MCQs

1)The surface of freshly cut timber should be:

a) Soft and shining
b) Hard and shining
c) Perfectly round
d) Light in colour
Answer: b

2)The quality of timber does not depend upon:

a) Maturity of tree
b) Time of felling
c) Type of tree
d) Size of tree
Answer: d

3)Bitumen is obtained from __________

a) Wood
b) Petroleum
c) Coal
d) Kerosene
Answer: b

4)The resistance to flow is measured by __________

a) Flash and fire
b) Viscosity
c) Penetration test
d) Ductility test
Answer: b

5)What is concrete?
a) A mixture of homogenous materials
b) A mixture of material and hydrogen
c) A mixture of cement and hydrogen sulphide
d) A mixture of cement, water, and aggregates
Answer: d
6)Which type of concrete is classified based on the design of concrete?
a) Plain
b) Reinforced
c) Prestressed
d) All of the above
Answer: d
7)__________ has designated the concrete mixes into a number of grades as M10, M15.
a) IS 456-2000
b) IS 456-2010
c) IS 513-1999
d) IS 465-2000
Answer: a

8)What is the approx. mix proportion for M20?

a) 1:3:6
b) 1:2:4
c) 1:1.5:3
d) 1:1:2
Answer: c
9)Which of the following property of a substance that resists abrasion or scratching that causes
penetration or indentation?
a) Hardness
b) Stiffness
c) Toughness
d) Strength
Answer: a

10)Which of the following is not a type of Non-destructive testing?

a) Ultrasonic test
b) Eddy current testing
c) Compression testing
d) Visual testing
Answer: a

11)How should be the colour of good quality timber?

a) Light
b) Gradient
c) Dark
d) Brown
Answer: c
12) Which of the following polymer type is not classified on the basis of its application and
properties?
a) plastics
b) rubbers
c) synthetic
d) fibres
Answer: c
13) Which of the following polymerization is also known as pearl polymerization?
a) emulsion polymerization
b) suspension polymerization
c) solution polymerization
d) bulk polymerization
Answer: b
14) Tar is obtained from __________
a) Wood
b) Petroleum
c) Coal
d) Kerosene
Answer: a
15)Which bitumen does not need heating?
a) Paving grade
b) Cut back
c) Modified
d) Bitumen emulsion
Answer: b
16) What is the importance of the Standard Consistency Test?
a) It is used to determine the quality of water
b) It is used to determine the quality of aggregates
c) It is used to determine the quality of cement
d) None of the above
Answer: a
17) What is the approx. mix proportion for M25?
a) 1:3:6
b) 1:2:4
c) 1:1.5:3
d) 1:1:2
Answer: d
18) High strength concrete is defined purely on the basis of ____________
a) Tensile strength
b) Compressive strength
c) Good Aggregrates
d) Poor Aggregrates
Answer: b
19) The cement concrete, from which entrained air and excess water are removed after placing it in
position, is called _________
a) Vacuum concrete
b) LWC
c) Prestressed concrete
d) Sawdust concrete
Answer: a
20) Aerated Concrete is ______________
a) Very heavy weight
b) Heavy weight
c) Medium weight
d) Light weight
Answer: d

MST-1

Q2) write in brief on [i] testing on concrete [ii] bulking of sand [iii] lime mortar

Ans [i] testing of concrete - In testing, the aim is to determine quality. The testing of concrete,
concrete masonry, and their reinforcement is commonly used by design professionals during
structural assessment and retrofit planning. The testing of materials may be performed to
supply routine information on the quality of a products (control testing), to develop new or
better information on known materials or to develop new materials, or to obtain accurate
measures of fundamental properties or physical constants.

Testing of concrete is vital to ensuring the strength and resilience of built structures. Testing
of concrete materials can be divided into two primary categories: field testing and laboratory
testing.

Field Testing of Concrete

Field testing of concrete can occur during concrete installation or during investigative
evaluations of installed concrete to determine strength qualities.

Concrete Slump Tests

Air Content Testing

Unit Weight
Lab Testing of Concrete
Tests for compressive strength and flexural strength are best done through
destructive testing in a laboratory.

Compressive Strength Lab

TestTensile or Flexural Testing of Concrete

Ans [ii] bulking of sand - Bulking of sand or fine aggregate is the

phenomenon of increase in sand volume due to the increase of moisture
content. The moisture content in the sand makes thin films around sand
particles. Hence, each particle exerts pressure. Thus they move away from
each other causing an increase in volume.

The increase in the volume of sand due to increase in moisture content is known as bulking of sand.
A film of water is created around the sand particles which forces the particles to get a side from each
other and thus the volume is increased.
The increase in moisture in sand increases the volume of sand. The volume increase in dry sand is
known as the bulking if sand. Bulking of sand depends on the quantity of moisture in the sand and
also the size of the particles. Five to eight percent of the increase in moisture in the sand can
increase the volume of sand up to 20 to 40 percent. Again the finer the sand is more will be the
increase in volume and increase in volume will be relatively less for coarser sand.

Ans[iii] lime mortar - Lime mortar or torching[1][2] is composed of lime and an aggregate such as
sand, mixed with water. The ancient Egyptians were the first to use lime mortars, which they used to
plaster their temples. In addition, the Egyptians also incorporated various limes into their religious
temples as well as their homes. Indian traditional structures built with lime mortar, which are more
than 4,000 years old like Mohenjo-daro is still a heritage monument of Indus valley civilization in
Pakistan.[3] It is one of the oldest known types of mortar also used in ancient Rome and Greece,
when it largely replaced the clay and gypsum mortars common to ancient Egyptian construction.[4]

Lime Mortar

Lime mortar is made of lime and an aggregate such as sand, which is mixed with water, Ancient
Indians first used lime mortar for plaster temples.

It is primarily used in the conservation of buildings initially constructed using lime mortar, however,
it may be used as a substitute for ordinary Portland cement.

What Is Cement Used For?

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What Is Cement Used For?

These qualities lead to initial deterioration of soft and old bricks, usually low temperature fired, lime
mortars are recommended to be used.

Properties of Lime Mortar:

 This mortar is relatively plastic and workable when it is wet.

 It has good working properties if made from excessive calcium lime.

 It develops the strength very slowly however achieve strength constantly for a very long
time.

 Also, does not set however it harden, when water is lost by absorption and evaporation by
the blocks.

 It provides a fairly strong surface, when used for plastering.

 It provides the adequate bonding, when used for masonry joints.

Types of Lime Mortar:

1.Hydraulic Lime Mortar:

This mortar is made with Natural Hydraulic Lime (NHL).

It has excellent stability of power and flexibility, available in a variety of strengths to garb absolutely
different applications.

It sets in damp conditions and soon reaches a power preventing frost damage.

On the similar time, it remains softer and sympathetic to the masonry when absolutely cured.

The material is available in powdered form like a modern cement mortar to combine and it is also
the most tolerant of the unconfirmed.

2.Non-Hydraulic Lime Mortar:

This mortar is made with non-hydraulic lime, usually referred to as lime putty.

This mortar is extra soft and versatile, perfect for the conservation of gentle masonry.

It carbonates very slowly, however it leaves frost damage in cold conditions and it is not suitable for
damp conditions.

The material offered as a moist, pre-mixed mortar that is practically unlimited if saved properly.

3.Hot Mixed Lime Mortar:

This mortar is made with quicklime, lots of heat is produced throughout mixing.

This sticky, lime-rich mortar is most popular in constructing preservationists as scorching mixing
however, non-hydraulic lime mortars have a low resistance to frost.

The material is offered as a moist, pre-mixed mortar though it is typically assisted in cold and aged.

4.Pozzolana Mortar:

A pozzolana will be added an “air lime” mortars to make hydraulic setting characteristics.

A preliminary hydraulic set drives initial strength and it can introduce some frost resistance in non-
hydraulic and hot-mixed lime mortars.

Advantages of Lime Mortar:

1. It reduces the need for movement joints.

2. Makes use of much less energy to produce than cement.

3. Re-absorbs the CO₂ when it cures and sets.

4. It also permits masonry to be recycled at the finish of life.

5. It provides a breathable type of construction.

6. Also provides a water-shedding barrier for walls.

7. It enhances brickwork and various masonry.

8. This mortar has constant prime quality and color of the mortar.
 9. These mortars might be re-worked for up to 24 hours.

10. Also reduces wastage when using a silo structure.

Disadvantages of Lime Mortar:

1. Quick setting time limits the time obtainable.

2. Some cement contains appreciable quantities of soluble salts, particularly potassium sulfate
which may become a supply of salt loss to the stonework.

3. The use of cement leads the consumer to deal with gold lime mortars as it has been purely
hydraulic lime or cement.

4. An excessive amount of initial chemical set ignores the importance of extended carbonation
of the non-hydraulic component.

5. There is a risk of separation causing the cement to separate from the lime because the
mortars dry and hardens.

Uses of lime mortar:

 Fats lime mortars can be used in all types of foundation work that is in dry subgrade i.e.

water table 2.4 meters under the foundation level.

 Fats lime and hydraulic lime are both appropriate for all masonry works.

 Lime mortars could be replaced with cement mortars.

 Additionally used to bind stones, bricks, or concrete blocks together.

 Lime mortars cannot be used when the subgrade soil is moist or the water table is within 2.4
m.

 Heavy loading is expected.

 The construction is very large and very rough.

Also read: Types of lime, Types of mortar & Lime plaster

Conclusion:

Natural lime mortar is flexible, thus allowing movement into the building and prevents cracks in the
masonry.

In addition, they are breathable (vapor permeable), drawing the vapor present in the masonry back
into the air.

Q3) explain the thermal properties of concrete ?

Ans) Thermal Properties

 
Thermal properties of concrete to understand the behavior of concrete to heating
and cooling.The study of thermal properties of concrete is an important aspect
while dealing with the durability of concrete.
 
Concrete is a material used in all climatic regions for all kinds of structures.The
important properties that will be discussed are:
 
� Thermal conductivity
� Thermal diffusivity
� Specific heat
�Coefficient of thermal expansion
 
1Thermal Conductivity
 
This measures the ability of material to conduct heat. Thermal conductivity is
measured in joules per second per square meter of are conductivity of concrete
depends on type of aggregate a of body when the temperature difference is
1degree C per meter thickness of the body.
 
The conductivity of concrete depends on type of aggregate moisture content,
density and temperature of concrete. When the concrete is saturated, the
conductivity ranges generally between about 1.4 to 3.4 J/S/m2
 
2 Thermal Diffusivity
 
Diffusivity represents the rate at which temperature changes within the concrete
mass. Diffusivity is simply related to the conductivity by the following
equation:
 
Diffusivity=Conductivity/CP
 
Where C is the specific heat, and P is the density of Concrete. The range of
diffusivity of concrete is between 0.002 to 0.006m2/h
 
3Specific heat
 
It is defined as the quantity of heat, required to raise the temperature of a unit
mass of a material by one degree centigrade. The common range of values for
concrete is between 840 to 1170 j/kg3/C
 
4Coefficient Thermal Expansion
 
It is defined as the change in unit length per degree change of temperature. In
concrete, it depends upon the mix proportions. The coefficient of thermal
expansion of hydrated cement paste varies between 11x10^-6 and 20x10^-6 per
degree C. The coefficient of thermal expansion of aggregates varies between
5x10^6 and 12x10^-6 per degree C Limestone and Gabbros will have low
values and gravel and Quartzite will have high values of coefficient of thermal
expansion.

Q4) what is curing ? how it is done ? how does it influence the strength of concrete ?

Ans) Curing is the process to control moisture loss during hydration of cement. Hydration takes time
– days, or even weeks rather than hours. To achieve its potential strength and durability, curing
needs to be done for an ideal period of time.

Purpose of Curing

The reaction between cement and water is called hydration. It is an exothermic reaction (which
releases heat). After adding water to the concrete mix, hydration starts, which tends to dry the
concrete quickly. Hence concrete is kept moist by curing, to stop it from drying out before attaining
its maximum strength.

--Water curing prevents the water loss from the concrete surface by uninterrupted wetting of the
exposed surface of concrete. It’s done by spraying or sprinkling water or curing agents over the
concrete surface to ensure that the concrete surface is continuously moist. Moisture from the body
of concrete is retained from evaporating and contributes to the strength-gain of concrete.

Water curing methods are:

Ponding

Sprinkling, fogging & mist curing

Wet coverings

Curing the concrete roof slab

Curing the concrete roof slab

Membrane Curing

Membrane curing lessens moisture loss from the concrete surface by wrapping it with an
impermeable membrane. Curing compounds are wax, acrylic and water based liquids. These are
sprayed over fresh concreting to create an impermeable membrane this will reduces the loss of
wetness from the concrete.

Membrane curing methods are:

Plastic sheeting

Formwork

Steam Curing

Steam curing keeps the surface moist and raises the temperature of concrete to quicken the rate of
strength achievement. It is a process done to speed up the early hardening of concrete and mortars
by subjecting it to steam and humidity. This method is most commonly used for precast concrete
plants where products are mass-produced and the turnaround or striking time of the formwork is
very quick.
steam curing in precast plant - Curing of Concrete

Steam curing in precast plant – Curing of Concrete

It is witnessed that at construction sites, curing of concrete is left to the decision and comfort of the
unskilled manual worker. Site engineers and supervisors should put additional effort to guarantee
that curing is not overlooked at site. They should arrange for the essential resources to retain
satisfactory levels of curing, by using best techniques available.

--Curing plays an important role on strength development and durability of concrete. Curing
takes place immediately after concrete placing and finishing, and involves maintenance of
desired moisture and temperature conditions, both at depth and near the surface, for
extended periods of time. Properly cured concrete has an adequate amount of moisture for
continued hydration and development of strength, volume stability, resistance to freezing
and thawing, and abrasion and scaling resistance.

Q5) explain the process of segregation and bleeding ?

Ans) What is Segregation in Concrete?

Workability is an important property of concrete that reflects how easily we can
place a particular concrete mix . Good concrete should be uniformly mixed and
easily placeable without segregation or bleeding.

What is segregation?

Segregation of concrete is the separation of ingredients in concrete. Since

concrete is a non-homogeneous material, improper mixing is the main reason
for the segregation. It occurs during transporting, handling and placing of
concrete. Also, it affects the concrete properties. The strength of concrete
decreases and leads to cracking. Therefore it should be properly mixed before
use in construction. 
 segregation

Causes of Segregation in Concrete

A good quality concrete mix is prepared by considering factors like the size of
aggregate, water-cement ratio, compaction, etc. They are many reasons for the
causes of segregation. They are

 Improper mixing of concrete ingredients

 Excess use of water 
 Poorly grading of aggregates
 difference in the aggregate sizes 
 Due to improper handling of concrete
 Difference in the specific gravity of aggregates
 Improper vibration of concrete
 Placing of concrete from greater heights 
 Improper transporting of concrete
 Long time Mixing of concrete
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Prevention of segregation is very important as it adversely affects the properties

of concrete. 

Types of Segregation
Segregation occurs in three types such as

1. Separation of water and cement from other ingredients

2. Segregation of coarse aggregate
3. Separation of water content
Segregation is hard to measure since there is no particular test for determining
it. However, the Flow table test measures the segregation. Also, the slump test of
concrete can give an idea about segregation. Coarse aggregate in concrete tends
to settle down from other ingredients. Usually, It occurs when the concrete mix
is dry. While segregation by separation of water content occurs due to an
insufficient amount of fine aggregates or due to the use of an excess amount of
water content.

Bleeding
Segregation occurs when the principal ingredients in a concrete mix – in other
words, gravel aggregate, cement, and water – separate prior to and during the
curing process. Moreover, Segregation causes excessive amounts of water to
rise to the surface. This process is know as bleeding. Bleeding is also similar to
segregation in which the water in the concrete rises to the surface of the
concrete. As a result, the concrete becomes porous and weak.

Bleeding affects its strength and its durability of concrete . Likewise, It breaks the
bond between the concrete and steel reinforcement. However, a proper
proportion of concrete ingredients and controlled vibration can reduce bleeding.
Moreover, air entraining admixtures can also be used for reduce bleeding. 

Bleeding of
concrete

Causes of bleeding in concrete

The main causes of bleeding in concrete mix is as follows

 Segregation is the main cause of bleeding in concrete

 High water cement ratio causes bleeding.
 Type of cement used and quantity of fine aggregate
 Over vibration

How to reduce bleeding in concrete?

By adapting the following methods bleeding can be reduced

 Minimum water cement ratio should be maintained.

 A proper design mix
 Use mineral admixtures like fly ash
 Use air entrapping admixtures
 Maintain fine aggregate ratio

Q6) Explain the special categories of admixtures.

Ans) Admixtures are added to the concrete mix to reduce water content, accelerate or decelerate the
setting property, make concrete light and modify concrete properties. They are added immediately
before or during the mixing of concrete. Excessive amount of water may lead to excessive bleeding
and segregation that is why admixtures are added to control such constituents of concrete. This
imbalance makes the concrete weak and the strength will also be affected. Many admixtures provide
the combination of Superplasticizers, plasticizers or air entrainers. In laboratories, the admixtures are
added during concrete preparation but in field not much time can be given on mixing and making
concrete appropriate for using quickly. Hence, admixtures are added in cement clinkers formation and
then transported to the site for ready to use.

Earlier version of IS codes did not have design steps on special concretes but the new version i.e., IS
10262:2019 has all the details of design steps with admixtures to produce special concrete. Even
solved examples for self-compacting concrete or high strength and high-performance concretes are
there in the new version that shows how mix design can be done.
Admixtures can be of two types – natural and chemical admixtures. Natural admixtures
include rice husk, egg mix, flour, ghee, etc. while chemical admixtures include GGBS, fly
ash, pozzolana and so on. Earlier natural admixtures were widely used and the structures
made with them still remains strong today, but the cost was the factor and not much
modifications could be done with these. The use of chemical admixtures brough about
variation in the construction industry that facilitated the production of self compacting
concrete, high strength concrete, high performance concrete and so on, with the help of these
chemical admixtures.
TYPES OF CHEMICAL ADMIXTURES
These are normally categorised as follows –
1. Plasticizers or water reducing agents
2. Superplasticizers or high range water reducers
3. Accelerators
4. Retarders
5. Air entrainers
6. Others

1. Plasticizers – These are used to improve the plasticity of fresh concrete by reducing water
content without affecting the workability and water cement ratio. Types of plasticizers include
calcium, sodium, ammonium lignosulphonates, polyglycol esters and so on. They are used in
the amount of 0.1% to 0.4% by weight of cement. When these are added they get adsorbed on
the cement particles. This creates repulsive force which is called zeta potential and it depends
upon the amount of plasticizer used. Thus, the structure or texture changes from flocculated to
disperse one and the trapped water inside the flocs gets released, that mixes and fluidifies. The
plasticizers that are adsorbed on the surface of cement particles restrict the hydration of
cement. The plasticizers decrease as the polymer gets entrapped in hydration products. Not
only that, they increase the slump of concrete mix. They also have the capability of reducing
water content upto an extent of 10%. They improve ability of pumping and maintain strength
without effecting the structure.

2. Superplasticizers– They are chemically different from plasticizers. It has similar properties
as that of plasticizerbut is more enhanced and is widely used in production of high strength
concrete. Superplasticizers should be added just before placing otherwise a rapid loss of
workability is observed when these are added to produce flowing concrete. C3A, which is a
constituent of cement, has major influence on superplasticizers. Higher dosage of
superplasticizers facilitates finer cement content that helps in producing high strength
concrete, self-compacting concrete and high-performance concrete. Superplasticizers have the
capability of reducing water content upto the extent of 20% to 40%. With increase in
superplasticizer higher molecular mass can be observed. They have the capacity to
 Produce much more workable concrete maintaining same water-cement ratio.
 Produce same workability for low water-cement ratio.
 Reduce cement content by lowering water cement ratio thereby increasing strength.
Some examples are – naphthalene sulphonates formaldehydes condensates, modified
lignosulphonate, sulphonated melamine formaldehyde and so on.

3. Air entrainers – Air entrainers induce air in the form of bubbles and distribute it evenly
throughout the cement paste. They are used where resistance of concrete is to be increased for
protection of concrete against freezing and thawing. In harsh and lean mixes, they make the
concrete mix more workable. They are also used to reduce bleeding and segregation that
damages the concrete. Their dosage can be estimated as- 1% of air may lead to 5% loss of
strength. They make the concrete light and reduce the dead load of the structure. Whenever
excessive air is induced then application of ground blast furnace slag and fly ash can reduce
the air content.
Main types of air entrainers include animal or vegetable fats, salts of wood resin, sulphonated
hydrocarbons and so on. Other uses of Superplasticizers include –
 Decreases the permeability in concrete.
 Increases resistance to chemical attack.
 Reduces aggregate content.
 Reduces heat of hydration.
 Makes the mix economic.
 Reduces alkali and aggregate reaction.
 Facilitates early placing and finishing.
 Reduces modulus of elasticity and unit weight of concrete.

4. Accelerators–These admixtures speed up the setting property of concrete mix and result in
early gain of strength. Rapid setting is required in case of marine structures or where fast pace
of work is required for early completion of a structure. They are also used in cold areas where
setting takes longer time than usual. Some examples of accelerators are calcium chloride,
sodium chloride, sodium sulphite, sodium hydroxide, sodium carbonate, potassium hydroxide,
potassium sulphate and so on. Among these, calcium chloride is not used in reinforced
structure, and water-retaining structure. This is because it promotes of corrosion of steel and
when reinforcement in concrete come in contact with air or water then it facilitates oxidation
that leads to corrosion. Accelerators work effectively in low surrounding temperature.

5. Retarders – These admixtures lower the setting property of concrete and slow down the
chemical reaction between cement and water, leading to slow rate of gain of strength. Such
retarders are used when cement mix is to be transported in distant places or in hot weather
conditions where setting of concrete mix takes place quickly making it difficult to work or
reduces workability. They are also used to prevent cold joints that occur because of duration
of placing. Some examples of retarders are – sugar, lignin, hydroxylated carboxylic acids,
phosphates, cellulose and so on. Some disadvantages of this includes that they increase plastic
shrinkage often and result in cracking. Also, if addition time is delayed then retardation gets
further extended.

Q7) what is ferrocement concrete ? write down advantages and disadvantages of ferrocement
concrete mass.

Ans) Ferrocement is a thin reinforced concrete structure in which the cement mortar mix is
reinforced with a small diameter wire mesh. 
Ferro Cement increase tensile strength and ductility of concrete due to use of small diameter
wire mesh.  Thus, concrete tensile strength, resistance against cracks, toughness, im-
permeability, fatigue resistance increases.
Generally ferro means iron and cement is a construction bonding material.
The use of fibers in britle materials has been known for years. In the old days, carts used with
bamboo strips in the mud walls and grass fibers in the mud on the walls. 
 Often, a Steel skeleton is also kept with the wire mesh.  Which Holds the wire mesh in its
position and increases the tensile Strength of Concrete.

Properties of Ferrocement
 Highly versatile form of reinforced concrete.
 It's a type of thin reinforced concrete construction, in which large amount of small
diameter wire meshes uniformly throughout the cross section.
 Mesh may be metal or suitable material.
 Instead of concrete Portland cement mortar is used.
 Strength depends on two factors quality of sand/cement mortar mix and quantity of
reinforcing materials used.

Constituent Materials for Ferrocement

1. Cement
2. Fine Aggregate
3. Water
4. Admixture
5. Mortar Mix
 6. Reinforcing mesh
7. Skeletal Steel
8. Coating
Advantages

 Basic raw materials are readily available in most countries.

 Fabricated into any desired shape.
 Low labour skill required.
 Ease of construction, low weight and long lifetime.
 Low construction material cost.
 Better resistance against earthquake.
Disadvantages

 Structures made of it can be punctured by collision with pointed objects.

 Corrosion of the reinforcing materials due to the incomplete coverage of metal by mortar.
 It is difficult to fasten to Ferrocement with bolts, screws, welding and nail etc.
 Large no of labors required.
 Cost of semi-skilled and unskilled labors is high.
 Tying rods and mesh together is especially tedious and time consuming
Q8) discuss the workability of concrete and their tests used in concrete .

Ans) Workability is a property of raw or fresh concrete mixture. In simple words, workability means
the ease of placement and workable concrete means the concrete which can be placed and can be
compacted easily without any segregation. 
Workability is a vital property of concrete and related with compaction as well as strength.
The desired workability is not same for all types of concrete. More workability is required for
a thin inaccessible section or heavily reinforced section rather than a mass concrete body.
Hence, we can’t set a standard workability for all casting works. 
Compaction and workability are very close to each other. Workability can also be defined as
the amount of useful internal work necessary to produce full compaction.
Workability is the property determining the effort required to manipulate a freshly mixed
quantity of concrete with minimum loss of homogeneity
ASTM C 125-93
Workability is that property of freshly mixed concrete or mortar which determines the ease
and homogeneity with which it can be mixed, placed, consolidated and finished
American Concrete Institute (ACI) Standard 116R-90 (ACI 1990b)
Reason for Different types of definition
A variety is seen between definitions of workability because it is not very accurate scientific
term like specific gravity or weight. All definitions are qualitative in nature and personal
viewpoint is reflected instead of scientific precision. There are some other terms used to
describe concrete as cohesiveness, consistency, flowability, mobility, pump-ability etc. These
terms have their specific meaning but they cannot be determined inaccurate number or unit.
Types of Workability of Concrete
Workability of concrete can be classified into following three types:
1. Unworkable Concrete: An unworkable concrete also known as harsh concrete, is a
concrete with a very little amount of water. The hand mixing of such concrete is
 difficult. Such type of concrete has high segregation of aggregates. and it is very
difficult to maintain the homogeneity of concrete mix.
2. Medium Workable concrete: Medium workable concrete is used in most of the
construction works. This concrete is relatively easy to mix, transport, place, and
compact without much segregation and loss of homogeneity.
3. Highly Workable Concrete: This type of concrete is very easy to mix, transport,
place and compact. It is used where effective compaction of concrete is not possible.
The problem is that there are high chances of segregation and loss of homogeneity in
highly workable concrete.
Desirable Workability for Construction
Desirable workability depends on two factors which are:
1. Section size, amount and spacing of reinforcement: When a section is narrow,
complicated, several narrow corners, inaccessible parts; a highly workable concrete is
desirable to obtain full compaction through a reasonable amount of effort. When the
section is crowded with steel reinforcement and spacing of bars is relatively small,
compaction can be difficult and hence highly workable concrete is recommended in
such cases. If there are no limitations of the critical section or heavy reinforcement,
we can get a wide range of workability for concrete casting.
2. Method of compaction: If concrete is compacted manually, more workability is
recommended because hand compaction is not very much uniform and effective. If
there is a scope of the vibrator or machine compaction, we can choose workability
from a wide range.
Strength of Concrete & Workability Relationship
The strength of concrete is the most important property for us. It depends on density ratio or
compaction and compaction depend on sufficient workability. Fresh concrete must have a
workability as compaction to maximum density is possible with a reasonable amount of work.

Figure: Compressive strength vs w/c ratio of

concrete. Source: theconstructor.org
But excessive workability can lessen compressive strength. From the above graph, we see that
compressive strength of concrete decreases with increase in w/c ratio. An increase of w/c ratio
indicates an increase of workability. Hence, the strength of concrete inversely proportional to
the workability and too much workability should be avoided.
Methods of Improving Workability of Concrete
To increase workability there are some ways like:
 Increasing water/cement ratio
 Using larger aggregate
 Using well-rounded and smooth aggregate instead of irregular shape
  Increasing the mixing time and mixing temperature
 Using non-porous and saturated aggregate
 With addition of air-entraining mixtures
 Adding appropriate admixtures

Types of Tests for Workability

of Concrete
 Slump Test
 Compacting Factor Test
 Flow Test
 Vee-Bee Consistometer Test
 Kelly Ball Test

01. Slump Test   

The concrete slump test or slump cone test is the most common test
for workability of freshly mixed concrete  which can be performed
either at the working site/field or in the laboratory. To maintain the
workability and quality of fresh concrete, it is necessary to check batch
by batch inspection of the concrete slump. This can be easily done with
the concrete slump test. The slump test is the simplest test to determine
workability of concrete that involves low cost and provides immediate
results.
Recommended Result of Concrete Slump Test  
As per IS 456:2000 (Plain and Reinforced Concrete -Code of Practice),
 If the slump of the concrete is in between 0 to 25 mm than it is considered
as very low workability of concrete,
 If the slump of the concrete is in between 25 to 50 mm than it is considered
as low workability of concrete,
 If the slump of the concrete is in between 50 to 100 mm than it is
considered as medium workability of concrete,
 If the slump of the concrete is in between 100 to 150 mm than it is
considered as high workability of concrete.
Standard Guidelines for Concrete Slump Test    
There are various standard guidelines available to perform the concrete
slump test. Such as,

 IS 1199 – 1959,
 ASTM C 143-10,
 BS 1881: 103 :1993 etc.
Slump Test Apparatus  
Following apparatus are used for performing the slump test,

 Slump Test Cone (Mould)

 Tamping rod
 Scale for measurement
 CONCRETE
Concrete Slump Test to check the workability of concrete

Hemali Patel
 March 14, 2019

02. Compaction Factor Test 

Compaction factor test works on the principle of determining the degree
of compaction achieved by a standard amount of work done by allowing
the concrete to fall through a standard height. This is specially designed
for laboratory use, but if the circumstances favours, it can also be used
on the working site/field.
Compaction factor test of concrete is more precise and sensitive than
the concrete slump test; hence it is more favorable and useful for low
workable concrete or dry concrete which is generally used when
concrete is to be compacted by vibration.
 CONCRETE
What is Compaction of Concrete?

Tanvi Lad
 January 19, 2019

Recommended Result of Compaction Factor Test

According to the ‘A.M. Neville ’ (Author of Properties of Concrete),
description of the degree of workability and their compacting factor are
as follows:
 If the compacting factor is 0.78 than it is considered as very low workability
of concrete,
 If the compacting factor is 0.85 than it is considered as low workability of
concrete,
 If the compacting factor is 0.92 than it is considered as medium workability
of concrete,
 If the compacting factor is 0.95 than it is considered as high workability of
concrete.
Standard Guidelines for Compaction Factor Test   
There are various standard guidelines available for performing the
compaction factor test. Mentioned below are the standard guidelines
available,

 IS 1199 – 1959,
 ACI 211.3-75 (Revised 1987),
 BS 1881: 103 :1993 etc.
Compaction Factor Test Apparatus
Following apparatus are used for performing the compaction factor test,

 Compacting factor apparatus – It consist of two conical hoppers and one

cylindrical mould
 Tamping rod
 Weighing machine
 CONCRETE
Compaction Factor Test to Determine the Low Workability of Concrete!

Hemali Patel
 July 12, 2019

03. Flow Test

The flow test is a laboratory test, which gives an indication of the quality
of concrete with respect to consistency or workability and cohesiveness.
In the flow test, a standard mass of concrete is subjected to jolting. This
test is generally used for high/ very high workability concrete.
Similar laboratory test named ‘Flow Table Test ‘was developed in
Germany in1933 and it has been described in ‘BS 1881:105: 1984’. This
method is used for the high and very high workable concrete which
would exhibit the collapse slump.
Recommended Result of Flow Test
According to ‘M.S. Shetty’ (Concrete Technology Theory and Practice),
the value of flow test may range anything from 0 to 150 %.
Standard Guidelines for Flow Test
 There are various standard guidelines available to perform the flow table
test. Mentioned below are the standard guidelines,

 IS 1199 – 1959
 ASTM C 124 – 39 (Reapproved 1966)
Flow Test Apparatus
Following apparatus are used for performing the flow table test,

 Flow table
 Mould
 Scale

CONCRETE
Flow Test of Concrete to Determine High Workability of Concrete!

Hemali Patel
 June 18, 2019

04. Vee Bee Consistometer Test

Vee bee consistometer test is a good laboratory test on fresh concrete
to measure the workability in an indirect way by using a Vee-Bee
consistometer. Vee bee test is usually performed on dry concrete and it
is not suitable for very wet concrete. Vee bee consistometer test
determines the mobility and to some extent compatibility of concrete. In
the vee bee consistometer test vibrator is used instead of jolting. Vee
 bee test determines the time required for the transformation of concrete
by the vibration.

Recommended Result of Vee Bee Consistometer Test   

According to ‘IS 1199:1959’ (Methods of Sampling and Analysis of
Concrete),
 If vee bee time is up to 20 to 15-10 seconds than concrete is considered as
in a very dry consistency.
 If vee bee time is up to 10 to 7-5 seconds than concrete is considered as in
a dry consistency.
 If vee bee time is up to 5 to 4-3 seconds than concrete is considered as in a
plastic consistency.
 If vee bee time is up to 3 to 2-1 seconds than concrete is considered as in a
semi-fluid consistency.
Standard Guidelines for Vee Bee Consistometer Test
There are various standard guidelines available to perform the vee bee
test. Mentioned below are standard guidelines for Vee Bee
Consistometer test,

 IS 1199 – 1959
 ACI 211.3-75 (Revised 1987)
 BS EN 12350-3: 2009.
Vee Bee Consistometer Test Apparatus
Vee bee consistometer is used to perform the vee bee test of concrete,
which consists of the following components,

 Vibrating table
 A Metal pot
 A steel metal cone or Slump Cone
 A standard iron rod
To know the test procedure and result calculations, read Vee Bee Test .
 05. Kelly Ball Test (Ball
Penetration Test)

This test is developed by J.W Kelly, hence it’s known as a Kelly ball test.
Kelly ball test is a simple and inexpensive field test which measures
workability of fresh concrete with the similar to the concrete slump test,
but it is more accurate and faster than a slump test. This test uses a
device that consist of metal hemisphere (ball) thereby indicating the
consistency of fresh concrete by its level of penetration when the metal
hemisphere drops. Thus, in this test, depth is determined through metal
hemisphere, which sinks under its own weight into fresh concrete.
 Standard Guidelines for Kelly Ball Test
There is a standard guideline available to perform the Kelly ball test.
Mentioned below are standard guidelines for Kelly Ball Test,

 ASTM C360-92 – For ball penetration test

Kelly Ball Test Apparatus
Kelly ball test apparatus is used to perform the Kelly ball test, which
consists of the following components,

 Metal hemisphere (Ball)

 Graduated Scale
 Handel
 Frame
Read, Kelly Ball Test to Measure Workability of Concrete ! In the
mentioned link, we have described in detail its test procedure, and
calculations of result.

Q9) explain the concept of ‘mix design’ pertaining to concrete.

Ans) What Is Mix Design?

Concrete mix design is a procedure of manufacture of concrete with an ideal
proportion of ingredients to fulfill the desired strength & sturdiness of
the concrete structure.

Concrete is generally a blend of cement, sand & aggregates. Bridges, dams

require an oversized amount of concrete, utilizing it incorrect quantity makes
the structure economical.

Hence, to find the proper quantity of cement, sand & aggregate construction

mix design is required.

Types of Concrete Mix Design

Three different types of concrete mix design are as follows.

1. Nominal Concrete Mix:

Nominal concrete blend are low quality concrete blends utilized for bijou &
unimportant jobs. Superior aggregate quantity is fixed regardless of cement &
coarse aggregate proportions.

Therefore, the standard of concrete blend are varied in range & required

brawn might not be achieved. However, the nominal concrete for
given workability ranges in brawn on account of the discrete combination
of design materials.

2. Designed Concrete Mix:

Designed concrete blends doesn’t possess any specified ranges in
proportions. Planning is done in terms of the necessities of concrete
brawn. So, it is possible to achieve the desirable features of concrete.

Fresh concrete properties like workability, setting time & hardened concrete

properties like compressive strength, durability, etc. are achieved by this
procedure.

Utilization of additives like admixtures, retarders, etc. are done to ameliorate

the properties of blend. The range of grades of concrete can be designed from
as low as M10 grade to loftier grades like M80, M100.

Workability requirements of every blend can be attained utilizing this

procedure from 0 to 150 mm slump. The performance of the concrete is
marked by the designer & combination ratio is set by the manufacturer.
This is the principal rational strategy for the selection of blending ratios with
specific substances, considering discrete features.

The strategy ultimately ends up in manufacturing concrete at a low-cost price.

There is no control test required according to the mass of the substance.

3. Standard Mix:
Nominal blends of constant cement– aggregate proportion range in sturdiness
& will lead to fewer or over-content blends. That’s why, minimal compressive
sturdiness obtained in many features & therefore these blends are referred to
as standard mixtures.

Letter M denotes the amount which is specified by 28-day cubic energy of the

mixture in N/mm2. The mixture grades M10, M15, M20 & M25 approximately
correspond to mixing ratios (1: 3: 6), (1: 2: 4), (1: 1.5: 3) and (1: 1: 2).

Advantages of Mix Design

1. Desired Proportions of Every Ingredient: 

Main goal of the concrete blend design is to search the specified proportion of
every module like cement, coarse aggregate, fine aggregate, water, etc.

2. Quality Concrete Mix: 

Every module utilized in the concrete blend design is examined for its superior
quality. The aggregates with good brawn, shape, relative density & free from
organic content are utilized.
Superior concrete ameliorates its features like brawn, durability, etc. the design
blend which is ready from ideal modules in definite proportions itself
ameliorates the concrete features.

Concrete blend generated is examined utilizing compressive

strength machines, tensile strength machines within concrete cubes &
cylinders.

3. Economical Concrete Mix: 

For generating concrete in nominal mix, cement is employed in place of
other materials to inflict more brawn which affects the price of the project.

It additionally surges the warmth of hydration & causes cracks in concrete. But

by utilizing a mix design, concrete of required sturdiness is designed with the
precise quantity of cement.

It saves the value of the project & an economical concrete blend is derived &
it also shields the formation cracks by lowering heat of hydration.

4. Best Use of Locally Available Material: 

Mix design permits the employment of locally achievable materials like coarse
aggregates, fine aggregates, etc. as long as it’s of eximious quality. This may
diminish the value of the project.

5. Desired Properties of Mix:

The concrete thus achieved possesses features like workability, sturdiness,
setting time, strength, impermeability, etc. Design is done by keeping in mind
a few vital factors like water-cement ratio, gradation of aggregates, etc.

According to the development conditions, admixtures are utilized to

ameliorate the features of concrete. Designed concrete blend fulfills the brawn
requirement of a structure against several tyrannical environmental effects.

Disadvantages of Mix Design

 1. It requires a high initial cost.
2. Also, require skilled labor.
3. Also, requires specific attention.

Uses of Mix Design

Various area uses of mix design are as follows

 Designed to achieve the desired functionality within the plastic phase.

 Determine the minimal energy within the rigid phase.
 Supply concrete at a low cost.

Purpose of Mix Design

 Superior concrete mix design generates the foundation of a sound
infrastructure.
 It is actually is a combination of modules which generates desired
strength & sturdiness for the concrete structure.
 Because every ingredient within the mixture possesses a range of
features, it’s not effortless to prepare a good concrete blend.
 Every one ingredient needs to be tested to note their features &
therefore additionally the bearing capacity of the project location is also
required to be examined.
 Water, fine sand, coarse aggregate, cement, chemicals, reinforcement,
& soil needs to be checked.
 Values derived after testing are utilized for all mix designs. This makes
sure that the structure is able to resist failure.
Conclusion

The rules & blended proportions ought to be done attentively as a bijou

blunder may result in an adverse effect on the structure. Select the suited
ratios of water, cement, fine aggregate, coarse aggregate, admixture for
concrete.

FAQ
Mix Design
Design mix concrete is adopted for high rise constructions. In this type of
mix, the mix ratios are decided by an Engineer after analysing the properties of
individual ingredients of concrete. Like, cement is tested for Fineness modulus
and Specific gravity of cement in the lab while deciding the Design mix ratio.

What Is Mix Design?

Mix design can be defined as the process of selecting suitable ingredients of
concrete and determining their relative proportions with the object of
producing concrete of certain minimum strength and durability as
economically as possible.

Types of Concrete Mix Design

Compressive Strength
Concrete Grade Mix Ratio (Cement : Sand : Aggregates)
MPa (N/mm2) psi
Grades of Concrete
M5 1 : 5 : 10 5 MPa 725 psi
M7.5 1:4:8 7.5 MPa 1087 psi
M10 1:3:6 10 MPa 1450 psi
M15 1:2:4 15 MPa 2175 psi
M20 1 : 1.5 : 3 20 MPa 2900 psi
Standard Grade of Concrete
M25 1:1:2 25 MPa 3625 psi
M30 Design Mix 30 MPa 4350 psi
M35 Design Mix 35 MPa 5075 psi
M40 Design Mix 40 MPa 5800 psi
M45 Design Mix 45 MPa 6525 psi
High Strength Concrete Grades
M50 Design Mix 50 MPa 7250 psi
M55 Design Mix 55 MPa 7975 psi
M60 Design Mix 60 MPa 8700 psi
M65 Design Mix 65 MPa 9425 psi
M70 Design Mix 70 MPa 10150 psi
Advantages of Mix Design
The concrete obtained through mix design contain desired properties like
workability, durability, setting time, strength, impermeability, etc. The design is
processed by considering some important factors like water-cement ratio,
gradation of aggregates, etc.

Disadvantages of Mix Design

 1. It requires a high initial cost.
2. Also, require skilled labor.
3. Also, requires specific attention.
Application of Mix Design
The object of mix design is to decide the proportions of materials which will
produce concrete of required properties. The mix proportions should be
selected in such a way that the resulting concrete is of desired workability
while fresh and it could be placed and compacted easily for the intended
purpose.

Uses of Mix Design

The object of mix design is to decide the proportions of materials which will
produce concrete of required properties. The mix proportions should be
selected in such a way that the resulting concrete is of desired workability
while fresh and it could be placed and compacted easily for the
intended purpose.

Purpose of Mix Design

The object of mix design is to decide the proportions of materials which will
produce concrete of required properties. The mix proportions should be
selected in such a way that the resulting concrete is of desired workability
while fresh and it could be placed and compacted easily for the
intended purpose.

Shotcrete Mix Design

Shotcrete typically consists of one part cement and four parts sand by
weight with approximately 7% water by mass of dry ingredients. It can
also include coarse aggregate and admixtures. Dry mix shotcrete involves the
premixing of dry ingredients with water added at the nozzle.

MST 2

Q 2) What is polymers ? and define general properties of polymers

Ans . A polymer is a large molecule or a macromolecule which
essentially is a combination of many subunits. The term polymer in
Greek means ‘many parts’. Polymers can be found all around us. From
the strand of our DNA, which is a naturally occurring biopolymer, to
polypropylene which is used throughout the world as plastic.
Polymers may be naturally found in plants and animals (natural
polymers) or may be man-made (synthetic polymers). Different
polymers have a number of unique physical and chemical properties,
due to which they find usage in everyday life.

Properties of Polymers

Physical Properties

 As chain length and cross-linking increase, the tensile strength of

the polymer increases.
 Polymers do not melt, and they change state from crystalline to
semi-crystalline.

Chemical Properties

 Compared to conventional molecules with different side

molecules, the polymer is enabled by hydrogen bonding and ionic
bonding resulting in better cross-linking strength.
 Dipole-dipole bonding side chains enable the polymer for high
flexibility.
 Polymers with Van der Waals forces linking chains are known to be
weak but give the polymer a low melting point.

Optical Properties

 Due to their ability to change their refractive index with

temperature, as in the case of PMMA and HEMA: MMA, they are
used in lasers for applications in spectroscopy and analytical
applications.

Some Polymers and their Monomers

  Polypropene, also known as polypropylene, is made up of
monomer propene.
 Polystyrene is an aromatic polymer, naturally transparent, made up
of monomer styrene.
 Polyvinyl chloride (PVC) is a plastic polymer made of monomer
vinyl chloride.
 The urea-formaldehyde resin is a non-transparent plastic obtained
by heating formaldehyde and urea.
 Glyptal is made up of monomers ethylene glycol and phthalic acid.
 Bakelite or polyoxybenzylmethylenglycolanhydride is a plastic
which is made up of monomers phenol and aldehyde.

Q 3) what are various engineering properties of timber?

Ans. Properties of Timber

The quality of timber must be ensured before using it for a purpose. The
quality can be ensured by investigating the properties of timber. Here we
have discussed both physical and mechanical properties of timber which
affects timber quality.
Followings are the physical and mechanical properties of timber:

 Colour
 Appearance
 Hardness
 Specific Gravity
 Moisture Content
 Grain
 Shrinkage and Swelling
 Strength
 Density
 Toughness
 Elasticity
 Warping
 Durability
 Defectless
 Workability
 Soundness
 Free of abrasion
  These properties are briefly discussed below:
 Colour
 Color is a uniform property by which most trees are characterized
as they show variation from tree to tree. Light color indicates weak
timber. For example, freshly cut teak, Deodar, and Walnut have a
golden yellow, whitish and dark brown shades respectively.
 Appearance
 Smell is a good property as timbers for few plants as they can be
identified by their characteristic aroma. Fresh cut timbers have a
good smell. For example resinous smell from pine.
 Hardness
 For the resistance of any kind of damage, hardness is an obvious
property.
 Specific Gravity
 Variation of timber in specific gravity (0.3-0.9) is found. It depends
on pores present inside timber. The specific gravity of this light
material is less than that of water (<1). But in case of compact
wood where pores are almost absent and become heavier, their
specific gravity increases up to 1.5.
 Moisture Content
 Timbers are hygroscopic and gain water from nature
(atmosphere). The absorption of water or dehydration depends on
atmospheric humidity. If timbers moisture content is high that
means the timber quality is low. Water content is the risk of fungal
attack.
Grain
Several types of grain arrangement found. On the grain structure quality
of timber varies. Grains remain closely related.

1. Straight grain: Arrangement of vascular tissue (xylem and phloem)

is important which grow parallel to the length of the timber that is
termed as straight grain.
2. Coarse grain: vascular tissue and fibre arranged broadly and
widely.
3. Interlocked grain: Instead of parallel arrangement twisted, a spiral
arrangement may be found.
Shrinkage and Swelling
The percentage of shrinkage and swelling varies from plant to plant.
Some give higher percentage after drying. Shrinkage starts when cell
walls of timber start to release water. In moisture atmosphere timber
swells when cell walls absorb water. Good quality timbers swell less.
Timbers having thicker wall swell more than a thinner one.
Strength
Best quality timbers have the highest strength. Strength means capable
to bear loads. Anisotropic material like timber has different structure at
the different portion. So, the strength of timber is different at different
points. Grain structure determines the strength of the timber. Some
types of strength are

1. Compressive strength: 500 kg/cm2 to 700 kg/cm2 load is enough

to test timbers strength.
2. Tensile strength: When timber is enough strong to the tensile
force. If perpendicular force is made then timber is weaker. 500-
2000 kg/cm2 is the range of tensile strength load.
3. Transverse strength: Enough bending strength indicates good
quality timber.

Density
Timber having higher density have a thicker wall. An important property
that quality of timber. Moisture content: Presence of defects: There may
be some of the natural and artificial defects in timber such as cross-
grain, knots, and shakes, etc. All of them cause a decrease in the
strength of the timber.
Toughness
Timber has to have the capability to bear shocks, jerk. Anti-bending and
ant splitting characteristic is needed. Old timbers have annual rings
which indicate their age is a good indicator.
Elasticity
Another property elasticity means timber should attain its own shape
after use. Because of this quality, it is used in sports bat.
Warping
Environmental change with season can’t effect good quality timber.
Durability
A good quality timber has the property to resist the attack the infection of
fungus or other insects. This resistance quality makes timber better.
Defectless
This property is gained if the timber is from a sound tree. A defectless
tree is free from sap, shakes, and dead knots. To know more about
timber defects read: Defects in Timber
Workability
A good timber is always easy to work on it. Easy to drag using saw on
good timber. The finishing can be done well.
Soundness
A good quality timber gives good sound.
Texture
The texture of good timber is fine and even.
Free of Abrasion
Timber should not be damaged by the external environment. It has to
gain the ability to protect its skin.
Q4) define plywood and particle board.

Ans) What is particle board?

Made using sawdust and glue, particle boards are available as sheets for making
particle board furniture. Particle board is a type of engineered wood and is made
from leftovers of wooden products and so it is an example of best out of waste and is
eco-friendly in nature.

  What is plywood?
Made using veneers of wood, plywood is very strong in nature and is used for
making furniture where durability is sought for – for example, beds, sofas, etc.
Plywood is also a type of engineered wood.
 

Particle board vs plywood: The

differences 
 Particle board Plywood
Made of scraps of wood like wood chips, wood shavings,
Made of laminated wood veneer
etc. and adhesive
Weak Strong
Owing to the composition, they cannot hold nails and Owing to the composition, nails and
screws well. hold on well
Has a smooth finish Has a rough finish
Costs between Rs 40 and Rs 50 per sq ft Costs between Rs 50 and Rs 80 per
 
Let us look at the differences in detail between particle board and plywood that will
help us decide on what kind of particle board furniture and plywood furniture we can
use them for.

  Cost of particle board vs plywood

Particle board cost: Particle board is priced between Rs 40 and Rs 50 per sq ft. So,
particle board furniture is more cost effective than plywood furniture. People who are
doing the home décor with a tight budget can opt for particle board readymade
furniture like a shoe shelf, or a small children’s book shelf instead of going for one
made of wood or plywood.
Plywood cost: Plywood is priced between Rs 50 and Rs 80 per sq ft. So, plywood
furniture is more expensive than particle board furniture.

Composition of particle board vs

 

plywood
Particle board composition: As the sawdust on the surface is thin, the surface of
the particle board is compact as compared to its middle layer, making overall particle
board composition not very strong. As compared to plywood, particle board is weak
in nature. However, particle boards are flat and give a very shiny finish.
Plywood composition: Plywood is made of cross-grain texture and glue and can be
moulded into a variety of shapes. The cross grain texture also makes plywood
stronger in nature as compared to particle board. However, the disadvantage is that
the cross-grain texture gives a rough look to the plywood and so wallpapers or even
paint on it may have a very patchy, unclean look.
See also: MDF vs plywood: Which is the best option for your project?

  Maintenance of particle board vs plywood

Particle board maintenance: The smooth and finished texture cannot bear the
impact of the hammer and screws on the particle board. Particle board being made
of sawdust, swells up once it comes in contact with water and gets damaged soon.
Plywood maintenance: As they are rough and tough, they handle all the pressure
of hammer and screws and can be used to make beautiful, durable furniture. Marine
plywood is water resistant and so you can be rest assured that your furniture will be
safe. Also, as they are made of veneered wood, they are lighter in nature and fixing
wheels below even the biggest of furniture will not result in breakage.

Particle board and plywood: Which

 

furniture is best?
Particle board furniture: As they are available at a cheaper price point with a
smooth finish, particle boards are used for fittings and fixtures, on parquet flooring,
for home décor items and as final layer on furniture owing to their smooth finish.
Q5) explain the term “grade” of concrete . write the various advantages and
disadvantages of concrete.

ANS) Grade of concrete, simply put, is the strength of concrete measured after 28 days
of construction. The grade of concrete construction is based on structural integrity and
type of concrete mix. Nominal mix of concrete is generally used in small scale
construction, whereas design mix is used in large scale constructions. 
Here is a table defining different types of concrete grades along with the concrete mix
ratio, and compressive strength.

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Concrete Grade Mix Ratio Compressive Strength

MPa (N/mm2) psi

Normal Grade of Concrete

M5 1 : 5 : 10 5 MPa 725 psi

M7.5 1:4:8 7.5 MPa 1087 psi

M10 1:3:6 10 MPa 1450 psi

M15 1:2:4 15 MPa 2175 psi

M20 1 : 1.5 : 3 20 MPa 2900 psi

 Standard Grade of Concrete

M25 1:1:2 25 MPa 3625 psi

M30 Design Mix 30 MPa 4350 psi

M35 Design Mix 35 MPa 5075 psi

M40 Design Mix 40 MPa 5800 psi

M45 Design Mix 45 MPa 6525 psi

High Strength Concrete Grades

M50 Design Mix 50 MPa 7250 psi

M55 Design Mix 55 MPa 7975 psi

M60 Design Mix 60 MPa 8700 psi

M65 Design Mix 65 MPa 9425 psi

M70 Design Mix 70 MPa 10150 ps

MPa is Measurement for PSI or pounds per square inch. The mix ratio is of cement,
sand, and coarse aggregate. 
Q6) write down about –
Ans . Resin Concrete
Resin concrete is also known as polymer concrete. It is a composite
material consisting of a monomer or resin system i.e., mixed with graded
aggregate and polymerized. Polymer concrete contains
no Portland cement. Different types of grades and polymers can use in
making polymer concrete such as vinyl esters. They also for making
styrene, unsaturated polyester resins, methyl methacrylates, etc. But the
best known and most widely used binder is an epoxy resin. Resin is a
fast-setting material. It has better bond property, high compressive,
tensile, and flexural strength as compared to conventional concrete. It
also has good chemical resistance. Some polymers, however, show
shrinkage during hardening. But this can reduce by increasing the
amount of aggregate filler.

Prestressed concrete 

It is a form of concrete used in construction. It is substantially

"prestressed" (compressed) during production, in a manner that
strengthens it against tensile forces which will exist when in service. [1][2]: 3–
5 [3]
This compression is produced by the tensioning of high-strength
"tendons" located within or adjacent to the concrete and is done to
improve the performance of the concrete in service. [4] Tendons may
consist of single wires, multi-wire strands or threaded bars that are most
commonly made from high-tensile steels, carbon fiber or aramid fiber.[1]: 
52–59 
 The essence of prestressed concrete is that once the initial
compression has been applied, the resulting material has the
characteristics of high-strength concrete when subject to any
subsequent compression forces and of ductile high-strength steel when
subject to tension forces. This can result in improved structural capacity
and/or serviceability compared with conventionally reinforced concrete in
many situations.[5][2]: 6  In a prestressed concrete member, the internal
stresses are introduced in a planned manner so that the stresses
resulting from the imposed loads are counteracted to the desired degree.
Vacuum concrete
It is the one from which water is removed by vacuum pressure after placement
of concrete structural member. Vacuum concrete has high strength and
durability than normal concrete. Water-cement ratio is detrimental for concrete.
We always try to restrict the water-cement ratio in order to achieve higher
strength. The chemical reaction of cement with water requires a water-cement
ratio of less than 0.38, whereas the adopted water-cement ratio is much more
than that mainly because of the requirement of workability. Workability is also
important for concrete, so it can be placed in the formwork easily without
honeycombing. After the requirement of workability is over, this excess water
will eventually evaporate leaving capillary pores in the concrete. These pores
result into high permeability and less strength in the concrete. Therefore,
workability and high strength don’t go together as their requirements are
contradictory to each other. Vacuum concrete is the effective technique used to
overcome this contradiction of opposite requirements of workability and high
strength.