carbonate, melamide*, melamine According to this, plastics are divided into four groups.
formaldehyde etc. i Rigid plastics
Classification of plastics ii Semi- rigid plastics
They are classified according to their: iii Soft plastics
1 Behaviour with respect to heating iv Elastomers
2 Structure and
3 Physical and mechanical properties

180 Construction - D’ man civil - R.Theory For Exercise 1.3.23

i Rigid plastics vi Vinyl
These plastics possess a high modulus of elasticity and It is prepared by passing acetylene gas through acetic
they retain their slope under exterior stresses applied at acid or dry hydrogen chloride. It is used for wire and cable
normal or moderately increased temperature. for coatings polyethylene is a vinyl resin which is tough
and flexible and used for cable causing.
ii Semi-rigid plastics
2 Thermo setting resins
These plastics have a medium modulus of elasticity and
the elongation under pressure completely disappears when i Casein
pressure is removed.
Casein is a phosphor protein and is derived by the
iii Soft plastics precipitation of milk with acids. If has bright attractive
appearance but not strong. It is used for buckles, buttons,
These plastics have a lam modulus of elasticity and the
etc.
elongation under pressure disappears sonly when the
pressure is removed. ii Melamine -formaldehyde
iv Elastomers It is obtained from calcium carbide, melamine when
reacted with formaldehyde, forms this resin. It possess
These plastics are of soft and elastic materials having
excellent resistance to electrical arcs. It is used for
low modulus of elasticity. The deformation is in tension
electrical insulators, glass reinforced plastics etc.
and the deformation disappears rapidly at room
temperature. iii Phenol formaldehyde
Resins Phenol is a carbolic acid it is extracted resin prepared
from this lightly resistant to heat. It possess both
The plastics are grouped in to two groups, based on their
mechanical and electrical properties. It is used for paints,
behaviour according to heating, resins or benders are also
varnishes, preparation of laminated products, electrical
broadly divided into the following groups.
fitting, w.c. seats etc.
1 Thermo plastic resins
iv Phenol farfuraldehyde
2 Thermo setting resins
Farfuraldehyde vapours when reacted with phenol, from
1 Thermo plastic resins resin. It is darie colour and resists very high temperature.
i Alkyd v Urea formaldehyde
These resins are made from glycerin and ophthalmic Urea is prepared from calcium cyanamide or a mixture of
anhydride. The cool slowly and possess electricity liquid carbon dioxide and liquid ammonia. Urea reacted
properties. They are used for preparing this felons of with formaldehyde produce this resin. It is not easily
plastics. attached by dilute acids and alkalies oil, chemicals, water
ii Celluloses etc. Plastics made from this resin are unidely* used for
making adhesives for wood, lighting fixtures, like lamps,
These are derived from various cellulose compounds like reflectors etc.
cellulose acetate, cellulose nitrate etc. Plastics made
from this are like glass. They are tough, strong and posses To give desired finished plastic articles, certain
electrical properties. Possible to obtain all types of moulding compounds are to added to plastics.
colours. Following are the such moulding compounds.

iii Coumarone - indene 1 Catalysts

These resins are soft in very small temperature. They 2 Fillers

are brittle and used for floor tiles, rubber manufacture etc. 3 Hardeners
iv Methyl methocrylate 4 Lubricants
This is known as acrylic. It is derived from coal petroleum 5 Pigments
and water. It transmits ultra-violet waves of light. It can be
6 Plasticizers
acts, sawn or turned it acts as good electrical insulator.
Plastics prepared from this are used for safety glass, 7 Solvents
artificial jewels, roof lights, lightening fittings, bath and
In plastic fabrication following are the process
sink units etc.
involved in the fabrication of plastic articles.
v Styrene
1 Blowing
This is the product form ethylene which is made from
2 Calendaring
petroleum . It is light an weight and transmits ultra- violet
waves of light. It possess very high electric resistance. It 3 Casting
is used as emulators at radio frequencies in wireless and
4 Laminating
television industry.
Construction - D’ man civil - R.Theory For Exercise 1.3.23 181
5 Moulding (compression moulding - extrusion moulding) 18 Weight : Plastics, whether thermoplastic or thermo
setting have low specific gravity, the a usage being
Properties of plastics
1.30 to 1.40. The light weight of plastic reduces the
1 Appearance : Some plastics are completing transport cost and easy to fixing .
transparent in appearance.
Uses of plastics
2 Chemical resistance :Plastics are great resistance
The typical uses of plastics in building are summarized
to moisture, chemicals and solvents. Many plastics
as follows.
are found to be corrosion resistance and hence they
are used to convey chemicals. 1 Bath and sack writs
3 Dimensional stability :This property of plastic is very 2 Cistern ball floats
satisfactory with that of other common engineering
3 Corrugated and plain sheets
materials.
4 Decorative laminated and mouldings
4 Ductility : It is lacks in ductility and may fail with out
warning. 5 Electrical conduits
5 Durability : Plastic and are quite durable. It possess 6 Films for water proofing, damp - proofing and concrete
sufficient surface hardness. curring
6 Electric insulation : Plastics are for superior to 7 Electrical insulators
ordinary electric insulators
8 Floor files
7 Finishing : Any surface treatment can be given to
9 Foams for thermal insulation
plastics. It is easy to have technical control during
manufacture. It results to man production with 10 Joint less flooring
uniformity of surface finish. 11 Lighting fixtures
8 Fire -resistance : Plastics are organic in nature and 12 Over heads water tanks
hence all plastics re combustible. Cellulose acetate
burns slowly. Polyvinyl chloride plastics are non - 13 Paints and varnishes
inflammable. Phenol formaldehyde and urea 14 Pipes to corry cold water
formaldehyde resist fire and they are used as fire -
proofing materials. 15 Roof lights

9 Fixing : Plastics can be fixed easily in position and 16 Safety glass

they can be bolted, clamps, drilled, glued, threaded 17 Wall tiles
simply push fitted in position.
18 Water resistant adhesives etc
10 Humidity : The properties of plastics are governed to
same extent by humidity, plastics which do not contain The advantages of PVC pipes
water attracting groups like polyvinyl chloride plastics 1 They have good insulating properties and hence the
offer great resistance to moisture. water passing through this is not affected by the out
11 Maintenance : It is easy to maintain plastic surfaces side temperature.
and they do not require any protective coat of paints. 2 The have no problems of incrustation .
12 Melting point : Most of plastics have low melting point 3 They permit high smooth and undionanished flam of
and some of plastics have 50°C. In general it can be water.
said that the co-efficient of thermal expansion of
plastics is ten times than that of steel. 4 They possess high Hazen Williams constant.

13 Optical property : Several types of plastics are 5 They prove to be economical as compared to other
transparent and translucent . pipe conventional materials.

14 Sound absorption : This material has absorption 6 They provide resistance to a variety of chemicals.
coefficient of about 0.67 Disadvantages of PVC pipes
15 Strength : Plastics are reasonably strong. Plastic 1 They are liable to creep phenomena, when installed
members can be used as tensile members. above ground level.
16 Thermal property : The thermal conductivity of 2 They can not be used in high temperature.
plastics is low and it can be compared with wood.
Foamed or expanded plastics are among the loading 3 They do not have same strength as cost iron or
thermal insulators. galvanized iron pipes.

17 Weather resistance : Only limited varieties of plastics 4 They possess higher co-efficient of expansion.
can be exposed to weather.

182 Construction - D’ man civil - R.Theory For Exercise 1.3.23

Precautions to be taken in the design and installation 8 They should not be used at places likely to be heavy
of PVC pipes. loading.
1 The design of PVC pipes should accommodate 9 The should not be bent too much.
adequate provisions of air vents etc.
• The properties of various types of plastics make them
2 The fittings such as tees, elbows, caps etc used in suitable for wide range of engineering applications. The
PVC piping system fit well with the pipes. development of plastic industry is very recent and have
much scope for research.
3 After installation the PVC pipes should be tested.
• Most of plastics possess low heat resistance
4 The turbulent flow of water through PVC pipes should
be avoided. • Plastics are not very low
5 The trances for laying PVC pipes should be as narrow • Plastics exhibits high creep
as possible.
• Plastics have high co-efficient of thermal expansion
6 They are available in different colours. It is advisable
• It varies from 25 x 10-6 to 120 x 10-6 as compared to 10
to avoid red and black colours.
x 10-6 of steel.
7 Should be used freely to eliminate external stresses

Construction - D’ man civil - R.Theory For Exercise 1.3.23 183

Construction
Draughtsman Civil - Foundation R. T. for Exercise 1.4.25

Site exploration
Objectives : At the end of this lesson, you shall be able to,
• define site exploration
• state the purposes of exploration
• explain preliminary investigation
• explain various method of site exploration

Introduction 3 The depth of rocks.

The knowledge of soil characteristics and the factors 4 Behavior of soils at site, which can be known from the
influencing their properties will help the investigation in type of construction and conditions of the structure
the identification of individual soils encountered in soils in the adjoining properties.
exploration and in the selection of right type of foundation
5 The general topographical features of site, viz, site on
for the building.
the top of hill, in a valley, on an abandoned lot, or
Definition: reclaimed ground etc.
For designing a right type of foundation safely and Methods of site exploration
economically, a designer must possess sufficient
1 Open excavation (test pits)
information about the physical properties and the
arrangement of the underlying materials. The field and 1 This method is useful when hard soil is available within
laboratory investigations required to get this essential a maximum depth of 1.5m
information are known as soil/site exploration. 2 A square pit, with side as about 1.50 m ,is excavated
General inspection of site up to a depth at which sufficiently hard soil is avaiable
It is desirable to visit the site of work and inspect the 3 A sufficient number of test pits should be dug on the
same carefully from the view point of foundation details. site to know the variation of the ground
The nature and thickness of strata of soil may be
estimated by studying the excavation details of near by
construciton or by examining the open side of a near by
well etc. The general inspection of site of work serves as
a guide for determine the type of foundation to be adopted
for the proposed work. It also helps in getting the following
data
Purposes
Before starting the exploration work, the following data
should be collected.
1 The nature, thickness and variation of soil strata in
the region.
2 Procuring representative samples for assessing the
Probing
physical properties of the soil strata encountered,
which in turn, will help in the design and mode of 1 Probing consists of driving either a hollow tube or a
construction of the proposed foundations. steel rod or an iron rod into the ground
3 The seasonal variation in ground water table and their 2 This method is possible to examine the ground for a
possible effects on the soil strata met. maximum depth of 3 m.
4 The strength and compressibility values of soil bed. Auger boring
5 If necessary, the depth of underlying rock bed. 1 An auger may be of post-hole type or screw type or
shell type
Preliminary Investigation
2 Auger is worked by applying leverage at the top the
The following information regarding the proposed site should
auger is driven into the ground and turned like a screw
be collected.
the auger is withdrawn and the material caught in the
1 The soil condition at different depths. slit is inspected.
2 Location of water table and its seasonal variations. 3 With the help of this method ,it is possible to inspect
the ground for a depth of 6 m to 8 m.
208
 4 Wash boring
The wash boring is the term used to denote a method in
which a casing is driven into the ground and the material
inside the casing is washed out and brought to the surface
for inspection.
5 Sub-Surface sounding
1 In this method, the resistance of the soil with depth is
measured by means of a tool known as penetro-meter
under static or dynamic loading.
2 This test is useful for :
i) Finding the depth of bed rock or stratum.
ii) Knowing the general exploration of erratic soil profiles
and
iii) Testing cohesion less soils from which it is difficult to
obtain the undisturbed samples.
6 Deep boring
1 It becomes essential to carry out deep boring for big
important engineering structures such as dams.
2 The machines used for deep boring are as follows.
i) Percussion boring machine.
ii) Core or rotary drilling machine.
7 Geophysical method
1 This method is used when the exploration depth is
substantial and the speed of investigation is of primary
importance.The method is mainly adopted to as certain
the depth at which useful minerals and oils are available.
2 The two most commonly adopted methods are as
follows.
i) Electrical resistivity method.
ii) Seismic refraction method.

Bearing capacity of soil

Objectives : At the end of this lesson, you shall be able to,
• define bearing capacity of soil
• explain safe bearing capacity of soil
• state ultimate bearing capacity of soil
• describe methods for determining the bearing capacity of soil
• explain methods of increasing bearing capacity of soil
• state the safe bearing capacity of various soil.

Introduction Ultimate Bearing capacity of soil

Bearing Capacity of soil is used to indicate the maximum The gross pressure intensity at which the soil fails.
load per unit area, which the soil will resist safely without
displacement, the load of the structure.
Safe Bearing capacity =
Safe Bearing capacity of soil
It is the maximum pressure, which the soil can carry The basic requirement of any structural components of a
safely. building is that it should be strong enough to carry or
support all possible type of loads
Construction - D’ man civil - R.Theory For Exercise 1.4.25 209
There are three types of load on the foundations Sl.No. Materials Weight in kg/m2
Design Loads 31 Lime mortar 1740
Dead load 32 Plaster cement 2080
Live load 33 Stone masonry 2500
Wind load 34 Asbestos cement sheet 12-15.60
Dead load 35 G.I Sheet(0.5mm thick) 5
This is the load of the material used for the various 36 G.I. Sheet(1.63mm) 13
components of a builidng such as wall floor roof etc. All
permanent loads are thus included in that load. 37 Mangalore tiles 68
Sometimes a dead load of 10kg/m2 of the floor area is Live load
allowed for construction of a partition wall.
This is the movable load on the floor and hence it is
The weight of common material are given below: variable. It is also sometimes known as super imposed
load. It includes load of person standing on a floor, weight
Sl.No. Materials Weight in kg/m2 of material temporarily stored on a floor, weight of snow
1 Aluminium 2590 on a roof etc. For the purpose of dressing the live load is
converted into equipement dead load. Super imposed load
2 Bitumen 1440 for floors of different types are as follows:
3 Coal tar 1000
Sl. Material Load kg/m2
4 Clay (dry) 1440
1 Residential building, hospital
5 Clay (damp) 1760 room and ward and hotel,
6 Earth (dry) 1410-1840 bed room etc 250

7 Earth (moist) 1600-2000 2 Office building, church,school

building, art gallories,stairs in
8 Sand 1540-1600 residential building retail shop
9 Sand(moist) 1760-2000 and light garages 400

10 Alcohol 780 3 Assembly building, public

building dance hall, theatre
11 Ice 910 restaurants, gymnasium,
12 Nitric Acid(91%) 1540 stair in public builidng light
workshop 500
13 Sulphuric Acid(87%) 1790
4 Heavy workshop,printing
14 Vegetable oil 930 press and factories 750
15 Water(fresh) 1000 5 Work houses, book stall,
16 Brick 1600-1920 sanitary stores and heavy
garages 1000
17 Cement(ordinary) 1440
18 Chalk 2240 Wind load

19 Glass 2400-2720 In case of tall building the effect of wind should be

considered. The exposed sides and roofs of such building
20 Lime stone 2400-2240 are subjected to wind pressure. And its affect is to reduce
21 Sand stone 2240-2400 the pressure on the foundation on the wind ward side
and to increase the pressure on the foundation on the
22 Steel 7850 lee-ward side.
23 Timber 650-720 The wind pressure will depend on the velocity of the
24 Brick masonry 1920 ground. The relation between wind pressure and wind is
generally expressed by the formula .
25 Plain concrete 2300
P = 0.007502
26 Reinforced concrete 2400
where p = wind pressure v = velocity of wind in km/hour
27 Cast iron 7200
Bearing capacity of soil
28 Copper 8590
A foundation should be designed to satisfy to essential
29 Lead 11360 conditions.
30 Marble 2700
210 Construction - D’ man civil - R.Theory For Exercise 1.4.25
i) It must have some specified safety againce ultimate Analytical Methods
failure.
Rankine's gives an analytical method for determining the
ii) The settlement under working load should not exceed ultimate bearing capacity is,
the allowable limits for the super structure.
The bearing capacity of soil is defined as the maximum 2
(1 + sinθ )
load per unit area which will resist safely without Qf = r0
2
displacement. (1 − sinθ )
The ultimate bearing capacity is defined as the maximum Where Qf = Ultimate bearing capacity
gross pressure at the base of the foundation at which the
soil mass fails in shear. Gross pressure is the total ro = density of soil at depth D
pressure at the base of the foundation, due to the weight q = The angle of internal friction of soil.
of the super structure, self weight of the foundation and
weight of earth fill if any. The safe bearing capacity may Method of loading
be defined as ultimate bearing capacity divided by factor
of safety.

Ultimate Bearing capacity

Safe bearing capacity = =
Factor of safety

Factor of safety means only a number to be selected

depends on how accurately soil conditions are known. Is
generally 2-3 for stable building.
MAXIMUM SAFE BEARING CAPACITY OF VARIOUS
SOIL

Sl Description M.S.B.C
No of soil in Tone/m
1 Very soft, wet, pasty or muddy clay 5
2 Black cotton soil in dry condition 15
3 Soft clay 10
4 Moist clay and sand clay mixture 15
5 Medium clay 25
6 Compact clay nearly dry 45
7 Fine sand, loose and dry 10
8 Medium sand compact and clay 25
9 Compacts and prevented from 45
spreading
10 Loose gravel 25
11 Compact gravel and moorum 45
12 Soft rock 45
13 Laminated rocks such as lime stone 165
This is a field test to determine the ultimate bearing
and sand stone
capacity of soil and the probable settlement under a given
14 Hard rock without defects such 330 loading. The test essentially consists in loading a rigid
as granite trap plate (usually of steel) at the foundation level.
Method for determining bearing capacity of soil Determine the settlement, corresponding to each load
The bearing capacity of soil can be determined by any increment. The ultimate bearing capacity is taken as
one of the following methods load at which the plate, start sinking at a rapid rate.

• Analytical method The ultimate bearing capacity in tone/m

• Method of loading
• Method of dropping a weight
Construction - D’ man civil - R.Theory For Exercise 1.4.25 211
Method of dropping a weight Compacting soil
In this method a substance of known -weight is dropped In this method the width of foundation is increased by
about 45cm or 50 and a layer of 30cm - 45cm of rubble is
Method of dropping a weight
spread over the bottom of the foundation as shown in (Fig
3). This layer of rubble is well rammed. If the material is
buried completely, another layer of depth about 15-25cm
is laid and it is well rammed. At the end of this process, if
the bearing capacity of soil is tested, it is found to have
increased considerably. This increasing bearing capacity
of soil may then be used for the design purpose.

In this method a substance of known -weight is dropped

from a known-height as shown in figure. The depth of
impression made by the weight on the soil is noted.
Then the bearing capacity of soil is worked out as follow:
If, R= resistance of soil
w= Weight of the substance
Drainage of soil
h= height
It is a well known fact that the presence of water decreases
d= depth of impression bearing power of soil. This is because of less shearing
Total energy = wh=Rxd strength of soil in presence of excess water. Drainage
results in decrease in voids ratios and improvement of
wh bearing power.
R=
d Confining the soil (sheet piling):-

ie, R= ultimate bearing capacity of soil The movement of soil under the action of load can be
prevented by confining the ground by use of sheet piles.
if A= Cross sectional area of the substance This will results in the increasing of bearing power of soil.
Grouting
R
= Resistance of soil per unit area. Bore holes in sufficient number are driven in the ground
A
the cement grout is then forced under pressure through
these bore holes. The cracks or fissures of the rocks are
R these filled up, resulting in the increase of bearing power
Bearing capacity =
A of soil.
Chemical Treatment
R
safe bearing capacity = In this treatment certain chemicals are used in place of
AxF cement grout to solidify the soil. But as this process is
costly it is adopted only in case of important building.
Where F= factor of safety.
CAUSES OF FAILURE OF FOUNDATION AND
The results obtained by this method are approximate and
MEASURES TO PREVENT SUCH FAILURE
hence this method is used for minor engineering structure.
The unequal settlement of sub soil may be due to
Method of improving bearing capacity
• Unequal distribution of load on foundation.
Increasing depth of foundation
• Varying bearing power of subsoil.
It has been found that in granular soil the bearing capacity
increase with the depth due to the confining weight of • Eccentricity of the load
overlying material. It is not economical since the cost of
construction increases with the increase in depth. This
method is useful when bearing straturm is met at greater
depth.

212 Construction - D’ man civil - R.Theory For Exercise 1.4.25

Due to unequal settlement of the subsoil, cracks are Horizontal movement of the earth
formed in the building. This failure can be prevented by
Very soft soil is liable to give away under the action of
• Foundation should be rest on rock or hard moorum. load, especially as places such as sloping ground, river
banks etc. Hence in such cases it is desirable to construct
• Proper design of the base of footing. So that it can be
retaining walls or to drive a sheet piles to prevent the
resist cracking.
escape of earth.
• Avoiding eccentric loading
Transpiration of trees and shurbs
Unequal settlement of masonry
The roots of trees planted near a building may extent
Mortar joint may shrink and compress which may lead upto the foundataion level and may absorb the moisture.
to unequal settlement of the masonry. This effect is seen in the form of a depression on the
This failure can be prevented ground, and it may lead to crack in the building. To
prevent such failure.
• Using mortar of proper strength.
• The foundation should be taken sufficiently deep at a
• Using thin mortar joint. minimum depth of 1m is required for this purpose.
• The height of wall to be raised per day should be limited • The trees should not be planted near the building with
to 1m in lime mortar and 1.5m in cement mortar. a distance of 8m.
• Properly watering the masonry. Atmospheric action
Withdrawal of moisture from the sub soil Rain and sun are the main atmospheric agents to
This occurs at places where there is considerable variation seriously effect the foundation of a building. Heavy rain
in the height of water table. When water table falls the or considerable variation in temperature or thrust action
soil particles loose cohesion and hence, there is shrinkage may damage the foundation. If the water remains stagnant
of soil, resulting in the cracks to the building. To prevent near the foundation it will remain constantly damp resulting
such failure,drive piles upto the hard rocks. in the decrease in strength of footing or foundation wall.
Hence it is always recommended to provide suitable wind
Lateral pressure on the super structure protection along the external wall by
The thrust on a pitched roof or arch action, or wind action • Filling back the foundation trenches with good soil and
on the super structure causes wall to overturn. compacting it.
To prevent such failure, provide a sufficient wide base and • Providing a gentle ground slope away from the wall.
to design the foundation for the worst condition.
• Suitable underground drains should be provided to
maintain water table at definite level.

Foundation
Objectives : At the end of this lesson, you shall be able to,
• define foundation
• state types of foundation
• explain purpose of foundation
• explain various loads on foundation
• describe causes of failure of foundation and its remedies.
Introduction Definition
Every structure consists of two parts, namely foundation The lowest artificially prepared part of the structure, usually
and super structure. Foundation is the lowest part of a located below the ground level, which transmit the load of
structure which transmits the weight of the structure, the superstructure to the ground is known as substructure
together with the effect of live loads and pressure, to the or foundation.
material on which the structure rests in such a manner
that the underlying material is not stressed beyond its
safe bearing capacity.

Construction - D’ man civil - R.Theory For Exercise 1.4.25 213

 Types of foundations

Foundation

shallow Deep foundation

Strip/wall Column Raft /Mat Grillage Inverted arch Stepped

Isolated Combined footing

Rectangular Trapezoidal Combined column-wall

square Circular Rectangular

Pile foundation Pier foundation Well/Caisson

Types of loads
1 Dead load 2 Live load 3 Wind load 4 Snow load
Causes of failure of foundations and its remedies
Causes Remedies
1 Unequal settlement of the subsoil Foundation should rest on rigid strata.
Design of foundations should be appropriate to the nature of
subsoil.
2 Unequal settlement of the masonry Using mortar of proper strength.
Masonry work should be raised evenly.
Proper Curing.
3 Withdrawal of moisture from the subsoil Provide drive piles up to the hard rock.
4 Lateral pressure on the superstructure Provide sufficient wide base.
5 Horizontal movement of the earth Construct retaining walls to prevent the escape of earth.
6 Transpiration of trees and shrubs Foundations should be sufficiently deep.
Trees should not be planted near the building.
7 Atmospheric action Provide suitable underground drains.
Providing gentle ground slope away from the wall.

214 Construction- D’ man civil - R.Theory For Exercise 1.4.25

Construction
Draughtsman Civil - Foundation R. T. for Exercise 1.4.26

Shallow foundation
Objectives : At the end of this lesson you shall be able to,
• define shallow foundation
• explain various types of shallow foundation
• describe setting out of building on ground.

Introduction Width of foundation

It is possible to construct foundation of a building at a The width of foundation should be sufficient enough to
reasonable shallow depth, the foundations are termed as bear the super imposed load per unit length on the
the shallow foundations. foundation bed. The width of foundation is obtained by
Definition i) Dividing the total load per unit length on foundation
The depth of foundation is equal or less than its width, is bed by safe bearing capacity of the soil.
known as shallow foundation.
w
Setting out of building on ground Thus, width of foundation =
p
1 Clear the Site.
Where, w = total load in tone/metre
2 Prepare a plan of setting out on paper.
p = safe bearing capacity of soil in tonne/m2
3 Centre lines of walls to be marked on plan
ii) Width of foundation = 2 (T+J) Where,
4 This is to be marked on ground.
T= thickness of wall above the plinth level.
5 Mark the centre lines of walls by stretching a string
between wooden pegs. J= the projection of concrete block on the either side of
the lowermost masonry footing. which should be atleast
6 Cross walls set by 3, 4,5 method.
10cm-15cm.
7 Corners of building are laid and sides checked by
Depth of foundation below ground level
measuring diagonals.
This is generally determined by the rankine's formula.
8 Entire width of foundation marked
Which gives the maximum depth.
9 For big projects reference pillars of brick may be
Depth of foundation below the ground level,
constructed.
Shallow foundation 2
p ⎡1 − sin θ ⎤
d=
w ⎢⎣1 − sin θ ⎥⎦
Foundation having its depth less than or equal is its width
are known as shallow foundation. Since such foundation
are constructed by open excavation.
Where p = total load on soil in kg/m2
Hence those foundation having its depth even greater than
w = wt of soil in kg/m3
its width but are constructed by way of open excavation
are also come under shallow foundation. θ = Angle of repose of the soil.
Design of shallow foundation In order that all the shallow foundation should be taken to
a minimum depth of 80cm below the natural ground level.
Following data are required before design of a foundation
Unless hard soil is available within 80cm.
a The total load to be transmitted by the wall or pier to
Angle of repose
the foundation bed.
Angle of repose is the angle 95 the loose soil will make
b The results of trial pit and the corresponding bearing
with the horizontal, if allowed to remain free in loose
capacity of each strata of soil.
condition. The angle of repose of the soil varies with the
The design of foundation required the three terms, type of earth.
a Width of foundation. Depth of concrete block
b Depth of foundation below ground level. The depth of concrete block below the masonry footing
c Depth of concrete block below the masonry rooting. is calculated by using the formula

215
 2
3PJ
d=
m

Where, P = the load on soil in kg/m2

J= The projection of concrete on either side of the
lowermost masonry footing which should be at least 10-
15cm.
m= modulus of rupture of concrete in kg/m
The depth of concrete block below the masonry footing is
also determined by the formula

5
d= T
6

Where T = thickness of wall above the plinth level. column which require greater spread. The base of the
TYPES OF SHALLOW FOUNDATION column is made of concrete.

A) Spread footing iii) Sloped footing

The total load of the structure is transmitted to the base Fig 3 shows the sloped footing made in concrete base of
of the structure is spread out to a large area by spread
footing.
a) Strip footing
Spread footing for a wall is known as strip footing.
b) Pad footing
The spread footing for a single column is known as pad
footing or isolated footing.
The spread footing may be of the following types
i) Single footing
Fig 1 shows the single footing for a column in which the
loaded area (bxb) of the column has been spread to the

non uniform thickness. Greater thickness at its bottom,

smaller thickness at the top.
iv) Wall footing without step
Fig 4 shows the stepped footing for a wall consisting of
concrete base without step.
v) Stepped footing for a wall
Fig 5 shows the masonry wall have stepped footing with
a concrete base.
vi) Grillage foundation
A grillage foundation is a special type of isolated footing.
Generally provided for heavily loaded steel stanchions or
column, specially in those location where bearing capacity
of soil is poor. The depth of foundation is limited from 1-
1.5m. The load of the column or stanchion is distributed
size (BxB) through a single spread. or spread to a very large area by means of layers of tiers
of joist, each tier being placed at right angle to the next
Stepped footing tier.
The Fig 2 shows the stepped footing for a heavily loaded Grillage foundation are of two types:-
216 Construction - D’ man civil - R.Theory For Exercise 1.4.26
 each tier are held in position by 20mm diameter pipe
separators (tie rod 20mm diameter) as shown in Fig 6..
The grillage beams are embedded in concrete. Generally,
the minimum clearance of 8cm is kept between the grillage
beams. So that the concrete can be easily poured
,properly compacted. However the distance between
the flanges should not exceed 30cm or 1 1/2 times the
flange width. So that the filled concrete acts monolithically
with the beams. It should prevent their corrosion. A
minimum concrete cover of 10cm is kept on the outerside

Steel grillage foundation

Timber grillage foundation.
Steel grillage foundation of the external beams as well as upper flanges of top tier.
Steel grillage foundation is constructed of steel beams, Timber grillage foundation (Fig 7)
structurally known as rolled steel joist (RSJ) provided in
two or more tiers. In case of double tier grillage (which is Temporary grillage foundation in the form of timber beams
commonly provided) the top tier of grillage beams is laid may be provided to timber columns, posts or walls etc.
at right angle to the Bottom tier. The joists or beams of They can be design for supporting light building. In water
Construction - D’ man civil - R.Theory For Exercise 1.4.26 217
logged areas. The loading on the soil is limited is 5.5 individual columns, connected by a beam called a strap.
tone/m. The grillage takes the form of a platform of wooden When a column is near or right next to a property limit,
planks arranged in 2 layers at rectangle to each other. its foundation cannot extended beyond the property line,
and if the distance between this columns and the adjoining
column is large, in that case strap footing may be provided.
The strap beam connecting the spread footings of the
two columns do not remain in contact with soil and does
not transfer any pressure to the soil. The function of
strap beam is to transfer the load of heavily loaded outer
column to the inner column. In doing so the strap beam
is subjected to bending moment and shear force and it

The two layers of planks are separated by rectangular

should be suitably designed to withstand these.

iii) Combined footing
RECTANGULAR FOOTING (Fig 9)
A spread footing which supports two columns is termed
has combined footing. If the footing supports more than
two columns it is known as continuous footing.
A combined footing is provided under the following
circumstances
1) When the columns are very near to each other so that
their footings overlap.
2) When the bearing capacity of soil is less requiring
more area under individual footing.
3) When the end column is near a property line so that
its footing spread in that direction.
A combined footing may be rectangular or trapezoidal in
plan. The aim is to get uniform pressure distribution under
the footing. For this the centre of gravity of the footing
area should coincide with centre of gravity of the combined
section of timber placed at centre to centre distance of load of two columns. If the outer column, near the properly
about 3.5cm-40cm.
B) Strap footing or cantilever footing (Fig 8)
A strap footing comprises of two or more footings of
218 Construction - D’ man civil - R.Theory For Exercise 1.4.26
line carries heavier load, provision of trapezoidal column
becomes essential to bring the c.g of the footing in line
with the c.g of the two column loads. In other cases
rectangular footing may be prefered.(Fig 10)
IV) Mat or raft foundation
Generally a raft or mat foundation is used when the bearing
capacity of soil is very poor and when it is required to
distribute heavy concentrated load over a large area. The
raft foundation is useful where there is a possibility of
unequal settlement to occur. The raft foundation consist
of thick R.C.C slab covering whole area in the form of a
mat. If the required area of footing exceeds half the total
area of the structures, raft foundation is used. Raft
foundation is also used for increasing the area of foundation
to neutralise the hydrostatic uplifts.
v) Inverted arch foundation - The foundation which
consist of inverted arches between the pier are known as
inverted arch foundation. The rise of the arch is about
1/5th -1/10th of the span. The load transmitted to the soil
through inverted arch. These are suitable for the
construction of bridges, reservoirs, tanks etc. Now a days
this type of foundation is rarely used in India.

Construction - D’ man civil - R.Theory For Exercise 1.4.26 219

Construction
Draughtsman Civil - Foundation R. T. for Exercise 1.4.27 to 1.4.29

Deep foundation
Objectives : At the end of this lesson, you shall be able to
• define deep foundation
• state classification of deep foundation
• explain pile foundation
• identifies various types of piles
• describe pier foundation
• explain well foundation (caisson).

Introduction Definition
This construction is adopted when the loose soil extends The depth of foundation is greater than its width is called
to a great depth. The load of the structure is transmitted deep foundation.
by the piles to hard stratum below or it is resisted by the
friction developed on the sides of piles.
Classification of deep Foundation

Pile foundation Pier Foundation Well Foundation (Caissons)

A Pile Foundation
Pile is a long vertical load transferring member which may
be of timber, steel or concrete.
1 The loads are taken to a low level by means of columns
in the soil.
2 It may be adopted where no firm bearing strata exists
at reasonable depth and the loading is uneven
3 The pumping of subsoil water is too costly for keeping
the foundation trench in dry condition.
Classification of piles
4 This foundation is to be adopted for the structures in
the area where canals ,deep drainage lines, etc. are (a) Classification according to foundation:-
to be constructed
1 End bearing piles (Fig 2)
Pile
Following are the situation in which a pile foundation is
preferred:-
a When the load coming from the structure is very high
and concentrated.
b When the other type of foundation cannot be provided
due to heavy cost and site difficulties.
c When the water table is very near to the ground level
and may defect the other type of foundation.
d When due to heavy inflow seepage, it is not possible
to execute the trenches and keep them dry.
e Where there are chances of construction of irrigation
canal in the near by area, which causes seepage of
water in the foundation.
Piles whose lower end rest on hard rock (hard stratum) is
f When hard bearing strata is at a greater depth.
known as end bearing piles. These piles are used to
transfer heavy load through water or soft soil to a suitable
hard stratum.
220
 Types of pile

Piles

Load bearing Pilles Non - Load bearing piles

Cast iron pile

Concrete sheet pile

Concrete pile

Sand pile
Steel sheet pile
Timber pile

Steel pile
Timber sheet pile
Wrought iron pile

Composite pile

Cast in situ concrete pile Pre cast concrete pile

Cased Cast in situ concrete pile Un cased cast in situ pile

Swage pile Simplexpile

Raymond pile Franki pile

Button bottom Vibro pile

Monotube pile Pedestal

Mac-Arthur pile Pressure

Cobi pneumatic

Button bottom

Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29 221

2 Friction piles (Fig 3) to uplifts due to hydrostatic pressure or due to
overturning moment.
The piles which support the structure load due to friction
between the piles and surrounding soil are known as 5 Anchor piles
friction piles. Such piles are generally use in granular soil
These piles provide anchorage against the horizontal pull
when the depth of hard strata is very great.
from sheet piling or other pulling force.
6 Sheet piles
The piles are differ from bearing pile and friction pile. In
that they are rarely used to furnish vertical supports, but
are used to retain the soil that is, liable to escape laterally
when subjected to pressure or to enclose the area required
for some foundation. And protect it from the action of
running water or leakage.
7 Fender piles and dolphins
These piles are used to protect the concrete deck or other
water front structures against impact from ship or other
floating objects.
8 Batter piles
These piles are driven at an inclination to resist large
horizontal or inclined forces.
b) Classification according to materials used
1) Concrete piles
2) Timber piles
3) Steel piles
4) Composite piles
3 Compaction piles (Fig 4) 1 Cement concrete piles (Fig 5)

Compaction piles are used to compact loose granular

soil thus increasing their bearing capacity. The
compaction piles themselves do not carry any load.
Hence they may be made of weaker materials like timber,
bamboo sticks etc. Sometimes they may be made of
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.
4 Tension or uplift pile
Cement concrete possess excellent compressive strength.
The tension piles anchor down the structures subjected R.C.C piles are becoming more popular and they are fast
222 Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29
replacing piles of other material. R.C.C piles are divided Advantages of cast-in-situ concrete piles
into two groups.
a Light weight shells are used in cast-in-situ concrete
i Pre cast concrete piles (Fig 5) piles and these shells are easy to handle and to
drive in the ground.
Pre-cast concrete piles are those which are manufactured
in a factory or at a place away from the construction site b No extra reinforcement is necessary to resist stresses
and then driven into the ground at the place required. They developing during handling or driving operation only.
may be square and octagonal piles are cast in horizontal
c There is no wastage of materials as the piles of required
form. The round piles are cast in vertical forms. The size
length is constructed.
of the piles may be 30cm-50cm and the length may be
much as 18m or moré. d The pile are sound in construction as they are not
driven into the ground by a hammer.
The reinforcement may consist of longitudinal steel bars
of 20-40 mm in diameter 4-8 No's with lateral ties of 5- Disadvantages
10mm wires spaced at 10cm-30cm c/c from bottom to a It is difficult to maintain the reinforcement in correct
middle respectively. A concrete cover of atleast 50mm is position during construction of piles.
provided as shown in figure. At the toe of the piles a steel
shoe is generally provided. The steel shoe protect the toe b These pile cannot be constructed under water.
and helps the pile in penetrating into the ground during c The dry ground may absorb, moisture from the wet
the driving. Pre-casting piles are useful in carrying fairly concrete. The piles are then weakened.
heavy loads through soft materials to tinner strata.
2 Timber piles (Fig 6)
Advantages of pre-cast concrete piles
a The position of reinforcement in pile is not disturbed
from its original position.
b These piles can be driven under water. Concrete in the
cast-in-site piles may not be set under water.
c It is possible to have a proper control over the
composition and design of these piles as they are
manufactured in a workshop.
d Any defect of casting such as hollows etc can be found
out and repaired before driving the pile.
e Any number of piles can be manufactured at a
convenient place and this may prove to be economical.
f These piles process high resistance to biological and
chemical action of the ground.
g These piles, when driven are ready to take up the load.
There is no wastage of time.
Disadvantages of pre-cast concrete piles The timber pile may be rectangular, circular, square. The
size of timber varies from 30cm-5-cm. The length of the
a These piles are heavy in weight and it is therefore timber pile does not exceed 20times its top width
difficult to transport, to handle and to drive them. otherwise it may fail by buckling. At the bottom a cast-
b Extra reinforcement is provided to resist the stresses iron shoe is provided and at the top, a steel plate is fixed.
during handling and driving operation. This fact makes The timber pile should be properly treated so as to make
the pile costly. them durable.
c If sufficient care is not taken, piles may break during A timber pile is made of trunk of a tree. The wood to be
transport or driving. used for timber pile should be free from knots. flaws and
shakes and other defects. The common Indian timber
d The size and length of pile will depend on the available which are used are babool, chir, jarul, poon,. Sal, teak.
transport facilities.
Advantages of timber piles
ii) Cast-in-situ concrete pile
a Where timber is available easily these piles prove to
In this type of concrete piles a bore hole is dug into the be economical in cost.
ground by inserting a casing. This bore is then filled with
concrete after placing reinforcement, if any. The casing b These piles can be handled easily with little risk or
may be kept in position or it may be withdrawn. The former danger of break.
piles are known as cased-cast-in-situ concrete piles and c The length of the timber pile can be adjusted either by
the latter is known as uncased-cast-in-situ concrete piles. cutting or lengthening without must extra cost.

Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29 223

d Skilled supervision is not required in the construction piles, tubes or pipes of steel are driven into the ground.
of timber lile. The pile may be driven either with open end or with closed
end. Concrete is filled in side the tube piles. Because of
e These piles can be removed easily if necessary.
circular cross section these piles are easily to handle
f These pile donot required heavy equipment for driving and easy to drive.
them into the ground.
Disadvantages
a These piles cannot be take heavy loads and are
unsuitable for used as end bearing piles.
b A joint in the lengthened timber pile is a source of
weakness.
c It becomes very difficult to drive these piles in the
hard formation.
d Timber piles are generally used for temporary work.
3 Steel piles
Steel piles are used as load bearing piles in the different
form.
i H-beam piles
ii Box-piles
iii Tube-piles
i H-beam piles
Fig 6 shows the plan of an H-beam steel piles. These
piles are usually of wide flange section and they are most
common variety of steel piles in general use. They are
found very much suitable especially for trested type
structure in which the pile extent above ground level and
work also as column for the structure. The driving of H-
piles is very simple and energy from a piles hammer is
effectively transmitted to the lower portion of the pile.

Advantages of steel piles

a These piles withstand easily the stresses due to
driving.
b These piles can be easily to lengthened by welding
without any delay in driving operation.
c The extra length of these piles can be cut off easily.
d The bearing capacity of these pile is comparatively
high. The allowable compressive stress on steel is
taken as about 6-8 kg/mm2
e These piles can be handled roughly without any serious
damage.
Disadvantages
ii) Box pile
a Corrosion is the only drawback of steel pile.
Fig 8 shows the plan of box pile. Various type of patended
box piles are available, the figure shows "Larssen-Box 4 Composite piles
pile". A box is driven either with closed bottom or with
Composite piles are those which are made of two portion
open bottom. These piles are used when it is not possible
of two different materials driven one above the other. Two
to drive H-beam piles upto the hard strata.
common type of composite piles are :
iii) Tube piles
a Timber and concrete pile
Fig 9 shows the plan of tube pile. In this type of steel
In the timber and concrete composite pile, timber portion
224 Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29
is use below the permanent or lowest water level, while masonry. In masonry well vertical holding down bolt and
concrete piles, usually cast-in-situ is formed above it. iron plate or loop iron are provided to secure good bond.
Due to this combination the advantages of both types are
combined. Also the total cost of the pile is reduced.
b Steel and concrete composite pile
This type of composite pile is used where the required
length of pile is greater than that available for the cast-in-
situ type pile. The pile consist of steel pile attached to
the lower end of concrete pile. This type of composite
pile is used where satisfactory penetration of the pile into
the rock is required for heavy loads.
Foundation for black cotton soil
Black cotton soil is a loose type of soil, and it considerably
swells and shrinks by variation in moisture content. The
variation in the volume of the soil is to the extent to the
extend of 20%-30% of the original volume. During rainy
season moisture penetrates into the soil the particles
separate out, resulting in increase in the volume.
This increase in volume is known as swelling. During
summer season, moisture moves out of the soil and
consequently the soil shrinks, shrinkage cracks are
formed on the ground surface. These shrinkage cracks
are formed on the ground surface. These shrinkage cracks In order to prevent cracks during sinking operation. At the
sometimes also known as tension cracks may 10-15cm bottom of the well curb made of concrete, a steel or cast
wide,1/2-2m deep. Hence extreme care should be taken iron, cutting edge is attached. The position of well to be
when foundation are to rest on this soil. sank is first correctly marked on the ground and the curb
is placed upon it. On the curb masonry ring is built to a
Following are the precautions to be taken in designing hight of about 1.2m and allowed to drying.
footings on black cotton soil:-
Type of foundation in black cotton soil
a For important structure the raft foundation should be
adopted. Foundation in black cotton soil may be of the following
types.
b The black cotton soil should be completely removed if
possible and convenient. 1 Strip or pad foundation

c The black cotton soil should not be allowed to come 2 Pier foundation
in direct contact with the foundation masonry. 3 Under-reamed pile foundation
d The construction work should be carried out in dry 1 Strip or pad foundation
season.
For medium loads strip foundation (for walls) and pad
e The depth of foundation should extend beyond the depth foundation (columns) may be provided. These are two
of crack in black cotton soil. method of strip or pad foundation.
Pile cap and pile shoe 1st method
When the column or any other load carrying structural This method of constructing foundation on black cotton
component is supported on more than one pile, the pile soil is adopted when the depth of black cotton soil is
should be connected through a rigid pile cap, to distribute more and there are not chances for surface water to
the load to individual pile, pile cap maintain the proper penetrate through the soil for more than 1m-1.5m.
alignment of the pile. It is advisable to ensure that a pile
projects atleast by about 10cm in the pile cap. The procedure is as follows

Pile shoes are provided at the tips to facilitate the process a The foundations trenches are excavated to a depth
of driving through hard strata. Pile shoes are made from given by the equation.
cast iron, steel or wrought iron. In case of steel piles it is d = maximum depth of crack+30cm
necessary.
b The width of the trenches is kept such that the allowable
B Well foundation(caissons) bearing capacity of the soil does not exceed 15 tone/
Well foundation is the convenient of securing a trust worthy m2.
foundation in deep sand or soft soil. It is also useful in c Gravel is spread for the face width of the trench and
moderate depth of water when foundation is to be taken well rammed.
in soft sandy soil, well are generally made of concrete or
Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29 225
d A layer of concrete of 50cm depth is laid on the gravel. e 80mm diameter pipes spread at 1.5cm centre to centre
are placed through the masonry and R.C.C slab, as
e The masonry work is started on the top of the
shown in figure. The pipes are brought upto plinth level
foundation soil and it is carried out upto the plinth level.
and filled with sand. A plug is provided at the plinth
f The side of the trenches are filled with sand as shown level. These piles are inspected periodically if required.
in fig 11.
2 Pier foundation (Fig 13)

II method
This method of constructing foundation on black cotton
soil is adopted at places where there is heavy rain-fall
and there are chances for surface water to reach a greater
depth in the soil.

When a heavy loaded building is situated in a sandy soil,

black cotton soil or soft soil, over lying hard bed at
reasonable depth pier foundation are sometimes used to
transfer the load the building to the hard bed below. This
method consist in sinking vertical shaft upto hard bed
and filling them with concrete.
The diameter of the shaft and the centre to centre spacing
depend upon the loading condition, the nature of soil and
depth at which hard bed is situated. The diameter or
horizontal dimension should be less than 1/12th its height.
To prevent the side earth from falling in the side, the shaft
is sometimes lined with timber. The timber lining is
removed during the filling upthe shaft with concrete. The
shaft are connected to each other by an arch or reinforced
cement concrete or steel grillage cap.
3 Under reamed pile foundation
The procedure as follows These piles are developed for serving as foundation for
black cotton soil. An under reamed pile is a bored concrete
a The foundation trenches are excavated to a depth of pile having one or more bulbs in its lower portion. The
2m. bulbs or under-reams are formed by under reaming tools.
b The side portion of the trenches are filled with concrete The foundation will be anchored to the ground, and it would
having a section of 25cmx25xm as shown in fig 11 not move with the movement of the soil. The diameter of a
and the hollow space equal to 1st layer of masonry is under-reamed pile is about 3m-8m. The spacing of pile
filled with sand. may vary from 2m-4m. The safe load for an under reamed
pile varies from 20 to 40 tone (Fig 14).
c 12cm-15cm thick R.C.C slab covering the face width
of the trench is laid. The load carrying capacity of under reamed pile can be
increased by adopting pile of large diameter or by
d The masonry work is started on the top of R.C.C slab extending the length of pile, or by making more bulb at
and it is carried upto the plinth level. the base. A single under-reamed pile has only one bulb at
226 Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29
the bottom. When the no.of bulbs at the base (2 or more) COFFER DAM AND CAISSON
it is known as multi under-reamed piles. The vertical
Coffer dam
distance of bulbs varies from 1.25 to 1.50 times the
diameter of the bulb. The under-reamed pile is selected Is defined as a temporary structure which is constructed
by the consideration of pile length, stem diameter, bulb so as to remove water and soil from an area and make it
diameter, a no of bulbs. In black cotton soil the bulb of possible to carry out the construction work under
under-reamed piles, not only increase the load bearing reasonably dry condition.
capacity, but also provide anchorage against uplifts. Following are the uses of coffer dam
1 To facilitate the pile driving operation
2 To place grillage and raft foundation.
3 To construct foundation for pier and abutment of bridge,
dams etc.
4 To provide working platform for the foundation of
buildings when water is met with.
5 To provide space for carrying out the foundation work
without disturbing or damaging the adjoining structure
such as building, pipe line etc.
Caisson
It is defined as a structure which is sunk through ground
or water to exclude the water and semifluid material during
the process of excavation of foundation and which
subsequently becomes an integral part of the sub-
structure.
Following are the use of the caisson
1 To reach the hard bearing stratum for transferring the
load coming on supports for bridge pier
2 To serve as an impervious core wall of earth dams.
when place adjacent to it.
3 To provide on acces to a deep shaft or tunnel.
4 To provide an encloser below water level for installing
machinery, pump etc.
The main difference between coffer dam and caisson
is that the coffer dam is a temporary structure, while
caisson forms the part of the permanent work.
Method of settingout of foundation trench
Setting out or ground tracing is the process of laying down
the excavation lines and centre lines etc on the ground.
The process for setting out of foundation trenches as
Stepped foundation on slopping ground
follows :-
1 When the ground is sloping it becomes an-economical
1 From the site plan of the building one line which can
to provides foundation at same level along the length
be easily established on the ground is selected.
of the wall, in such cases stepped or benching
foundation may be provided. The foundation trunch is For example as per fig16 the point 'A' can be easily
excavated in the form of steps, if possible all the steps located on the ground and its co-ordinates are
should be of equal depth and length. Overlap between completely defined. With the help of point 'A' line 'AB'
two layer of foundation concrete should be atleast can be demarcated on the ground.
equal to the depth of foundation concrete. A minimum Thus line 'AB' will be the base line and from this base
depth of 1m for soil and 60cm for rock should be line the entired building can be traced out on the ground.
provided between sloping surface and the lower edge It should be noted that the point 'A' and 'B' are on the
of the footing. centre line of the wall and hence it is essential to
prepare the centre line plan of the building before
starting this work.

Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29 227

2 Centre line wooden pegs are driven on the ground and 5 Along the centre line pegs brick pillars of size 20cm x
they project about 25mm above the ground level. Nails 20cm are constructed about 2m away from centre. In
are provided on the top of the pegs as shown in figure. some level upto plinth level height. The top surface of
the piller is plastered and grooves showing centre lines
3 Two other pegs are driven at equal distance on either
are provided as shown in figure.
side of the centre line peg such that the distance
between them becomes equal to the width of the 6 The masonry pillar should be preserved till the
foundation tranch as shown in figure 16. foundation work is completed.
4 With the help of these pegs the foundation plan can 7 The depth of excavation can be started.
be completely traced on the ground. For this purpose
8 The depth of excavation is check by fixing a strings
strings are tied to respective pegs and lines are marked
along the grooves on the opposite pillars and holding
along these strings with the help of pick-axe or wing
boning rod. The length of the boning rod should be
powder.
equal to the depth of foundation trenches.

228 Construction - D’ man civil - R.Theory For Exercise 1.4.27 to 1.4. 29

Construction
Draughtsman Civil - Foundation R. T. for Exercise 1.4.30

Simple- Machine foundation

Objectives: At the end of this lesson you shall be able to
• state the functions of a foundation bolt
• name the type of foundation bolts
• explain the specific application of the bolts.

Machines are generally subjected to the vibration of

forces. Due to this cause the machines are like to shift or
move or dislocate from their positions. To over come this
defaults the machines are fixed to the ground with the
help of specific devices which are called as foundation
bolts.
These bolts do not have a specific shape of head similar
to hexagonal or square bolts. The length of the shank is
according to the thickness of nut and the thickness of
machine base. The odd shaped part of the bolt hold the
machine firmly to the ground and preventing the machine,
shift or move or dislocation from its positions.
Types (Fig 1 & 2)

As per IS : 5624-1971 there core six types designated as

type A, B, C, D, E & F figure 1 shows the same. These
bolts are available in 13 dia sizes from M8 to M75, length
80mm to 320mm. These botls are designated by the
shanks dia and length without nut . The ends tare formed
by forging .
There are other non standard forms which are generally
used are
• Eye foundation bolt
• Rag foundation bolt
• Lewis foundation bolt
The position of the holes of machine base /feet marked
on the ground. Pits are formed and foundation bolts are
placed in position, with cross bars placed in bolt eyes.
The position of eye bolt is checked and aligned. The thread
and of the bolt protrude above the ground level. Cement
eye foundation bolt (Fig 2) and rubble are mixed with water
and pounced around the bolt. When it sets, the bolts are
hold in aligned. After this, the machine is placed in position
and nut are toughened on the bolts holding the machine
firmly.
Rag bolt (Fig 3)
This is in the shape of a rectangular pyramid with round
shanks are formed with rags or grooved, forming small
projections. These are bolts are placed in the foundation
cavity in position as done in previous case and then molten
lead of sulphur is pound around with. When the molten
lead or sulphur /lead solidified the bolts are held firmly.
The machines are placed in position and nuts are fixed.

229
By melting the lead or during the sulphur the bolt can be
removed.

Lewis foundation bolt (Fig 4)

This is a rectangular shanks bolt with one side taper.
AGIB headed key is placed on the other side of the taper
and concrete is panned around it if is aligned. The
foundation bolt can easily be with drawn by removing the
gib headed key first and then the bolt.
Cotter foundation bolt (Fig 5)
This type of bolt has a rectangular slot through which a
double headed cotter is placed. A cast iron washer is
rests above the cotter. Through the hand hole, connecting
the cavity in the concrete and the bolt is pulled down and
lifting the cotter. Now the cotter is placed in position.

230 Construction - D’ man civil - R.Theory For Exercise 1.4.30

Construction
Draughtsman Civil - Treatment for Building R. T. for Exercise 1.6.35

Damp proofing
Objectives : At the end of this lesson you shall be able to,
• define damp proofing
• state the causes and effects of dampness
• describe the requirements of ideal damp proofing material
• state the materials used for damp proofing
• explain the methods of damp proofing
• explain the water proofing treatments for roofs.

Introduction Effects of dampness

Dampness, is the unwanted and unauthorized 1 Metals used in the building corroded.
accumulation of water in the building components.
2 Unsighty patches formed
Continued presence of dampness in the building,
deteriorates building components, spoils, the interior 3 Decay of timber
decoration and external appearance and affects the health 4 Electrical deteriorated leakage of electricity and short
and comfort of the occupants. Hence, in order to prevent circuiting.
the entry of damp into a building, the application of courses
known as damp proofing courses, which are provided at 5 Floor covering materials get damaged
various levels, at entry of damp into a building. 6 Promotes the growth of termites.
Definition 7 Softening and crumbling of plaster
Treatments given to various places of building structure 8 Gives rise to breading of mosquitoes, germs of
to keep walls, floors and basement dry, is called damp dangerous diseases etc.
proofing.
9 Wall decoration materials are damaged
Causes of dampness (Fig 1)
10 Floorings get loosened
11 Cause efflorescence.
Requirements of an ideal damp proofing material
1 Durable
2 Remains steady and do not allow any movement it
self.
3 Perfectly impervious
4 Capable of resisting the loads coming over it safely.
5 Flexible
6 Dimensionally stable
7 Reasonably cheap
8 Possible to carryout leak proof jointing work
9 Free from deliquescent salts like sulphates, chlorides
1 Rising moisture from ground and nitrates.
2 Condensation Materials for damp proofing
3 Defective junctions between roof slab and parapet wall. 1 Bitumen
4 Defective roof covering of pitched roof 2 Mastic asphalt
5 Faulty eaves and valley gutter. 3 Bituminous felt
6 Improper rain water pipe connections 4 Metal sheets (Lead, Copper, Aluminium)
7 Inadequate roof slope 5 Combination of sheets and felts
8 Splashing of rain water 6 Stones
9 Unprotected tops of wall, parapet walls etc. 7 Bricks
241
8 Mortar 10 Plastic sheet.
9 Cement concrete
Methods of damp proofing
S.No Method Description / Figure
1 Integral treatment Water proofing compounds or materials are added during the process of mixing
the materials.

Chalk, tale or filler's earth is used to fill the pores in concrete or mortar.

Water proofing compounds such as Pudlo, Impermo etc. are used after diluting with
water.

Concrete is made water repellent by the use of soap solution, calcium and petroleum
oil etc.

2 Surface treatment Joints in brickwork or stone work are pointed or the surface is plastered.

Paints, oils, waxes and soap solution are used for surface treatment.

The cement paints act as vertical DPC.

3 Membrane damp This is done by providing a layer of water repellent materials between the
proofing source of dampness and part of the structure adjacent to it.

a (i) Treatment to
external walls

(ii) Treatment to internal

walls

242 Construction - D’ man civil - R.Theory For Exercise 1.6.35

S.No Method Description Figure

b Treatment to foundations
against gravitational water

c Treatment to basements

d Treatment to sloping
ground

e Treatment In pitched 1 In pitched roofs , the rain water gutters may be constructed in
cement concrete and standard rain water fittings may be used.

2 The gutters lined with bituminous

materials.

4 Cavitywall Cavity in
construction between two
walls prevents
the moisture from
reaching the
inner wall Cavity
wall prevent the
entry of dampness
Construction - D’ man civil - R.Theory For Exercise 1.6.35 243
 S.No Method Description Figure

5 Treatment to The expansion

expansion and joints and
construction joints construction
joints should
be properly
sealed by water
proofing
materials to
obstruct the
leakage of water.

6 Guniting Cement mortar consists of 1:3 is shot on the cleaned surface with the help
of a cement gun, under a pressure of 2 to 3 kg/m2.
Can be used over pipes, cisterns etc. for resisting water pressure
7 Pressure grouting Forcing cement grout, under pressure into cracks,voids,fissures etc.
present in the structural components of the building or in the ground

Water proofing treatment to flat roof 3 Then a layer of fine sand is spread immediately, when
the bitumen is still hot.
Flat roof must have to be provided with proper water
proofing courses. Leakage of water through roof occur 4 Over this 10 cm thick lime concrete is spread and
mainly due to stagnation of water at low area. To avoid rammed with light rollers to get even thickness or the
this roof must have proper slope towards the outlets. required slope.
Following are the commonly adopted methods of water 5 Ramming is continued till 10 cm laid thickness will
proofing treatments. come down to 8 cm.
A Cement mortar plastering 6 When lime concrete layer is still green, two courses
of flat brick tiles are laid in cement mortar 1:3.
1 The entire area of roof is cleaned with wire brush and
all dirt is removed. E Mud pushka terracing with tile paving
2 A neat cement wash is given to the surface and 1 At first a layer of hot bitumen is spread over the entire
roof surface.
3 20mm thick layer of cement mortar mixed with standard
water proofing compound is laid and finished smooth. 2 The prepared mud pakka earth is spread to a thickness
of 10 cm. and compacted to till the thickness reaches
B Tar felting
to 8cm.
Hot bitumen is applied over the roof surface and tar felt is
3 Over this 25mm thick layer of mud mortar is laid and
laid over it.
allowed to dry.
C Lime concrete terracing
4 After drying up, a coat of gobi leaping is given.
1 It is most common in southern region of India.
5 Over this a layer of flat brick tiles is laid in mud mortar,
2 They offer good resistance to solar radiation. and allowed to dry.
3 Lime concrete is made by mixing over burnt brick 6 Joints are pointed with cement mortar 1:3.
aggregate of size 25mm with lime mortar of 1:2mix.
7 Entire roof surface is covered with wet gunny bags.
4 First 10 cm thick lime concrete is laid, spread and
8 After 12 hours brick terracing is cured by sprinkling of
rammed with wooden rammers.
water.
5 Slope if required should be given in this layer.
Water proofing treatment for pitched roof
6 Then entire surface is consolidated by beating.
Usually the pitched roof has self draining property. The
D Lime concrete terracing with tiles over laps should be as specified and size of gutters should
1 As explained above, proportion, method of laying, be designed taking into consideration the average rainfall.
consolidation etc. is same. The common methods adopted for water proofing are:

2 At first a hot bitumen wash is given to the entire roof a Covering the entire roof surface with tar felt
surface. b Covering the entire roof surface by lime mortar of
proportion 1:1:2 (lime putty: surkhi: coarse sand)

244 Construction - D’ man civil - R.Theory For Exercise 1.6.35

Plastering
Objectives : At the end of this lesson you shall be able to,
• to improve the appearace of the structure
• to give smooth surface
• to protect from atmosphere
• to cpm ceal the inferior materials and defective workmanship
• to protect from termites.

Plastering • Rough cast finish

The method of applying mortar on the surface of masonry • Depeter finish
to protect the surface from atmospheric and to increase
• Scrapped finish
the beauty of the structure.
• Textured finish
Requirements of good plaster
Fibrous plaster boards
• it should adhere to the back ground
It is combination of plaster canvas and lath united into
• it should hard and durable
structural mass in the form of pre-cast slabs or moulding.
• it should possess good workability The fibrous plaster boards are available in different trade
names in the market. These boards are used as final
• it should be cheap and economical
finishes to the surfaces.
• it should be possible to apply in all weather conditions
Painting, Varnishing and Distempering
Types of mortar for plaster
According to the nature of the surface and finishing
• lime mortar required the surface are coated with paint, varnish,
• cement mortar distemper or colour wash, etc. Painting is applied over
surface of timber, metal or plasters, varnishing is applied
• lime cement mortar over wooden surfaces and painted surfaces. Distempers
• water proof mortar are applied over plastered surfaces and white wash applied
over distempered surfaces.
Method of plastering
Special material for plastered surface
• The mortar joints are raked to 20mm cleaned and well
watered. Material Uses

• A preliminary coat is applied to fill up the hollows Acoustic plaster To make the room sound
proof
• Dots of 9mm to 10 mm thick are formed to make
screeds at 2mm interval Asbestos cement Beautiful marble like finish
plaster
• The first coat of plaster is applied, 9mm to 10mm
thick Barium plaster Used in X-ray rooms to
protect the persons working
• The second coat of plaster is applied after about 6
hours with 2mm to 3mm thick Granite silicon plaster Quick setting highly elastic
and used for superior work
• If it is required a third coat also can be applied
Gypsum plaster Fire resisting light in
• The completed work is allowed to rest for 24 hours weight, not affected by
and well watered for at least one week. bacteria, used for
External finishes ornamental plaster, can be
applied with ease and less
Various types of external finished are given to the plastered wastage
surface to improve the appearance of the surface are
Keene’s cement Used for skirting work,
• Sand faced finish angles which gives glass
• Pebble dash finish like polish
Martin’s cement Internal finishing work

Construction - D’ man civil - R.Theory For Exercise 1.6.35 245

Painting
Objectives : At the end of this lesson you shall be able to,
• protect surface from weathering effects
• prevent decay of timber and corrosion in metal
• gives good appearance to the surface
• provides smooth surface for easy cleaning.

Methods of painting • Cleaning of surfaces removal rust, oil greease etc

• By brushes • Treatment with phosphoric acid protects rusting
• By spraying pistol • Priming coat
• By powder coating • Under coating
Method of painting on different surfaces • Finishing coating
Wood surfaces (new and repainting) Repainting old iron/steel
New woodwork • Cleaning with soap water
• Preparation of surfaces • Removal of old paint by flaming cleaning
• Knotting- Covering or killing of all knots in wood • Cleaning with caustic soda/slaked lime
surfaces by red lead with glue or shellac with spirit or
• Priming coat
lime.
• Under coating
• Application of priming coat.
• Finishing coat
• Stopping - rubbing down of priming coat by pumice
stone or glass paper or both Galvanized iron
• Under coating second coat and successive coats are • To adhere paint, treatment with copper acetate or with
applied another solution
• Finishing • After 12 hours of this primer coat is applied
Reprinting on old wood work • Under coating
• Removal of old paint • Finsihing coat
- With caustic soda Plastered Surfaces
- Mixture of soap, potash and quick lime Noted points are
- Washing soda and quick lime Paint recommened for plastered surfces are cement paint,
emulsion paint oil paint silicate paint etc
• Cleaning of surfaces
Surface is allowed to dry for 3 to 6 month to receive paint
• Under coating
Alkali resistant primer should be applied
• Finishing coat
Defects in plaster efflorescence should be removed
Metal surfaces
If necessary an antiseptic wash should be applied
New iron and steel surfaces
Under coat and finishing coats are applied
Defects in Painting
Defects Explanation
Blistering Formation of bubbles on painted surfaces due to water vapour
Bloom Formation of dull patches- due to bad ventilation
Fading Gradual of colour - effect of sunlight
Flaking Loose small portion - due to poor adhesion
Flashing Glossy patches seen - bad workmanship, cheap paint
Grinning Back ground is clearly seen - due to insufficient opacity
Running Paint run back leave small area - due to too smooth
Sagging When vertical and inclined surfaces are too thickly painted sagging occurs
Saponification Formation of soap patches

246 Construction - D’ man civil - R.Theory For Exercise 1.6.35

Varnishing
Objectives : At the end of this lesson you shall be able to,
• to brighten the appearance of natural grains in wood
• to render brilliancy to the painted surface
• to protect surface from atmospheric action.

Application of varnish on wooden or painted surface is Stopping

varnishing.
Stopping is done by means of hot weak glue size so that
Process of Varnishing the pores on the surfaces are filled up with boiled linseed
Preparation of surface oil.

The surface is smoothened by throughly rubbing it by Coats of varnishing

sand paper or pumice stone. On the cleaned surface, two or more coats of varnish are
Knotting applied .

The process of covering or killing all knots in the wood

work.

Distempering
Objective : At the end of this lesson you shall be able to,
• to create a smooth surface

Application of distemper on plastered surface is known Application

as distempering.
The white wash is applied with jute brush. Three coats
Process generally applied. Interior wall surface and ceilings are
white washed.
Preparation on surface : Surface is thoroughly rubbed and
cleaned. Colouring washing
Priming coat : It is applied and allowed to dry. Colour wash is applied in the same fashion as white wash.
This is prepared by adding the coloring pigment to the
Coats of distemper : First coat is applied with a light tint
screened white wash. Exterior walls and interior walls
and second coat is applied after heardening the first coat
are colour washed.
White washing
Preparation of surface : The surface to be treated is well
cleaned. The old loose white wash is removed and repairing
plaster is carried out.

Construction - D’ man civil - R.Theory For Exercise 1.6.35 247

Construction
Draughtsman Civil - Treatment for Building R. T. for Exercise 1.6.36

Termite proofing
Objectives: At the end of this lesson you shall be able to
• define the term termite proofing
• state the types of termites
• explain the methods of anti termite treatment.

Introduction Four litres of the above emulsion in water is required per

The removal of termites from a building is not an easy cubic metre of volume of mound.
task. The termites live in a colony and they are very fast b) Soil treatment
in eating wood and other cellulosic materials as food.
They damage materials of organic origin with cellulosic The best method to protect the building to protect against
base, damage house hold articles like furniture, termites is to apply a chemical treatment to the soil at
furnishings, clothing and stationary. Therefore it is the time of construction of the building. A complete
necessary to adopt anti termite treatment in building. chemical barrier is created.An insecticide solution consist
of any one of the following chemicals in water solution.
Definition
Chemical Concentration by weight
The treatment which is given to a building to prevent or
control the growth of termites is called termite proofing. Aldrin 0.5%

Types of termites Heptachlor 0.5%

Dry wood termites (Non sub Chlordane 1%

terranean termites/wood
nesting termites) The emulsion should be applied evenly at the following
stages.
Termites
Stage1-In foundation pits, to treat the bottom and sides
upto a height of 30 cm.

Subterranean termites / Stage 2-Refill earth on both sides of the wall, for a width
Ground nesting termites of 30cm and depth of 45cm approximately.

Methods of Anti-termite treatment Stage 3-Before laying the floor ,entire levelled surface is
1 Preconstruction treatment to be treated at the rate of 5 litres of emulsion per square
metre.
Here three operations involved.
a) Site preparation :- Remove stumps, roots, logs, waste c) Structural Barriers:- These are concrete layer of 5cm-
wood etc. Detect termite mounds and destruct these by 7.5cm thick or Metal sheets (Copper or G.I Sheets 0.8mm
using insecticide solution. Chemicals for preparing thick)
solution are DDT, BHC, Aldrin, Heptachlor, Chlordane.
Post construction treatment
Chemical Concentration by weight
It is a maintenance treatment. Open earth around building
DDT 5% and treat it with chemicals. In wood work or masonry
BHC 0.5% work, bore holes and inject chemicals.

Aldrin 0.25%
Heptachlor 0.25%
Chlordane 0.5%

248
Construction
Draughtsman Civil - Treatment for Building R. T. for Exercise 1.6.37

Fire protection
Objectives : At the end of this lesson you shall be able to,
• define the term fire protection
• state the important considerations in fire protection
• explain the fire resistant construction.

Introduction classes, namely type 1, type 2, type 3 and type 4 on

the basis of fire-resistance offered by building
Every building contains some materials which can either
components for 4-hours, 3- hours, 2-hours and 1-hour
easily catch fire or which are impossible to fire..However,
respectively. To achieve the objective of fire-resistance,
the architects and engineers should plan, design and
due considerations should be made in design and
construct the building in such a way that safety of the
construction of the structural members and use of
occupants may be ensured to the maximum possible
combustible material should be avoided as far as
extent.
possible in the construction
Definition
a) Walls and columns
It is defined as the protection of the occupants of the
b) Floor and roofs
building, contents and structure of the building and
adjacent buildings from the risks of fire and spread of fire. c) Wall openings
Important considerations in fire protection: d) Building fire escape elements (i.e.,) stair, staircase,
corridors, entrances etc.
1 It should be the objective of every engineer and arch
tect while planning and designing the building that the A Walls and columns:
structure offer sufficient resistance against fire so as
1 The load-bearing non-load bearing walls should be
to afford protection to the occupants, use of fire-
plastered with fire resistive mortar.
resisting materials and construction techniques and
providing quick and safe means of escape in the 2 Normally 20cm thick common wall is sufficient from
building. fire resistance point of view.
2 All the structural elements such as floors, walls, 3 Bricks should be preferred to stones if the construction
columns, beams etc should be made of fire resisting is solid bearing wall.
materials 4 For framed structures R.C.C. frames are preferred to
3 The construction of structural elements such as walls, those of steel frame.
floors, columns, lintels, arches etc 5 Partition walls, should also be fire resistant materials.
should be made in such a way that they should 6 Wooden partitions should be covered with metal lath
continue to function atleast for the time, which may and plaster.
be sufficient for occupants to escape safely in times
of fire. 7 Sufficient cover to R.C.C. members like beams or
columns should be provided.
4 The building should be so planned or oriented that the
elements of construction or building components can 8 It has been recommended that a cover of atleast 5cm
with stand fire for a given time depending upon the inside the main reinforcement of structural members,
size and use of building, to isolate various like columns, girders, trusses etc, 38mm for ordinary
compartments so as to minimize the spread of fire beam, long span slabs, arches etc, 25mm for partition
suitable separation is necessary to prevent fire, gases, walls, short spans should be provided.
and smoke from spreading rapidly through corridors, 9 Fire proofing treatments, which can possibly to
staircases ,shafts etc. concrete and steel column construction.
5 Adequate means of escape are provided for occupants B) Floors and roofs
to leave the building quickly and safely in terms of out
break of fire. 1 The floors and roofs should be made of fire-resisting
material as they act as horizontal barriers to spread
6 In multi-storeyed office buildings suitable equipment of heat and fire in vertical direction.
for detecting, extinguishing and warning of fire should
be installed in the niches. 2 The floor such as concrete jack arch floor with steel
joists embedded in concrete or hollow tiled ribbed floor,
Fire-resistant construction R.C.C. floor etc should be used as shown in figure.
National building code classifies the construction into four

249
C) Wall openings 2 Doors to the staircase, corridors and lifts should be
made of fireproofing materials.
1 The openings in the walls should be restricted to a
minimum and they should be protected by suitable 3 Staircase should be created next to the outerwalls and
arrangements in case of fire. should be accessible from any floor in the direction of
flow towards the exits from the building.
2 Wireglass panels are preferred for windows.
General measures of fire safety in building
3 Steel rolling shutters are becoming popular for door
ways and window openings in garages, godowns, In important buildings, in addition to the fire-resisting
shops etc due to their ability in preventing the spread materials and adopting fire resistant construction, the
of fire following general measures of fire-safety have been
recommended
D) Building fire escape element
i) Alarm system
1 Staircases, corridors, Lobbies, entrances etc are the
fire escape elements should be constructed out of fire- ii) Fire extinguishing arrangements
resistant materials and be well separated from the rest
iii) Escape routes for public buildings
of the building.
Thermal insulation
Objectives : At the end of this lesson you shall be able to,
• define thermal insulation
• state the advantages of thermal insulation
• state the thermal insulating materials
• explain the general methods of thermal insulation
• explain thermal insulation of roofs
• explain thermal insulation of exposed walls
• explain thermal insulation of exposed doors and windows.

Introduction General methods of thermal insulation

When there is difference in temperature of inside of a 1 Heat insulation by orientation

building and outside atmosphere heat transfer takes place • Orient the building with respect to the sun.
from areas of higher temperature to those of lower
temperature. The aim of thermal insulation is to minimize • During the day in summer minimum transfer of heat is
the transfer of heat between outside and inside of the desired.
building. • During winter maximum heating of rooms by solar heat
Definition is required.

The term thermal insulation is used to indicate the 2 Heat insulation by shading
construction or provision by way of which transmission • Shading of roof brings down the surface temperature.
of heat from or in the room is retarded.
• When the altitude angle of the sun is quite high ,during
Advantages the period of peak heat gain this method is not effective.
1 Comfort-Thermal insulation keeps the room cool in • Raising the parapet walls can help only when the
summer and hot in winter. altitude angle of the sun is low.
2 Fuel saving-Since heat transfer is minimized due to 3 Heat insulation by proper height of ceiling
thermal insulation,less fuel is required to maintain the
desired temperature in the room. • Provide a height of ceiling about 1 to 1.3 m above the
occupants.
3 Prevention of condensation-Use of thermal insulating
materials inside a room results in prevention of Thermal insulation of roofs
condensation(moisture deposition) on interior walls and Heat gain through roofs may be reduced by adopting the
ceiling. following methods.
Thermal insulating materials 1 Heat insulating materials may be applied externally
1 slab or block insulation. or internally to the roofs.

2 blanket insulation. 2 For flat roofs,external insulation may also be done by

arranging asbestos cement sheets or corrugated
3 loose fill insulation. galvenised iron sheets on bricks.
4 bat insulating materials. 3 Shining and reflecting materials may be fixed on the
5 Insulating boards. top of the roof.

250 Construction - D’ man civil - R.Theory For Exercise 1.6.37

4 Roofs may be flooded with water in the form of sprays 4 Heat insulating material may be fixed on the inside or
or otherwise. outside of the exposed wall.
5 Roofs may be white washed before on set of each 5 Light coloured white wash or distember may be applied
summer on the exposed side of the wall.
Thermal insulation of exposed walls Thermal insulation of exposed doors and windows
Heat insulation of the exposed walls may be achieved by Suitable methods should be adopted to reduce incidence
the following ways of solar heat and heat transmission.
1 The thickness of the wall may be increased. a) Reduction of incidence of solar heat:-This may be
achieved by
2 Cavity wall construction may be adopted, for external
walls. 1 External shading such as louvered shutters, sun
breakers, etc.
3 The wall may be constructed out of suitable heat
insulating material. 2 Internal shading such as curtains and venetian blinds.
b) Reduction of heat transmission-This can be
achieved by providing insulating glass or double glass
with air space.

Construction - D’ man civil - R.Theory For Exercise 1.6.37 251

Construction
Draughtsman Civil - Arches and Lintels R. T. for Exercise 1.7.38

Arches
Objectives : At the end of this lesson you shall be able to,
• define arch
• state the technical terms regarding the arch
• identify the components of arch
• classify the arches.

Introduction Intrados : Inner curve of an arch.

It is a geometrical shaped structure placed over an opening Soffit : Inner surface of an arch.
to transfer the load coming over it. It generally consist of
small wedge shaped units which are joined together with Extrados : Outer curve of an arch
mortar. Voussoirs : Wedge shaped units of masonry
Arches made of steel and R.C.C is built in single units Crown : Highest part of extrados
without the use of wedge shaped units and they are used
for bridge construction. Key : Wedge shaped unit fixed at the highest point of
arch.
Definition
Spandril : Curved triangular space formed between
An arch is a structure which is constructed to span across extrados and the horizontal line through the crown.
an opening.
Skew back : Inclined splayed surface on the abutment
Components of arch which is Prepared to receive the arch.
Springing point : Points from which the curve of the
arch springs.
Springing line : It is an imaginary line joining the springing
points.
Springers : The lowest voussoir immediately adjacent to
the skewback.
Abutment : End support of an arch
Pier : An intermediate support of an arch
Arcade : Row of arches.
Haunch : Lower half of the arch.
Span : Clear horizontal distance between supports
Rise : Clear vertical distance between highest point on
the intrados and the springing line.
Depth : Perpendicular distance between the intrados and
extrados.
Thickness : Horizontal distance measured perpendicular
to the front and back faces.

252
 Classification of arches
Arches

According According to According to According to

to shape number of centers materials used workmanship

1. Flat arch 1. One centered arch 1. Brick arch 1. Rough arch

2. Segmental arch 2. Two centered arch 2. Stone arch 2. Rough cut
3. Semi-circular arch 3. Three centered arch 3. Concrete arch 3. Gauged arch
4. Bull's eye arch 4. Four centered arch 4. Purpose made
5. Semi elliptical arch 5. Five centered arches
6. Inverted arch
7. Pointed arch
8. Relieving arch
9. Horse-shoe arch
10.Stilted arch
11.Venetian arch
12.Florentine arch
13.Ogee arch
14.Tudor arch
15.Drop arch.
Arches according to shape
Objectives : At the end of this lesson you shall be able to,
• classify arches according to shape
• state the technical terms regarding the arch
• classify the arches.

According to shape ,the arches are classified as follows. Classification of arches according to shapes
Classification of arches according to shapes
Name of arch Features Figure
1 Flat arch • Shape flat and skewback forms
60 degree with horizontal.
• Depth equal to course of masonry.
• Slight rise of about 10mm to
15mm per metre length of
masonry opening.
• Max.span upto 1.5m
• Used for light loading.

Construction - D’ man civil - R.Theory For Exercise 1.7.38 253

 Name of arch Features Figure
2 Segmental • Centre of arch is below spring
arch line.
• Thrust transferred to the abutment
in an inclined direction

3 Semi-circular • Centre of arch lies on the

springing line
• Skewback is horizontal.
• Thrust transferred to the
abutment in vertical direction.

4 Bull's eye arch • One centre only.

• Used for circular windows

5 Semi -elliptical • More than one centre arch

(Three or five)

254 Construction - D’ man civil - R.Theory For Exercise 1.7.38

Name of arch Features Figure
6 Inverted arch • Constructed between piers to
increase the bearing power of soil.
• Rise is 1/5 to 1/10 of span.
• Built in ½ brick rings.

7 Pointed arch • Two curves meeting at the

apex of a triangle. Two types
are
• Equilateral arch and
• Lancet or isosceles arch.

8 Relieving arch • Constructed over a wooden

joist or flat arch.
• It relieves the joist or flat arch
from carrying load.

9 Horse shoe • Adopted from architectural

arch considerations.
• Shape include more than a
semicircle.

10.Stilted arch • Semi circular portion attached

at the top of two vertical por=tions.
• Springing line passes through
the top of vertical portions.

Construction - D’ man civil - R.Theory For Exercise 1.7.38 255

 Name of arch Features Figure

11 Venetian arch • Depth at crown is more than

that at the springing line.
• Have four centres.

12 Florentine arch • Similar to venetian arch except

that the intrados has a Semi
circular shape.

13 Ogee arch • Consist of three centres and

with reverse (Ogee) curve.

14 Drop arch • Consist of two centres

15 Tudor arch • Consist of four centres.

• This is a pointed arch of four
centres.

256 Construction - D’ man civil - R.Theory For Exercise 1.7.38

Arches according to number of centres
Objectives : At the end of this lesson you shall be able to,
• classify arches according to number of centers
• sketch the various arches with number of centers
• state the features of arches according to the number of centers.

According to number of centers ,the arches are classified

as follows
Classification of arches according to number of centres
Name of arch Description Example
1 one- centered This type of arches have only one Flat, Segmental, Circular, Horse shoe, Stilted, Etc.
arch centre
2 Two- centered This type of arches have two centers Pointed arches ie, Equilateral pointed and
arch isosceles pointed arch (Lancet and Drop).
3 Three-centered This type of arches has three centers Three centered semi-elliptical arch, Florentine
arch arch, Ogee arch.
4 Four-centered This type of arches has four centers Venetian, Tudor.
arch
5 Five-centered This type of arches has five centers Five centered semi elliptical arch.

We can make more types of arches with more number of

centers.

Arches according to material of construction & workmanship

Objectives : At the end of this lesson you shall be able to
• classify arches according to material of construction & workmanship
• state the features of arches according to material of construction
• state the features of arches according to workmanship.
ARCHES

Stone arches Brick arches Concrete arches

1.Rubble arches 1.Rough brick arches 1.concrete block arches

2.Ashlar arches 2.Axed or rough cut brick arch. 2. Monolithic arches
3.Gauged brick arches and
4.purpose made brick arches
Classification of arches according to materials of construction
NAME TYPE OF MATERIALS DESCRIPTION
Stone arch 1 In ashlar masonry • Constructed from wedge shaped units.
2 In rubble masonry • Stones should be laid with their natural
bedding plane.

Construction - D’ man civil - R.Theory For Exercise 1.7.38 257

 NAME TYPE OF MATERIALS DESCRIPTION
• Weak and used for inferior work.
• Span limited to 1m or so
Brick arch 1 With ordinary bricks • Joints are made wedge shaped.
2 With purpose made brick • Not suitable for exposed brick work.
3 With soft brick • Good quality arch work.
• Soft bricks are cut,sawn and rubbed to desired shape.
Concrete arch 1 With precast concrete blocks • Similar to stone arches in ashlar masonry.
2 Monolithic concrete • Constructed from cast in -situ concrete and are suitable
for long spans.

Classification of arch according to workmanship

Name Description
1 Rough arch • Using ordinary uncut bricks
• Bricks are rectangular shape and mortar joints are wider at extrados
than at the intrados.
• Rough arch is used where appearance is secondary importance,
the arch surface is plastered.
2 Axed or rough • The bricks used are wedge shaped by means of an axe
cut arch
• The thickness of mortar joints varies 3 mm to 6 mm.
3 Gauged arch • The bricks used are wedge shaped by means of a wire saw,
the bricks are cut finely.
• The mortar joints are 1.5mm to .75mm

Centering of arches
Objectives : At the end of this lesson you shall be able to,
• define centering of arches
• identify the components of a timber centering
• state the features of centering
• explain removal of centering.

Definition • The whole centering is supported by props.

It is the temporary structure which supports arch during • A pair of folding wedges used to tighten or loosen the
construction or till it attains strength. centering.

Centering of arch • The whole centering parts except props can be replaced

• Timber centering is commonly used because it is Removal centering

simple to erect, dismantle & reuse. • The centering can be removed after attaining sufficient
• Narrow wooden strips known as 'LAGGING' supports strength for arch .
the brick or stone of arch. • For small spans the removal is done by slightly
• Two parallel boards called ‘RIBS’having their upper loosening the wedges
edge shaped to the curvature of arch to support • Spans exceeding 7m or so , bottom of the prop secured
Laggings. in sand box which is filled with sand having a plug.
• The struts & braces strengthen the rib. • To lower the centering remove the plug and the prop
• A horizontal ties provided at lower end of rib to prevent lowered gradually.
from spreading.
• The bearer support the rib.

258 Construction - D’ man civil - R.Theory For Exercise 1.7.38

Construction
Draughtsman Civil - Arches and Lintels R. T. for Exercise 1.7.39 & 1.7.40

Lintels with chajja

Objectives : At the end of this lesson you shall be able to,
• define lintel
• explain bearing of lintel
• list out the materials used lintel
• classify the lintel according to material of construction.

Introduction 1 150 mm or
A lintel can be a load bearing building component placed 2 The height of lintel or
over an opening. The function of lintel is just the same as 3 1/10th to 1/12th span.
that of an arch or a beam. However the lintels are easy
and simple in construction. Lintels are made from various Materials for lintels
materials. The lintels of RCC are widely used to span the The common materials used in the construction of the
openings for doors, windows etc. in a structure. lintel are as follows.
Definition 1 Wood or timber
A Lintel is a structural horizontal member which is placed 2 Stone
across an opening to support the portion of the structure
above it. 3 Brick

Bearing of lintel 4 Steel

Bearing of lintel means the distance up to which it is 5 Reinforced cement concrete

inserted in the supporting wall. Bearing should be the
minimum of the following three considerations.
Classification of lintels according to the material used
Name Features Figure
1 Wood or A single piece of timber or
timber built up sections of wood
lintel. can be used as a
lintel.
• A bearing of about 15 cm
to 20 cm should be
provided.
• The width of lintel should
be equal to the opening
• The depth of lintel should
be about 1/12 to 1/8 of the
span with a minimum
value of 80 mm.
2 Stone These lintels consists of slabs
lintel of stones which it placed
across the openings.
Disadvantages of stone
lintels
• Stone posses low tensile
resistance.
• It is difficult to obtain a good
stone of required depth.

259
 Name Features Figure
3 Brick Brick lintels consist of bricks
lintels which are generally placed on
edge.
• bricks should be well burnt,
copper coloured
• free from cracks and with
sharp and square edges.
• this lintel have a depth
equal to some multiple of
brick courses.
• Suitable up to a span of one
metre and for greater spans
reinforcement or steel angle
may be provided.
4 Steel • steel lintels consist of steel
lintels angles or rolled steel joists.
Steel angles are used for
small spans and light loading.
• Rolled steel joists are used
for large spans and heavy
loading.
• Tube separator-may be
provided to keep the joists
in position.
• R.S.J - The joists are
embedded in concrete to
protect steel from corrosion
and fire.
5 Reinforced These lintels consists of
cement reinforced cement concrete.
concrete The usual mix for concrete
R.C.C lintel is 1:2:4 lintels
lintels Properties of R.C.C
lintels.
• fire proof
• durable
• strong
• economical
• easy to construct
• no relieving arches are
necessary.
The reinforcement provided
depends on
1 span of lintel
2 width of opening
3 total load to be supported
a. Precast • Economical, Increase
RCC speed of construction
• Allow sufficient time for
curing before fixing.
260 Construction - D’ man civil - R.Theory For Exercise 1.7.39 to 1.7.40
Name Features Figure
b. Cast in situ • Centering is prepared
RCC Lintel reinforcement is placed and
concreting is done.
6 Reinforced Brick lintel strengthened by
Brick lintel the provision of mild steel. In
this use first class bricks with
high compressive strength.
Dense cement mortar is used
to embed the reinforcement.
It is adopted or used in the
following circumstances.
• Brickwork has to bear
tensile and shear stress
• To increase the longitudinal
bond
• Brickwork supported on
large settlement soil.
• Brickwork is supported to
act as a beam or lintel over
opening
• When brickwork is to resist
lateral loads as in retaining
walls
• To carry heavy compressive
load
• In seismic areas

7 R.C.C. lintel • The number of main bars

with chajja depends upon the load to
or canopy be carried from the wall above
and span of opening.
• The diameter of the bar varies
with the span and is adopted
as follow
• 6 mm φ bar span upto 1 m
• 8 mm φ bar span 1 to 1.5m
• 10 mm φ bar span 1.5 to 2 m
• 12 mm φ bar span 2 to 3 m
• The details of chajja
projection or canopy is
shown in Fig. 7

Construction - D’ man civil - R.Theory For Exercise 1.7.39 to 1.7.40 261