VETRI VINAYAHA COLLEGE OF ENGINEERING AND TECHNOLOGY

DEPARTMENT OF CIVIL ENGINEERING

Third years

CE6002 – CONCRETE TECHNOLOGY

Unit – 1

Constituent Materials

Part – A

1. What is meant by heat of hydration?

Concrete generates heat during hardening as a result of internal chemical reactions.

This heat generated is referred to as heat of hydration. The amount of heat generated depends

on various factors such as ambient temperature, w/c ratio, characteristics of cement, use of

chemical admixtures, size of structural element and surrounding environment..

2. What are the raw materials used for the production of cement?

Calcium (CaO)

Silica (SiO2)

Alumina (Al2O 3)

Iron oxide (Fe2O3)

3. What is clinker and how is it produced?

The main raw material for the production of cement is clinker. Clinker is an artificial

rock made by heating limestone and other raw materials in specific quantities to a very high

temperature in a specially made klin.

4. What are the Bouge’s chemical compound compositions of Portland cement?

Name of Compound Formula Abbreviated formula

Tricalcium silicate 3CaO.SiO2 C3S

Dicalcium silicate 2CaO.SiO2 C2S

Tricalcium aluminate 3Cao.Al2O3 C3A

Tetracalcium aluminoferrite 4CaO.Al2O3.Fe2O3 C4AF

5. State the general properties of cement.

It is an excellent building material

It attains early setting

It is easily workable

If offers good resistance to moisture

It possesses a good plasticity

6. List out the varieties of cement.

Ordinary Portland Cement (OPC)

Low Heat Cement

Oil Well Cement

Portland Pozzolana Cement

(PPC)

Portland Slag Cement (PSC)

White Cement

Low – Alkali Cement

Rapid Hardening Cement

Quick Setting Cement

High Strength Cement (HSC)

Hydrophobic Cement

7. Define setting of cement.

When water is added to cement, hydration takes place immediately as it continuous,

cement paste which is plastic becomes stiff and rigid known as setting of cement.

8. What are pozzolonas?

These are silicious materials which, while having no cementitious values within

themselves, will chemically react with calcium hydroxide at ordinary temperature and in the

presence of moisture to form compounds possessing cementitious properties

9. What is natural cement?

Natural cement is manufactured by burning and then crushing the natural cement

stones. Natural cement stones are such stones which contain 20% to 40% of argillaceous

matter i.e. clay, and remaining content mainly calcareous matter which is either calcium

carbonate alone or a mixture of calcium carbonate and magnesium carbonate.

10. What is artificial cement?

Artificial cement is manufactured by burning approximately proportioned mixture of

calcareous and argillaceous materials at a very high temperature and then grinding the

resulting burnt mixture to a fine powder.

11. What are the harmful constituents of cement?

Alkalies which are oxides of potassium and sodium and magnesium oxide are the

harmful constituents of cement.

12. What is the function of gypsum in the manufacture of cement?

In order to delay the setting action of cement, when mixed with water, a little

percentage of gypsum is added in the clinker before grinding them to fine powder.

13. What are the two methods of manufacture of cement?

Dry process

Wet process

14. What is known as clinker?

Artificial cement is manufactured by burning approximately proportioned mixture of

calcareous and argillaceous materials at a very high temperature and then grinding the

resulting burnt mixture to a fine powder. The burnt mixture of calcareous and argillaceous

matter is known as clinker.

15. Define aggregate.

Aggregates are defined as inert, granular and inorganic materials that normally

consist of stone or stone-like solids. Aggregates can be used alone (in road bases and various

types of fill) or can be used with cementing materials (such as Portland cement or asphalt

cement) to form composite materials or concrete.

16. What is the common classification of aggregates?

The most common classification of aggregates on the basis of bulk specific gravity is

lightweight, normal-weight and heavyweight aggregates.

17. What is a light weight aggregate?

Lightweight concrete contains aggregate that is natural or synthetic which weighs less

than 1100 kg/m3. The lightweight is due to the cellular or high internal porous

microstructure, which gives this type of aggregate at low bulk specific gravity. The most

important aspect of lightweight aggregate is the porosity. They have high absorption values,

which require a modified approach to concrete proportioning.

18. What are the effects of alkali aggregate reaction?

A high moisture level, within the concrete

Cement with high alkali content or another source of alkali

Aggregate containing an alkali reactive constituent

19. Define heavy weight aggregates.

Heavyweight concrete contains aggregates that are natural or synthetic which weigh

more than 2080 kg/m3 and can range up to 4485 kg/m

3. Heavyweight is most commonly used

for radiation shielding, counterweights and other applications where a high mass-to-volume

ratio is desired.

20. What are the various tests which are to be done on aggregates?

Various test which are done on aggregates are listed below

Sieve Analysis

Water Absorption

Aggregate Impact Value

Aggregate Abrasion Value

Aggregate Crushing Value

21. What is meant by grading of aggregates?

Grading of aggregate means particle size distribution of the aggregate. If all the

particle of an aggregate were of one size, more voids will be left on the aggregate mass.

Properly graded aggregate produces dense concrete and needs smaller quantities of fine

aggregate and cement.

Grading determines the workability of the mix, which controls segregation, bleeding,

w/c ratio, handling, placing and other characteristics of the mix.

22. Define fineness modulus of aggregates.

The characterize the overall coarseness or fineness of an aggregate, a concept of

fineness modulus is developed. To calculate the fineness modulus, the sum of the cumulative

percentages retained on a definitely specified set of sieves needs to be determined, and the

result is then divided by 100.

23. What are the factors affecting particle size distribution?

Workability

Mix proportioning

Freeze-thaw resistance

24. Mention the various types of gradation of aggregate.

a) Uniform grading

b) Continuous grading

c) Gap grading

25. Mention the classification of aggregate in accordance with size.

Coarse aggregate: Aggregates passing on 20 mm sieve and predominately retained

on 4.75 mm sieve.

Fine aggregate (sand): Aggregates passing on 4.75 mm sieve and predominately

retained on 75μm sieve.

26. What are the tests to be conducted to ensure the cement supplied at the site is good?

Open the bag and take a good look at the cement, there should not be any visible

lumbs.

Thrust your hand into the cement bag should feel cool feeling.

Take a pinch of cement and feel between the fingers. It should give a smooth felling

not a gritty feeling.

Take a hand full of cement and throw it on a bucket full of water, the particle should

float for sometime before they sink

.

27. Describe the importance of the quality of water used for concreting.

The quality of water used must be checked for ensuring good quality concrete. Water

used for mixing and curing should be free from oil, acid and alkali, salts and organic

material. It should be of potable quality and generally purer than that required for drinking.

28. What is the purpose of water in concrete?

It distributes the cement evenly.

It reacts with cement chemically and produces calcium silicate hydrate gel.

It provide for workability, i.e., it lubricates the mix.

29. Write the two sources of water in concrete.

Intentionally added water, known as mix water

Aggregate moisture, which can either add water to the mixture or absorb water from

the mixture.

30. Mention the test adopted to test the quality of water.

Determination of acids and alkalis

Determination of total solids

Part – B

1. Distinguish between specific surface and surface index of aggregates.

2. Explain the experimental procedure for determination of clay, fine slit and fine dust from

fine aggregate.

3. What is unsoundness in cement? What causes it and what is its effect? How is it

determined in the laboratory? Give the BIS specification for the same.

4. State and explain the various characteristics of aggregates that influence the quality of

concrete.

5. How would you conduct the aggregate crushing value and impact value test? What are

the acceptance criteria?

6. Explain in detail of any three tests for aggregates.

7. Write the procedure and specification for testing of aggregate

a) Specific gravity

b) Bulk density and Voids

8. Explain in details the field tests employed for cement to ascertain its quality.

9. Explain the following in detail:-

a) Grading of aggregate

b) Quality of water for concrete preparation

10. Explain the methods to measurement of moisture content of aggregates?

11. Explain the following types of cement highlighting. How it is different from ordinary

Portland cement?

12. Explain in details the different tests employed for cement to ascertain its quality as per IS

specification.

13. Write a note on the use of sea water for concrete preparation.

Unit – 2

Chemical and Mineral Admixtures

Part – A

1. What are the various purpose for which admixtures are used in concrete?

Some chemical are mixed with concrete ingredients and spread throughout the body

of concrete to favorably modify the moulding and setting properties of the concrete

mix. Such chemical are generally known as chemical admixtures.

Some chemicals are applied on the surface of concrete mix. Such chemical are

generally known as chemical admixtures.

Some chemicals are applied on the surface of concrete to protect it during or after its

setting.

Some chemical are applied to bond or repair broken or chipped concrete.

2. What are the uses of retarders?

Retarders increase the setting time of the concrete mix and reduced the w/c ratio.

Usually up to 10% water reduction can be achieved.

A wide range of water-reducing and set-retarding admixtures are used in ready mixed

concrete.

3. What is meant by artificial pozzolanas?

Pozzolanic materials are siliceous or siliceous and aluminous materials, which in

themselves possess little or no cementitious value, but will, in finely divided form and in the

presence of moisture, chemically react with calcium hydroxide liberated on hydration, at

ordinary temperature, to form compounds, possessing cementitious properties.

Artificial pozzolans

Fly Ash

Blast Furnace Slag

Silica Fume

Rice Husk Ash

Metakoaline

Surkhi

4. What are admixtures?

Admixtures are ingredients other than cement, fine aggregate and coarse aggregate to

improve the quality of concrete. The addition of an admixture may improve the concrete with

respect to its strength, hardness, workability, water resisting power etc.,

5. What are the types of Admixtures?

A. Chemical admixtures

Accelerators

Retarders

Water-reducing agents

Super plasticizers

Air entraining agents, etc.

B. Mineral admixtures

Fly-Ash

Silica Fume

GGBS

Rice Husk Ash

Metakaoline

6. Define chemical admixtures.

Chemicals mixed with concrete ingredients and spread throughout the body of

concrete to favourably modify the molding and setting properties of concrete mix is known

as chemical admixtures.

7. Define mineral admixtures.

It is the siliceous materials used to strengthen the durability properties that are

classified as pozzolanic or cementitious materials. It acts as by-product agent.

8. What are accelerators?

Accelerators reduce the setting time and produce early removal of forms and speed up

hardening. They are helpful in cold weather concreting. The common accelerators are CaCl2,

Al2Cl, NaCl and Na2SO4.

9. What are plasticizers?

Plasticizers for concrete increase the workability of the wet mix or reduce the water

required to achieve the desired workability and are usually not intended to affect the

properties of the final product after it hardens.

10. What are retarders?

Retarders increase the setting time of the concrete mix and reduce the w/c ratio.

Usually up to 10% water reduction can be achieved. A wide range of water-reducing and set-

retarding admixtures are used in ready mixes concrete.

11. What is the purpose of adding admixture in concrete?

To improve the strength of concrete

To accelerate the initial setting of concrete

To retard the initial set

To improve workability

To inhibit the corrosion of concrete

To increase the durability of concrete

To increase the resistance to chemical attack.

12. What is fly ash?

The fly ash or pulverized fuel ash is the residue from the combustion of pulverized

coal collected by the mechanical dust collectors or electrostatic precipitous or separators

from fuel gases of thermal power plants.

13. What is Granulated blast furnace slag?

It is a waste industrial by-product obtained during the production of iron. The blast

furnace slag is non-metallic product having oxide composition similar to that of Portland

cement clinker, it consists essentially of silicates and aluminates of calcium and other bases

but if contains lesser calcium oxide.

14. What is metakaoline?

Metakaoline is refined kaolin clay that is fired (calcined) under carefully controlled

conditions to create an amorphous aluminosilicate that is reactive in concrete. Like other

pozzolans (fly ash and silica fume are two common pozzolans), metakaolin reacts with the

calcium hydroxide (lime) by-products produced during cement hydration.

15. What is the purpose of using accelerators?

To permit earlier removal of formwork

Reduce the required period of curing

Advance the time that a structure can be placed in service

In the emergency repair work partially compensate for the retarding effect of low

temperature during cold weather concreting

16. What is silica fume?

Silica fume also called micro silica is a light to dark grey or pink or white cementing

material composed of atleast 85% ultra-fine, amorohous non-crystalline spherical silicon

dioxide particles give silica fume the super pozzolanic properties.

17. How does metakaolin boost compressive strength?

Calcium hydroxide accounts for up to 25% of the hydrated Portland cement and

calcium hydroxide does not contribute to the concrete strength or durability. Metakaolin

combines with the calcium hydroxide to produce additional cementing compounds, the

material responsible for holding concrete together. Less calcium hydroxide and more

cementing compounds means stronger concrete.

18. How does metakaolin reduce efflorescence?

Efflorescence which appears as a whitish haze on concrete is caused when calcium

hydroxide reacts with carbon dioxide in the atmosphere. Because metakaolin consumes

calcium hydroxide, it reduces efflorescence

19. How does metakaolin mitigate alkali-silica reaction?

Alkali-silica reaction is a reaction between calcium hydroxide (the alkali) and glass

(the silica) which can cause decorative glass embedment’s in concrete to pop out. Because

metakaolin consumes calcium hydroxide, it takes away the alkali and the reaction does not

occur.

20. What is Air Entrainment?

The production within the concrete mix of a large number of small bubbles of air.

Normally these bubbles are less than 1mm in diameter. The bubbles must be stable and

remain in the concrete as it is transported and placed so that they are still present in the

hardened mass of concrete. To provide freeze and thaw resistance the bubbles must be evenly

spread throughout the concrete.

Part – B

1. What is super plasticizer? What are the classifications of super plasticizers?

2. Explain the effects of super plasticizers on fresh and hardened concrete.

3. Define air entrained concrete. Explain the factors affecting of air entrainment.

4. Mention the various types of chemical admixtures that influence used. Explain the

application of any two chemical admixtures.

5. When are mineral admixtures preferred over chemical admixtures? Explain the use of

mineral admixtures bringing out their effect on the concrete properties.

6. What are the important purpose using admixtures in concrete?

7. Write short notes on Silica Fume. Explain the composition and properties of Silica Fume

and admixtures bringing out their effect on the concrete properties.

8. Write short notes on Fly Ash. Explain the composition and properties of Fly Ash and

admixtures bringing out their effect on the concrete properties.

9. Write short notes on: a) High Volume Fly Ash Concrete

b) Ground Granulated Blast Furnace slag c) Metakaolin

10. Write short notes on: a) Plasticizers b) Water Proofers

11. Write short notes on: a) Retarders b) Accelerators

Unit – 3

Proportioning of Concrete Mix

Part – A

1. What are nominal mix and design mix? Which is better? Why?

Nominal mix: it is used for relatively unimportant and simpler concrete works. In

this type of mix, all the ingredients are prescribed and their proportions are specified.

Therefore there is no scope for any deviation by the designer. Nominal mix concrete may be

used for concrete of M20 or lower.

Design mix: it is a performance based mix where choice of ingredients and

proportioning are left to the designer to be decided. The user has to specify only the

requirements of concrete in fresh as well as hardened state. The requirements in fresh

concrete are workability and finishing characteristics whereas in hardened concrete these are

mainly the compressive strength and durability.

2. Define concrete.

Concrete is obtained by mixing cementing materials, water, aggregate and sometimes

admixtures in required proportions. This mixture when placed in forms and allowed to cure

hardens into rock like mass known as concrete.

3. List out the advantages of Design mix.

Properties of all materials are used.

Cement content is low and hence the mix design is economical.

4. List out the disadvantages of nominal mix.

Nominal mix does not say which type of sand, cement, aggregate to be used.

High cement is required which leads to high cost.

5. List the various methods of proportioning of concrete mix.

Arbitrary proportion

Fineness modulus method

Maximum density method

Surface area method

Indian Road Congress, IRC 44

method

High strength concrete mix

design

Mix design based on flexural

strength

ACI committee 211 method

DOE method

Indian standard recommended

method IS:10262-2009

6. Differentiate average design strength and specified minimum strength..

In the design of concrete mixes the average design strength to be aimed at should be

appreciably higher than the minimum strength stipulated by the structural designer. The

value of average design strength to be aimed at will depend upon the quality control

exercised at the time of making concrete.

7. What is proportioning of concrete mix?

Proportioning of concrete mix is the art of obtaining a suitable ratio of the various

ingredients of concrete with the required properties at the lowest cost.

8. Define 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.

9. Define Standard mixes.

The nominal mixes of fixed cement-aggregate ratio (by volume) vary widely in

strength and may result in under or over-rich mixes. For this reason, the minimum

compressive strength has been included in many specifications. These mixes are termed

standard mixes. IS 456-2000 has designated the concrete mixes into a number of grades as

M10, M15, M20, M25, M30, M35 and M40. In this designation the letter M refers to the mix

and the number to the specified 28 days cube strength of mix in N/mm2. The mixes of grades

M10, M15, M20 and M25 correspond approximately to the mix proportions (1:3:6), (1:2:4),

(1:1.5:3), and (1:1:2) respectively.

10. What are the variable factors to be considered in connection with specifying a

concrete mix?

Water cement ratio

Cement content or cement-aggregate ratio

Gradation of the aggregates

Consistency

11. Mention the properties related to mix design.

Durability

Workability

Strength

High strength concrete

12. What is meant by statistical quality control?

The aim of quality control is to limit the variability as much as practicable. Statistical

quality control method provides a scientific approach to the concrete designer to understand

the realistic variability of the materials so as to lay down design specifications with proper

tolerance to cater for unavoidable variations. The acceptance criteria are based on statistical

evaluation of the test result of samples taken at random during execution.

13. What are the common terminologies used in the statistical quality control?

Mean strength

Variance

Standard deviation

Coefficient of variation

14. What are the steps are taken for choosing the appropriate w/c ratio?

Verify the types of cement and determine the seven-day cement strength.

Choose the corresponding w/c ratio versus strength curve.

For the required concrete strength on the Y-axis, read off the w/c ratio from the

corresponding curve.

15. What is the information required for grade of concrete?

Type of mix that is design mix or

nominal mix

Grade designation

Type of cement

Maximum nominal size of

aggregate

Minimum cement content

Maximum water-cement ratio

Workability

Mix proportion (for nominal

mix)

Exposure condition as per IS 456

Maximum temperature of

concrete at the time of placing

Method of placing

Degree of supervision

16. What are the requirements of concrete mix design?

The minimum compressive strength required from structural consideration

The adequate workability necessary for full compaction with the compacting

equipment available.

Maximum w/c ratio and/or maximum cement content to give adequate durability for

the particular site conditions.

Maximum cement content to avoid shrinkage cracking due to temperature cycle in

mass concrete.

17. Mention the types of mixes.

Nominal mixes

Standard mixes

Designed mixes

18. What are the factors affecting the choice of mix proportions?

Compressive strength

Workability

Durability

Maximum nominal size of aggregate

Grading and type of aggregate

Quality control

19. What are the factors to be considered for mix design?

The grade designation giving the characteristic strength requirement of concrete

The type of cement influences the rate of development of compressive strength of

concrete

The cement content is to be limited from shrinkage, cracking and creep.

20. What are the methods used to concrete mix design for ordinary concrete?

Arbitrary proportion

Fineness modulus method

Maximum density method

Surface area method

Indian Road Congress, IRC 44 method

High strength concrete mix design

Part – B

1. Distinguish between the term sampling and acceptance criteria in proportioning of

concrete mix.

2. Explain the factors that influence the choice of mix design.

3. Discuss inn details the Principles of mix proportioning.

4. Discuss in details the Properties of concrete related to mix design.

5. Discuss in details the Physical properties of materials required for mix design.

6. Write short notes on different types of concrete mix.

7. What are the various methods used for proportioning concrete? And explain any four

methods.

8. Write the step by step procedure of IS method of mix design.

9. Design of M20 concrete mix as per IS 10262:2009; cement – OPC, specific gravity – 3.15,

Sand – grading zone – I, Coarse aggregate – 20mm angular, Exposure condition – Mild,

Water absorption of coarse aggregate 0.6% & fine aggregate 1%, Workability – 75 mm

(slump).

10. Design of M30 concrete mix as per IS 10262:2009; cement – OPC, specific gravity – 3.15,

Sand – grading zone – II, Coarse aggregate – 20mm angular, Exposure condition –

Moderate, Water absorption of coarse aggregate 0.6% & fine aggregate 1%, Workability

– 50 mm (slump).

Unit – 4

Fresh and Hardened Properties of Concrete

Part – A

1. What is concrete slump? With example sketches show how a concrete can undergo

slump?

The concrete slump test is an empirical test that measures the workability of fresh

concrete. More specifically it measures the consistency of the concrete in that specific batch.

This test is performed to check the consistency of freshly made concrete.

2. Enumerate the factors which affect the strength of concrete.

Quality of cement and chemical

constituents

Quality of water to making water

Grade of aggregate

Degree of compaction

Curing temperature

Curing efficiency

3. Define gel/space ratio.

The gel/space ratio is the ratio of solid products of hydration to the space available for

these hydration products.

Gel is the hydrated cement while space is volume occupied by hydrated cement plus

capillary pores. Hence gel/space ratio is the fraction of volume occupied by hydrated cement

in the total space occupied by hydrated cement and capillary pores.

4. What is batching of concrete?

Batching is the process of measuring concrete mix ingredients by either mass or

volume and introducing them into the mixer. To produce concrete of uniform quality, the

ingredients must be measured accurately for each batch..

5. Define weigh batching.

Weigh batching is defined as measuring the constituent materials for mortar or

concrete by weight.

6. What is volume batching?

Volume batching is defined as the measuring of the constituent materials for mortar

or concrete by volume.

7. Define Abram’s water cement law.

According to Abram’s water cement law, the strength of concrete depends on the

w/c ratio used.

8. Define bleeding.

The tendency of water to rise to the surface of freshly laid concrete is known as

bleeding.

9. What are the steps adopted to control bleeding?

By adding more cement

By using more finely ground cement

By using little air entraining agent

By increasing finer part of fine aggregate

By properly designing the mix and using minimum quantity of water.

10. Write the factors influencing durability of concrete.

The environment

The cover to embedded steel

The type and quality of constituent materials

The cement content and w/c ratio of the concrete

Workmanship, to obtain full compaction and efficient curing

The size and shape of the member

11. Write the factors influencing consistency.

The consistency of fresh concrete depends on many factors, the main ones being:

Water content (kg/m3)

Water/cement ratio

Fineness modulus of the

aggregate

Use of water reducers

(plasticizers/super plasticizers)

Type and shape of aggregate

Entrained air content

12. Define segregation.

The tendency of separation of coarse aggregate grains from the concrete mass is

called segregation.

13. What are the methods adopted to avoid segregation of concrete?

Addition of little air entraining agents in the mix.

Restricting the amount of water to the smallest possible amount.

Concrete should be allowed to fall from larger heights.

14. Give the types of concrete mixes.

Nominal mixes

Standard mixes

Designed mixes

15. Define workability.

Workability is that property of concrete which determines the amount of internal

work necessary to produce full compaction. It is a measure with which concrete can be

handled from the mixer stage to its final fully compacted stage.

16. What are the factors affecting workability?

Quantity of water in the mix

Proper grading of the aggregate mix

Ratio of fine aggregate and coarse aggregate

Maximum size of coarse aggregate

Method of compaction of concrete

17. What are the factors affecting proportioning of concrete mixes?

Water cement ratio

Cement content

Temperature

Age of concrete

Size, shape and grading of aggregate

Curing

18. What are the tests to find the workability of concrete?

Workability of concrete can be determined by

Slump test

Compacting factor test

Flow test

Kelly ball test

Vee Bee test

19. List out the requirements of fresh concrete.

Mixability

Stability

Mobility

Compactability

Finishability

20. What are the methods adopted in compaction?

Hand compaction

- Rodding

- Ramming

- Tamping

Machine compaction

- Internal vibrator

- Formwork vibrator

- Table vibrator

- Platform vibrator

- Surface vibrator (screed vibrator)

- Vibratory roller

Compaction by pressure and jolting

Compaction by spinning

21. Define compaction factor.

Compaction factor is the ratio of the weight of partially compacted concrete to the

weight of the concrete when fully compacted in the same mould.

22. What is the purpose of compaction?

Compaction is done to eliminate air voids in concrete.

23. Define mixing of concrete.

The process of mixing cement, water, fine aggregate and coarse aggregate in suitable

proportion is known as mixing of concrete.

24. Define curing of concrete.

Curing is the operation by which moist conditions are maintained on finished

concrete surface, to promote continued hydration of cement.

25. What are the characteristics of good concrete?

It should have high compressive strength.

On hardening, it should exhibit minimum shrinkage.

It must be adequately dense. The density of a good concrete should be about 24

kN/m3.

It should be adequately durable to resist the effects of weathering agencies.

It should have minimum creep.

It should have minimum thermal expansion so as to provide good resistance to fire.

26. List out the usage of slump values.

Slump 0 – 25 mm is used in road making.

10 – 40 mm is used for foundations with light reinforcement

50 – 90 mm for normal reinforced concrete placed with vibration

27. What is hardened concrete? And mention the factors influence its strength.

Hardened concrete gives an overall idea about the quality of concrete. It depends on

Water cement ratio

Degree of compaction

Age of aggregate

Richness of mix

Curing of concrete

Temperature of concrete

28. Define curing.

Curing is done to keep the concrete saturated until the water filled space in concrete is

filled up by the product of hydration.

Curing is done to prevent the loss of water by evaporation and to maintain the process

of hydration.

29. Define shrinkage.

Volume change due to loss of moisture affects durability and strength, causes cracks

in concrete at different stage due to alkali aggregate reaction, sulphate action and settlement

of fresh concrete is shrinkage.

30. Define creep.

When a concrete member is loaded it deforms to a certain extent as soon as the load is

applied. When the load is kept constant, the deformation increases with time. This increase in

strain under sustained stress is called creep of concrete.

31. Mention the test conducted to test the properties of hardened concrete.

Compression testing machine

Flexure strength testing machine

Lateral extensometer

Split tensile test

Shear strength

Bond strength

32. List out the factors affecting the results of strength test.

Size and shape of aggregate

Condition of casting

Moisture condition

Bearing condition

Rate of loading

33. What are the factors affecting strength of hardened concrete?

The strength of hardened concrete depends on many factors, the main ones being:

W/C ratio

Strength of the cement

Type and shape of aggregate

Entrained air content

34. How to improve the workability of concrete.

Increase water/cement ratio

Increase size of aggregate

Increase the mixing time

Increase the mixing temperature

Use non-porous and saturated aggregate

With addition of air entraining mixtures.

Part – B

1. Explain the various steps involved in manufacturing of concrete.

2. Define the term workability. What are the various tests conducted to determine the

workability of concrete and explain them. (OR) Explain with neat sketch the various tests

on fresh concrete.

3. Explain the procedure of compacting factor test.

4. Explain in detail the various factors affecting workability of concrete.

5. Distinguish between segregation and bleeding of concrete.

6. Describe in details the various properties of fresh and hardened concrete.

7. With neat sketches explain the various tests on hardened concrete.

8. Explain with neat sketches the non-destructive test on concrete.

9. What is re-vibration? Is it detrimental to concrete? Where is it practiced?

10. Discuss maturity of concrete? How is it measured? What is its practical use in the

concrete industry?

11. Explain the significance of quality control.

12. How dose freeze-thaw damage occur?

Unit – 5

Special Concretes

Part – A

1. State the applications and advantages of light weight concrete.

Application

Thermal insulating and sound-proofing

Remodeling of existing buildings

Leveling of floors and paving stairs

Docks and floating platforms

Advantages

There are many advantages of having low density

Light weight concrete very economy

Low thermal conductivity

Low density

2. What do you understand by high performance concrete? How is it different from

normal concrete?

High performance concrete is used for concrete mixture which possess high

workability, high modulus of elasticity, high density, high dimensional, stability, low

permeability and resistance to chemical attack.

It may be recalled that in normal concrete, relatively low strength and elastic modulus

are the result of high heterogeneous nature of structure of the material, particularly the

porous and week transition zone, which exists at the cement paste-aggregate interface.

3. What is meant by high density concrete?

Density of normal concrete is in the order of about 2400 kg/m3. The density of light

weight concrete will be less than about density 1990 kg/m3. To call the concrete, as high

density concrete, in must have unit weight ranging from about 3360 kg/m3 to 3840 kg/m

3,

which is about 50% higher than the unit weight of conventional concrete.

4. What are the applications of sulphur-infiltrated concrete?

The sulphur-infiltrated concrete can be employed in the precast industry. This

methods of achieving high strength can be used in the manufacture if precast roofing

elements, fencing posts, sewer pipes and railway sleepers, sulphur-infiltrated concrete should

find considerable use in industrial situations, where high corrosion resistant concrete.

5. Write a short note on sulphur infiltrated concrete.

Sulphur was made to impregnate (saturate) into lean porous concrete, to improve its

strength and other useful properties considerably. In this method, the quantity of sulphur used

is also comparatively less and thereby the process is made economical. It is reported that

compressive strength of about 100 MPa could be achieved in about 2 days time.

6. What is the density of concrete?

The density of concrete varies between 2200 to 2600 kg/m3.

7. Define light weight concrete.

The concrete is said to be light weight concrete whose density is between 300 to

1850 kg/m3.

8. Define high density concrete.

The concrete is said to be high weight concrete whose density is between 3360 to

3840 kg/m3.

9. Name some of the natural light weight aggregates.

Pumice

Volcanic cinders

Saw dust

Rice husk

Diatiomite

Scoria

10. Name some of the artificial light weight aggregate.

Brick bat

Sintered fly ash

Exfoliated vermiculite

Expanded perlite

Foamed slag

Cinder and clinker

11. What are the special methods of making high strength concrete?

Seeding

Re-vibration

High speed slurry mixing

Use of admixtures

Inhibition of cracks

Sulphur impregnation

Use of cementitious aggregates

12. Why high strength concrete is used for concrete repairs?

High strength concrete for concrete repair is used to provide a concrete with

improved resistance to chemical attack, better abrasion resistance, improved resistance to

freezing and thawing and reduced permeability

13. Name the types of joints in concrete.

Construction joints

Expansion joints

Contraction joints

Warping joints

14. What are the types of concrete?

Fibre reinforced concrete (FRC)

Light weight concrete (LWC)

High performance concrete (HPC)

High strength concrete (HSC)

Ferrocement

Ready mixed concrete (RMC)

Gunite or shotcrete

Polymer concrete

Geopolymer concrete

Slurry infiltrated fibrous reinforced concrete (SIFCON)

15. What is HPC?

HPC is a concrete made with appropriate materials combined as per selected mix

design, carefully mixed, transported, placed and cured so that the resultant concrete give

excellent performance in the structure in which it is used in the environment to which it is

likely to be exposed and with the load to which it is subject to design life.

16. Mention the applications of sulphur infiltrated concrete.

Precast industry

Railway sleepers

Fencing post

Sewer pipes

17. What are the advantages of using high strength concrete?

Reduction in self weight and a consequent reduction in the foundation cost

Reduction in axial shortening effects in column

Reduction in floor thickness and beam height

Reduction in member size

Reduction in maintenance costs

Lower creep and shrinkage

18. What are the applications of polymer cement concrete?

Polymer cement concrete is made by mixing cement, aggregates, water and

monomers, such plastic mixture is cast in moulds, cured, dried and polymerized.

19. What is ready mix concrete?

Ready mix concrete has cement, aggregates, water and other ingredients which are

weighing batched at a centrally located plant. This is then delivered to the construction site in

transit mixers and can be used straight away without any further treatment.

20. What are the advantages of RMC over site mix concrete?

A centralized concrete batching plant can serve a wide area.

Better quality concrete is produced.

Elimination of storage space for basic materials at site.

Wastage of basic materials is avoided.

Time required is greatly reduced.

21. What is self-compacting concrete?

Self-compacting concrete is a non-segregating concrete that is placed by means of its

own weight. The importance of self-compacting concrete is that maintains all concrete

durability and characteristics, meeting expected performance requirements

22. What is Shotcrete?

Shotcrete is a concrete conveyed through a hose and pneumatically projected at high

velocity onto a surface, as a construction technique. Shotcrete undergoes placement and

compaction at the same time due to the force with which it is projected from the nozzle. It

can be impacted into any type or shape of surface, including vertical or overhead areas.

23. What is the general use of Shotcrete?

While most shotcrete placed is the traditional dry-mix and wet-mix shotcrete, the use

of specially shotcretes has become common. The addition of accelerators, fibers and silica

fume can provide shotcrete with significantly enhanced performance.

24. What are the different types of polymers used in concrete?

Vinyl

Urethanes

Acrylics

Styrene butadiene

Epoxies

25. Give a list of components of a typical ready mixed concrete plant.

Overhead crane

Cement weigh hopper

Pan mixer

Skip hoist winch

Service walkway

Weighing cage

Skip

Control cabin

Electro compressor

Loading screw feed

Cement silo

Aggregates partition walls

26. Define Guniting or shotcrete?

It is define as a mortar conveyed through a hose and pneumatically projected at a high

velocity on to a surface.

27. What is meant by Ferro-cement?

Ferro cement is defined as a thin-wall reinforced concrete spaced layers of continuous

and relatively small diameter mesh. The mesh may be made of a metallic or other suitable

material. Ferro cement is both a method and a material used in building or sculpture with

cement, sand, water and wire mesh material, often called the thin shell.

28. Mention some of the materials used for ferrocement.

The reinforcing wire

Wire netting

Cement

Sand

Water

Admixtures

Part – B

1. Define high performance concrete. Explain the properties and application.

2. What is meant by RMC? Explain their advantages and disadvantages.

3. What are the various fibers that are used in the manufactures of fibre reinforced concrete?

4. What is polymer concrete? What are the various types? Explain properties and

application.

5. Why is light weight concrete preferred for construction particulars in multi-storey

building? Explain with respect to their physical characteristics of light weight aggregate

concrete?

6. Describe the important fresh state properties of high strength concrete.

7. How the various quality controls is tests done to ensure good performance of polymer

concrete?

8. Give the typical layout of ready mixed concrete plant.

9. What are the special features of transportation of ready mixed concrete from the plant to

the site?

10. What special features are to be considered while handling and placing ready mixed

concrete?

11. Explain in detail the method of design of light weight concreting.

12. Describe the procedure of mass concrete.

13. Write short notes on Shotcrete.

14. Write short notes of Grouting (or) write short notes on shotcrete.

15. Explain the properties of polymer impregnated concrete.

16. Write short notes on high density concrete.

17. Explain the various methods of polymer concrete.

18. What are the advantages of using ready mixed concrete instead of site mixed concrete?