ty civil fifth semester · concept of size, specific gravity, bulk density, water absorption and...

TY CIVIL Fifth Semester

Sanjay Ghodawat Polytechnic, Atigre 1

Subject: Concrete Technology (17504)

Topic 1: Cement

Contents:

1.1 Chemical Constituents of OPC and their effects on properties of OPC, Bogue‟s

compounds and their properties, Hydration of cement. Physical properties of OPC-Fineness,

setting, compressive strength and soundness. Different grades of OPC. 33, 43, and 53 with

specifications of physical properties as per relevant IS codes.

Testing of OPC –field tests and laboratory tests-fineness test, standard consistency test, setting

time test, compressive strength test, soundness test. Storage of cement and effect of storage

on properties of cement.

1.2 Physical properties, I.S. Specifications and field application of following types of cement :-

Rapid hardening cement, Low heat cement, Portland pozzolana cement, Sulphate resisting

cement, Blast furnace slag cement, White cement.

Que1 Enlist ingredients of cement.

Ans:

1. Lime – (CaO) – 60-67%

2. Silica – (SiO2) – 17-25%

3. Alumina – (Al2O3) – 3-8%

4. Gypsum – (CaSO4) – 2-3%

5. Minor compounds in the form of oxides – (Fe2O3, MgO, SO3,

Na2O, K2O) – 0.1-2%

Que2 Enlist four Bogues compounds with their formula and % in OPC.

Ans:

S.No. Name of compound Formula Percentage

1 Tricalcium Silicate (C3S) 3 CaO SiO2 54.1

2 Dicalcium Silicate (C2S) 2 CaO SiO2 16.6

3 Tricalcium Aluminate

(C3A)

3 CaO Al2 O3 10.8

4 Tetracalcium

Aluminoferrite (C4AF)

4 CaO Al2 O3 Fe2

O3

9.1



Que3 Define hydration and hardening of cement.

Ans: Hydration: It is an exothermic chemical reaction which takes place due

to addition of cement and water giving cement paste and heat

evolved about 120 cal/gm of cement.

Hardening of cement: It is the process of gaining strength to cement

due to its hydration.

Que4 What is initial and final setting time of cement?

Ans: Initial Setting Time- It is the time elapsed from mixing of cement

and water up to when IST needle penetrates upto 33-35mm from top of

Vicat‟s mould.

Final Setting Time- It is the time elapsed from mixing of cement and

water upto when FST needle gives just impression on cement paste in

Vicat‟s mould.

Que5 Enlist four field tests for cement.

Ans:

1. The control of fresh cement should be greenish grey.

2. The hand in cement bag should give cool feeling.

3. A pinch of cement should give smooth feeling to fingers.

4. The handful cement should float on water for some time before

its dipping.

5. The sharp edged cake under water should remain sharp edged

even after 24 hrs.

6. The colour of cement should not be changed after burning.

7. The cement should not contain visible lumps in it.

8. The cement roll should give shiny surface after cutting with knife.



Que6 Enlist any 4 precautions to be taken while storing the cement.

Ans: Precautions to be taken while storing the cement are;

1. Bags should not be stacked more than 8-10 bags vertically.

2. Stacking should be lengthwise and widthwise alternatively.

3. Stacking should be 300 mm away from walls with 1 m gap

between two rows for easy handling.

4. Stacking should be on wooden planks 300 mm above ground

floor to avoid dampness.

5. Exhaust fans and windows should be provided for ventilation.

6. Building should be with 150 mm concrete floor and 9” brick walls

Que7 What do you mean by low heat cement and give two properties

and two use of it.

Ans: Low Heat Cement (LHC): It means the type of cement in which

less heat is evolved in exothermic hydration reaction. In this

cement C3S and C3A % is reduced which gives comparatively

lesser heat of hydration than OPC.

Properties of LHC :

i. Fineness = 3200 cm2/gm

ii. Soundness = Less than 10 mm

iii. Initial setting time = 60 minutes

iv. Final setting time = 600 minutes

v. Compressive strength (28 days) = 35 MPa

Uses of LHC :

i. Mass concreting work such as Dam, Bridge

construction

ii. Nuclear power plant

iii. Sea walls and break waters



Que8 Draw labelled sketch of Vicats apparatus with plunger and initial

and final setting time needle.

Ans:

Que9 List four physical properties of cement.

Ans: Physical Properties of Cement:

i. Fineness

ii. Normal or Standard consistency

iii. Initial and Final setting time

iv. Soundness

v. Compressive strength



Topics 2: Aggregates

Contents:

2.1: ………………………………………………. 04 Marks

Requirement of Good Aggregate. Classification of Aggregate according to source, Size

and Shape.

2.2: Properties of fine aggregates : ………………. 08 Marks

Concept of size, specific gravity, bulk density, water Absorption and Bulking.

Determination of fineness modulus and grading zone of Sand by sieve analysis,

determination of silt content in sand and their specification as per IS 383.

Determination of Bulking of sand. Concept of crushed Sand.

2.3 Properties of coarse aggregates: …………….. 08 Marks

Concept of size, shape, surface texture, water absorption, soundness, specific gravity and

bulk density Determination of fineness modulus of coarse aggregate by sieve analysis,

grading of Coarse Aggregates.

Determination of crushing value, impact value and abrasion value of coarse aggregate

with specification.

Que1 Give classification of aggregate w.r.t. shape and size.

Ans: A) Classification of aggregate according to shape:

i. Rounded:

This type of aggregate is completely shaped by attrition or water worn.

Hence it possess 33-35% void ratio. This type of aggregate is not suitable

for concreting.

Example: River or sea shore gravel, desert, sea shore, windblown sand

etc.

ii. Irregular or partly rounded:

This type of aggregate is naturally irregular or partly shaped by attrition.

It possess 35-37% void ratio. Useful for medium quality concrete.

Example: Pit sand and gravel, cuboid rock etc.

iii. Angular:

This type of aggregate contains well defined edges, formed at

intersection of roughly planer faces. It possess 38-41% voids. Best for

concreting: - Crushed rock of all types.



iv. Flaky:

This type of aggregate having small thickness as compared to width or

length. It has highest % of voids. It is suitable for lower grade of

concrete.

Example:- Laminated Rock

B) Classification of aggregate according to Size:

As per size aggregates are divided into two categories:

i. Coarse Aggregate:

The aggregate having size bigger than 4.75mm is considered as coarse

aggregate.

ii. Fine Aggregate:

The aggregate whose size is 4.75mm and less is considered as fine

aggregate

Que2 Define Flaky and Elongated aggregate.

Ans: Flaky aggregate:

The aggregate is said to be flaky when its least dimension is less

than 3/5th of its mean dimension. These aggregates are angular,

having small thickness as compared to width where mean

dimension is the average of size through which the aggregate

passes and the sieve size on which it retained.

Elongated aggregate

The aggregate is said to be elongated when its length is 14/5th

times its mean dimension. These aggregates are angular, having

small thickness as compared to length



Que3 Define flakiness index and elongation index.

Ans: Flakiness index - It is the percentage by weight of particles whose

least dimension (thickness) is less than (3/5)th of its mean dimension

passing through thickness gauge.

Elongation index – It is the percentage by weight of particles whose

greatest dimension (length) is more than (14/5)th of its mean dimension

retained on length gauge.

Que4 Write four reasons why grading of aggregate is necessary.

Ans: The reasons for necessity of grading of aggregate are;

1. As grading of aggregate is analysis of particles, it is essential to

classify aggregates in various categories like well graded, poorly

graded etc.

2. These graded aggregates helps to produce required dense and

compactable concrete.

3. Grading is useful to decide proportions in concrete to fill voids

and to achieve strength of concrete.

4. Graded aggregates require less cement paste for its workability,

which results in economy.

5. The problems like segregation, bleeding can be overcome by

using well graded aggregates.

6. The concrete can give impermeability and smooth finish by the

use of graded aggregates.

Que5 Define terms- specific gravity, bulk density and % water

absorption.

i. Specific gravity: It is the ratio of density of aggregate to the

density to water.

ii. Bulk density: It is the ratio of weight of aggregate (including

voids) to its unit volume.

iii. % Water absorption: It is the ratio of weight of water absorbed

to weight of dry aggregate; measured in percentage.



Que6 Explain step by step procedure for determination of aggregate

crushing value.

Ans: Procedure for determination of aggregate crushing value :

i. Take air dried aggregate passing through 12.5 mm and

retained on 10 mm IS sieve.

ii. Fill it in crushing mould within 3 layers. Compact each layer 25

times using tamping rod.

iii. Calculate the weight of aggregate filled by subtracting

empty weight of crushing mould as W1 gms.

iv. Now, keep the mould under plunger of compression testing

machine and apply load 4 ton per minute for total 10 minutes;

so that aggregate will crush.

v. Sieve the crushed material through 2.36 mm IS sieve and take

the weight of aggregate retained on this sieve as W2 gms.

vi. Finally calculate percentage Aggregate Crushing Value i.e. %

ACV as (W2 / W1) x 100.

Que7 State necessity of supervision for concrete operation.

Ans: Necessity of supervision for concrete operation :

i. Supervision is necessary to complete all concreting operations

in standard manner.

ii. It is necessary to avoid any type of delay in concrete work.

iii. It is also beneficial to reduce wastage of concrete during

concreting.

iv. It is required to get overall quality in concrete work at site

v. Supervision becomes essential in maintaining smooth flow of

concreting operations at each stage of project.

vi. It found very effective in controlling bad workmanship



Que8 Explain with sketch bulking of sand.

i. Bulking of sand means increase in volume of sand due to

surface moisture.

ii. The volume of sand increases with increase in moisture

content up to a certain limit and thereafter it begins to

decrease.

iii. Maximum increase in volume may be up to 20 to 40% when

moisture content is 5 to 10% by weight.

iv. Bulking is due to thin film of water around the sand grains and

the interlocking of air between the sand grains and the film of

water.

v. The film of water produces surface tension and keeps the

sand grains away from each other.

Que9 Explain the experimental procedure to determine silt content of

sand sample.

Ans:

1. Prepare 1% salt solution by adding 10 gm common salt in 1000

ml water.

2. Fill this salt solution upto 50 ml mark in measuring cylinder. Now

add sand sample in it to reach the mixture upto 100 ml mark.



Finally add more salt solution to reach total volume upto 150

ml.

3. Shake the mixture vigoursly in both palms. Now keep it at

room temperature for 3 hours to separate silt layer above

sand sample as shown in fig. 4.

4. Measure the separated volumes of sand and silt as V1

and V2 resp.

5. Calculate the silt content of given sand sample in

percentage as (V2/V1) x 100. The silt content should be

less than 6% as per IS (other than road concrete).

Que10 Describe step by step procedure to determine aggregate impact

value.

i. Prepare the test sample by sieving the given aggregate. The

sample shall pass through 12.5mm sieve and retained on

10mm sieve.



ii. Dry the sample in an oven at temperature between 1000c to

1100c for four hours and cool it.

iii. Fill the cylindrical measure in three layers taking care to tamp

each layer by tamping rod with 25 strokes.

iv. Weigh this sample (A).

v. Remove the sample from the measure and fill it in the metal

cup fixed to base plate. Tamp it with 25 strokes. Weigh the

metal cup. Find the weight of sample (W1) by deducting

weight of empty cup from it.

vi. Raise the hammer till its lower face is 380mm above upper

surface of the sample and allow it to fall freely on the sample

give 15 similar blows at an interval of not less than one second.

vii. Remove the crushed aggregate from the cup and sieve it

through 2.36mm sieve.

viii. Weigh the fraction passing through 2.36mm sieve. (Recorded

as W2)

ix. The fraction retained on the sieve shall also be weighed (W3).

x. If the total weight (w2+w3) is less than initial weight W1 by

more than one gram, the result shall be discarded and fresh

test is made. Two tests shall be carried out.

Aggregate impact value = (W2/W1) X 100

Que11 Explain with neat sketch the experimental procedure to

determine crushing value of aggregates

1. Take the aggregate sample passing through 12.5 mm and

retained on 10 mm I.S. sieve.

2. Fill it in crushing mould in three layers by tamping each layer 25

times with tamping rod.

3. Calculate the weight of aggregate filled in mould by subtracting

empty weight of crushing mould as „A‟ grams.



4. Now keep it under compression testing machine (CTM) with

plunger touching to top of aggregates filled.

5. Apply the load uniformly at a rate of 4 tonne/min for 10 minutes,

so that aggregates will crush into fine particles.

6. Take out crushed sample and sieve it through 2.36 mm I.S. Sieve. Take

the weight of aggregate particles passed through 2.36 mm I.S Sieve as

„B‟ grams.

7. Calculate aggregate crushing value as B/A X 100 in percentage for

given aggregate.



Topics 3: Concrete

Contents:

3.1 Introduction to concrete - ………………….. 08 Marks

Definition of concrete, necessity of supervision for concreting operation, different grades of

concrete (ordinary Concrete, standard concrete and high strength concrete as per

provisions of IS 456- 2000.

Water cement ratio:- Definition of w/c ratio, Duff Abraham w/c law, significance of w/c ratio,

selection of w/c ratio for different grades of concrete prepared from different grades of OPC

as per graphs specified in IS 10262 -1982, maximum w/c ratio for different grades of concrete

for different exposure conditions.

3.2 Properties of fresh and Hardened concrete……..08 Marks

Definition of workability, factors affecting workability of Concrete. Determination of

workability of concrete by slump cone test, compaction factor test. Range values of

workability requirement for different types of concrete works. Segregation, bleeding.

Definition of compressive strength, durability and Impermeability of concrete. Factor

affecting compressive strength, durability and Impermeability of concrete.

3.3 Concrete Mix Design and Testing of Concrete…08 Marks

Objectives of mix design, list of different method of mix design, study of mix design procedure

by I.S. method as per I.S. 10262-1982 (Only procedural steps)

Testing of concrete:-Significance of testing, determination of compressive strength of

concrete cubes at different ages, interpretation and co-relation of test results

Non- destructive testing of concrete:- Importance of NDT, methods of NDT - rebound hammer

test and ultrasonic pulse velocity test, working principle of rebound hammer and factor

affecting the rebound index, specification for deciding the quality of concrete by Ultrasonic

pulse velocity as per I.S. 13311 (part 1 and 2).

Determination of compressive strength of concrete by rebound hammer test as per I.S. 13311,

determination of Quality of concrete by ultrasonic pulse velocity test.

Que1 Define bleeding, segregation, shrinkage and creep.

Ans: Bleeding – It is the one type of segregation in which water came

out on top of concrete surface.

Segregation – It is the separation of concrete ingredients from

each other.

Shrinkage – It is the formation of cracks on concrete due to water

evaporation or evaporation during and after concrete.



Creep – It is the deformation of concrete takes place even after removal

of load by the age of concrete.

Que2 State Duff Abraham’s Law and its equation.

Ans: Duff Abraham’s Law – For workable concrete, the compressive

strength of concrete depends on water-cement ratio.

Expression – S = A/BX

where, S = Strength of concrete

X = water-cement ratio

A, B = Empirical constants

Que3 Define water cement ratio and give two different grade of

concrete with strength value and nominal mix proportion.

Ans: Water cement ratio: It is the ratio of weight of water to weight of

cement.

W/C ratio = Ww / Wc

Different grade of concrete with nominal mix proportion and strength

value :

i. M 10 (1 : 3 : 6) = 10 N/mm2

ii. M 15 (1 : 2 : 4) = 15 N/mm2

iii. M 20 (1 : 1.5 : 3) = 20 N/mm2

iv. M 25 (1 : 1 : 2) = 25 N/mm2

Que4 State two objectives of mix design and list six factors affecting

concrete mix design.

Ans: Objectives of mix design : Mix design is done for following objectives

i. To achieve a specified compressive strength of concrete.

ii. To reduce wastage of concrete by correct proportioning.

iii. To achieve economy by selecting appropriate concrete

ingredients.

iv. To maintain workability of concrete mix throughout work.

v. To obtain maximum possible yield per bag of cement.



Que5 List the factors affecting concrete mix design.

Ans : Factors affecting concrete mix design:

i. Water-Cement ratio

ii. Cement content

iii. Grading of aggregates

iv. Consistency

v. Admixtures

vi. Strength requirement

vii. Field or site weather conditions

Que6 Define segregation and bleeding of concrete. List any one factor

which affect above properties.

Ans: Segregation: It is defined as the separation of constituents of

concrete from each other.

Bleeding: It is a particular type of segregation in which water

comes out to the top surface of concrete.

Factors affecting segregation and bleeding :

i. Inaccurate water cement ratio

ii. Improper mixing

iii. More height of concrete placing

iv. Excessive or over vibration

Que7 Define workability and explain any 3 factors affecting workability

of concrete.

Ans: Workability – It is the easiness in handling of concrete mixture for

its mixing, transportation, placing and compaction.

Factors affecting workability –

i. Water content – If water content i.e. water-cement ratio

is more then, concrete shows more workability.

ii. Size of aggregate – if aggregate of large i.e. coarser size

is more, then concrete shows lesser workability.



iii. Shape of aggregate – If aggregate of rounded shape is

more, then concrete gives more workability.

iv. Use of admixtures – If air entraining admixtures are used,

concrete results more workability.

v. Grading – Well graded aggregate gives more workability

than poorly graded aggregate.

vi. Surface texture – Aggregate having smooth surface

texture give more workability than aggregate having

rough surface texture.

vii. Porosity and absorption of aggregate – Porous

aggregate absorb water of concrete mix and water

cement ratio decreases, workability of concrete

decreases.

viii. Temperature – As temperature increases, workability

decreases.

Que8 Define workability and list four factors affecting workability.

Ans: Workability: It is the ability of concrete for its easy handling in

various concreting operations viz. Mixing, transportation, placing

and compacting.

Factors affecting workability :

i. Water content (W/C ratio)

ii. Mix proportions of concrete

iii. Size of aggregate

iv. Shape of aggregate

v. Surface texture of aggregate

vi. Grading of aggregate

vii. Use of admixtures



Que9 Enlist two advantages of NDT and list four methods of NDT.

Ans: Advantages of NDT :

i. The strength can be tested without physical breaking of

concrete; hence it is safe.

ii. It can give internal flaws, cavities and homogeneity

details of concrete within short period.

iii. It avoids wastage of concrete, hence becomes

economical up to certain extent.

iv. It is applicable in any type and position of concrete

members shows wide applicability.

v. Its results are simple and easy to interpret.

Methods of NDT :

vi. Surface hardness test using pistol and impact hammers

vii. Rebound test using rebound hammer

viii. Penetration and pullout technique using spit pin and

Windsor probe

ix. Dynamic or vibration test using ultrasonic pulse velocity

x. Radioactive and nuclear method using X-ray and

Gamma ray

xi. Magnetic and electrical method using microwave

absorption

xii. Acoustic emission technique

Que10 Explain in detail ultrasonic pulse velocity test.

Ans: It is simple and quick test in which pulse velocity is determined

passing through concrete.

i. The ultrasonic pulse or waves are generated from pulse

generator.

ii. These waves transmit through transmitter end into the

concrete mass and receive at receiver end as shown in

fig. 3.



iii. The digital display shows the time required to pass the

waves through concrete mass.

iv. The pulse velocity is then calculated by dividing path or

wavelength by time of travel.

v. The average pulse velocity of wave propagation is

calculated by testing concrete at two more locations.

vi. Depending on pulse velocity, quality of concrete is

decided;

Que11 State the working of rebound hammer and list two limitation of it.

Ans: Working of rebound hammer:

i. It consists of spring control hammer that slides on a plunger

within a tubular housing.

ii. When the plunger is pressed against the surface of concrete,

the mass is rebound from the plunger.

iii. The hammer impacts against the concrete and the spring

control mass rebound, taking the rider along with the guide

scale.



iv. By pushing a button the rider can be held in position to allow

the reading to be taken. The distance travelled by the mass is

called rebound hammer.

v. The test can be conducted horizontally, vertically, upwards or

downward or at any intermediate angle.

Limitations of Rebound hammer test

i. The results depend upon type of cement, coarse aggregates

and their sizes.

ii. It also depends upon age of specimen and moisture condition

of the concrete

Que12 State two advantages and two disadvantages of rebound hammer test.

Ans: Advantages of rebound hammer test;

i. It is easy to operate within short duration.

ii. The results of rebound number are easy to interpret.

iii. Rebound hammer can be used horizontally, vertically

and in inclined position.

Disadvantages of rebound hammer test;

i. Rebound of hammer may get affected due to roughness

of concrete surface.

ii. The age of concrete also varies with rebound number i.e.

cured concrete gives more rebound no. than fresh one.

iii. Surface moisture of concrete may give inaccurate

rebound number

Que13 Give four advantages of RMC & two uses of it.

Ans: Advantages of RMC:

i. RMC can be ordered in bulk amount at a time.

ii. It has more homogeneity as compared to other concrete.

iii. It becomes economical in large projects.

iv. It can be easily transported at a longer distance without

hardening.



RMC are used for following purposes:

i. RMC is very useful in highly congested urban areas, where

space for mixing is unavailable.

ii. RMC helps to increase speed for construction in high rise

building.

iii. It also suits the requirements of mass concreting works like

dams, bridges, roads, etc.

iv. It is prepared in computerized machine plant, hence it is

useful to reduce labour requirement up to some extent

Que14 State two advantages and two limitations of RMC.

Ans: Advantages of Ready Mix Concrete (RMC);

i. Bulk amount of concrete can be produced at a time to

avoid delay in construction.

ii. Wastage of materials can be avoided due to

mechanized operations at plants.

iii. RMC give higher quality mix than ordinary concrete due

to computerized working of plant.

iv. It can be easily transported longer distance without

hardening, hence suitable even in congested urban

area.

Limitations of Ready Mix Concrete (RMC);

i. RMC is expensive than ordinary concrete, hence suitable

for large projects only.

ii. Continuous and bulk supply of materials is necessary for

smooth working of RMC plant.

iii. It may get affected on its quality due to improper

functioning of plant elements.

iv. It requires skilled labours for operation and it has low profit

margin.



Que15 List effect of hot weather on concrete.

Ans: Effect of hot weather on concrete

i. Accelerated settings

ii. Reduction in strength

iii. Increase tendency to cracking

iv. Rapid evaporation during curing

v. Difficulty controlling the air content

Que16 Enlist any 4 effects of hot weather on concrete.

Ans:

i. Due to hot weather, concrete shows rapid rate of

hardening, which results difficulty in transportation of

concrete.

ii. Water from concrete mix gets evaporated fastly, which

results on w/c ratio and less workability of concrete.

iii. Water may get absorbed by formwork, aggregate or

ground due to excessive heat.

iv. More shrinkage cracks get developed on concrete

surface due to incomplete hydration with less water in

concrete. Hence, early finishing becomes more essential.

v. Continuous curing is required to keep humidity and to

avoid further development of cracks.

vi. Air entrained in concrete may get expelled due to

temperature, hence workability may reduce additionally.

Que17 Enlist any 4 precautions to be taken during cold weather

concreting.

Ans: Precautions to be taken during cold weather concreting are as

follows;

i. Concrete work should be done during day time or on

sunny days.



ii. Warm water should be added for mixing of ingredients of

concrete.

iii. Before placing of concrete, the formed ice, snow or frost

should be removed from formwork.

iv. The accelerating admixtures should be used to increase

hardening of concrete.

v. A protective cover should be used over casted concrete

to avoid cold winds and snow fall.

vi. Aggregates (fine and coarse) should be heated before

its use.

Que18 List four types of special concrete & explain in brief about Self

Compacting Concrete.

Ans: Types of special concrete:

i. Ready mix concrete

ii. Reinforced concrete

iii. Prestressed concrete

iv. Light-weight concrete

v. Fiber reinforced concrete

vi. Precast concrete

vii. High performance concrete

viii. Polymer concrete

Que19 Self compacting Concrete:

Ans: Self compacting concrete is defined as the concrete which gets

leveled under its own weight without any external vibration.

It can be prepared by using suitable mineral admixture like flyash,

silica fume and chemical admixtures like accelerators, super

plasticizers, etc.

It was first invented by Prof. Okamura in Japan (1988). It has wider

applications in highly reinforced sections, thinner sections where

ordinary compaction is not possible.



Que20 What do you mean by fiber reinforced concrete and light weight

concrete?

Ans: Fiber reinforced concrete: It is a modern type of concrete & its

main action is to transfer load uniformly through the matrix of the

concrete so that micro-cracks are avoided.

The micro-cracks lead to formation of failure plains or weaker

plains within the body of concrete.

Light weight concrete: When the concrete is having bulk density

between 3KN/m3 to 18 KN/m3 then it is termed as light weight

concrete.

It is made from binding materials, steel, aggregates, water etc.

Que21 What is fibre reinforced concrete? Write any 2 applications of it.

Ans: When concrete mixture is prepared by adding individual or

combination of different types of fibres in it, then such formed

concrete is termed as Fibre Reinforced Concrete (FRC).

The fibre types like asbestos, glass, plastic, steel fibres can be

used as reinforcement in concrete to increase various strength

characteristics.

Application of FRC –

i. Machine foundations – To resist shock and dynamic

loading.

ii. Canal lining and precast elements – To gain

impermeable finish.

iii. Refractory lining – To resist temperature stresses.

Que22 Write short note on light weight concrete.

Ans: The concrete whose self-weight is lesser comparative to ordinary

concrete by using light weight aggregates (LWA).

The variety of LWA are the natural materials like volcanic pumice,

thermal treatment materials like clay, slate or shale, industrial by-

product containing fly-ash, slag etc.



The properties of light weight concrete depend on the properties of

light weight aggregates used. If high thermal insulation is required, light

and weak aggregates can be used but it results in low strength to

concrete.

Light weight concrete has following advantages;

i. Reduction in dead load gives saving in cost foundation

and reinforcement.

ii. More thermal and fire resistance.

iii. Reduction in transportation and handling cost of precast

unit.

iv. Reduction in formwork and propping

Que23 Describe the slump cone test with sketch.

Ans: Test Procedure:

i. Clean the mould from inside

ii. Place the mould on smooth horizontal, rigid & non-absorbent

surface or the centre of metallic tray.

iii. Fill the mould with the concrete to be tested in four layers,

tamping each layer 25 times with the tamping rod, taking

care that the strokes are evenly distributed over the c/s.

iv. Remove the mould by one smooth continuous vertical motion.

v. The concrete subsides & this subsidence is called “slump.”

Measure the slump in mm by using a metric scale.



Que24 State different methods of mix design and explain any one in detail.

Ans: Methods of mix design are as follows;

i. Indian Standard Method

ii. Arbitrary proportions method

iii. Maximum density of aggregate method

iv. Fineness modulus method

v. American Concrete Institute method

vi. Indian Road Congress 44 method

vii. High strength concrete mix design method

viii. Flexural strength method

ix. Surface area of aggregate method

x. Trial and error method

Indian Standard (IS 10262 – 2009) Method –

This method is suitable to design concrete of grades more than

20 N/mm2. The basic steps in design procedure are as follows;

i. Target mean strength

ii. Selection of water-cement ratio from graph as per IS 456

– 2000.

iii. Selection of water content and fine to total aggregate

ratio.

iv. Calculation of cement content per m3 of concrete.

v. Calculation of fine and coarse aggregate content per

m3 of concrete

Que25 Explain the procedure for determining of compressive strength of

concrete cubes.

Ans:

i. Take three cubes of 15 cm sides and apply oil to its inner

surface.

ii. Prepare the concrete mixture of required grade and fill it

in each mould in 3 layers. Compact each layer 25 times

with 16 mm dia. steel rod.



iii. Keep all the moulds at room temperature for 24 hrs for

initial hardening and at relative humidity 90%.

iv. Remove cube moulds and keep concrete cubes under

fresh water for curing for 7, 14, 21, 28 days.

v. Remove cube from water after curing period and keep it

under compression testing machine (CTM) for testing.

vi. Apply load at a rate of 35 N/mm2/min for 10 minutes or till

failure load in N by cross sectional area of cube in mm2.

vii. Finally calculate compressive strength of cubes as failure

load in N by cross sectional area of cube in mm2.

viii. The average of three test cubes can be calculated as

average compressive strength in MPa.

Que26 Differentiate between weight batching and volume batching.

Weight batching Volume batching

In this, measurement of

materials is done by taking

weight.

In this, measurement of

materials is done by taking

volume.

Weight machine is used. Gauge boxes are used.

It is more accurate. It is approximate or less

accurate.

It is used for more important

construction work where

mixed design is used.

It is used for less important

construction work where

ordinary mixed is used.

Weigh batching is done

generally for cement.

Volume batching is done for

aggregate and water.

It required skilled labours and

more time is required.

It require less time even with

unskilled labours.

Department of Civil Engineering

Sanjay Ghodawat Polytechnic, Atigre Page 1

For Details contact:

Mr. V.S. kumbhar

HOD

Civil Department,

Sanjay Ghodawat Polytechnic, Atigre.

Mob. No.: 7798306363

Ph. No.: 0230 -246312

Email ID: [email protected]

mailto:[email protected]

ty civil fifth semester · concept of size, specific gravity, bulk density, water absorption and...

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