UNIT-I
CONCRETE MAKING MATERIALS
1. What is meant by Surkhi?
Surkhi is fine powdered under burnt bricks. It is also known as artificial pozzolona
2. Define hydration of cement?
Cement in dry state has no bonding property. When mixed with water react Chemically and becomes
a bonding agent. These reactions are called hydration.
3. 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.
4. What are pozzolonas?
These are siliceous materials which, while having no cementations values within themselves, will
chemically react with calcium hydroxide at ordinary temperature and in the presence of moisture to
form compounds possessing cementitious properties.
5. Name any 2 natural pozzolonas.
Clay and shales, opalinc cherts, diatomaceous earth, volcanic tuffs and pumicites.
6. Name any 2 artificial pozzolonas.
Surkhi, fly ash, blast furnace slag, silica fume, rice husk ash, metakaoline.
7. 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.
8. 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.
9. 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.
10. 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.
11. What are the constituents of ordinary cement?
Alumina or clay, silica, lime, iron oxide, magnesia, sulphur trioxide, Alkalies, calcium sulphate
(gypsum).
12. What are the harmful constituents of cement?
Alkalies which are oxides of potassium and sodium, and magnesium oxide are the harmful
constituents of cement.
13. What are ball mills?
Ball mills are used for grinding the clinkers. The ball mills consist of 2 to 2.5m diameter steel
cylinder. The clinkers to be ground are fed into the cylinder and the cylinder is rotated about its
horizontal axis to carry out the grinding action.
14. What are the types of cement?
Ordinary Portland cement, rapid hardening cement, low heat cement, blast furnace slag cement,
sulphate resistant cement, air entraining cement, white and coloured cement, high alumina cement,
pozzolanic cement, super sulphate cement, expansive cement, quick setting cement, water repellant
cement, water proofing cement.
15. What are the 2 methods of manufacture of cement
Dry process
Wet process
16. Define mortar.
The mortar is a paste like substance prepared by adding required amount of water to a dry mixture of
sand or fine aggregate with some binding material like clay, lime or cement.
17. Define lime mortar.
If lime is used as a binding material, the resulting mortar is known as lime mortar.
18. Define mud mortar.
When clay is used as a binding material, the resulting mortar is known as mud mortar
19. What is known as bulking of sand?
Bulking of sand means increase in its volume. Fine aggregates or sands, increase in volume when they
possess some moisture. Bulking is due to formation of a thin film of water around the fine aggregate
or sand particles. Thickness of water film goes on increasing with more and more moisture and
consequently increase in volume continues. But after certain percentage of water, volume of sand
starts decreasing with increasing amount of water. At certain percentage of water, increase in volume
completely vanishes and volume occupied by sand becomes equal to the volume of dry sand.
20. What are the types of mortars?
Mud mortar
Lime mortar
Gauged mortar
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, water-cement ratio,
handling, placing, and other characteristics of the mix.
22. What are the methods of proportioning of concrete mixes?
Arbitrary standard method
Minimum voids method
Fineness Modulus method
Maximum density method
23. Define Abram’s water cement law.
According to Abram’s water cement law, the strength of concrete depends on the water cement ratio
used.
24. Define bleeding.
The tendency of water to rise to the surface of freshly laid concrete is known as bleeding.
25. Define laitance.
Water rising to the surface during bleeding carries with it, particles of sand and cement,which on
hardening form a scum layer known as laitance.
26. 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.
27. Define Segregation.
The tendency of separation of coarse aggregate grains from the concrete mass is called segregation.
28. What are the methods adopted to avoid segregations of concrete.
Addition of little air entraining agents in the mix.
Restricting the amount of water to the smallest possible amount.
Concrete should not be allowed to fall from larger heights.
29. 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.
30. 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 aggregates
Method of compaction of concrete
31. 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
32. Define mixing of concrete.
The process of mixing cement, water, fine aggregate and coarse aggregate in suitable proportion is
known as mixing of concrete.
33. What are the methods of consolidation or compaction of concrete?
Hand compaction
Machine compaction – i) Internal vibrators
ii) Form vibrators
iii) Surface vibrators
34. Define curing of concrete.
Curing is the operation by which moist conditions are maintained on finished concrete surface, to
promote continued hydration of cement.
35. 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.
36. Name the types of joints in concrete.
1.Construction joints
2. Expansion joints
3.Contraction joints
4. Working joints
37. What are the types of concrete used?
Plum concrete, light weight concrete, air-entrained concrete, no-fines concrete, vaccum concrete,
water-proof concrete, reinforced cement concrete, pre-stressed concrete, cellular or aerated concrete,
foamed concrete, pre-cast concrete.
38. Mention the test adopted to test the properties of cement in laboratories?
a. Fineness
b. Consistency test
c. Setting time
d. Soundness
e. Compressive strength
39. Mention the test adopted to test the properties of cement in field?
a. Open the bag and take a good look at the cement, there should not be any visible lumps
b. Thrust your hand into the cement bag should feel cool feeling
c. Take a pinch of cement and feel between the fingers. It should give a smooth feeling not
a gritty feeling
d. Take a hand full of cement and throw it on a bucket full of water, the particle should
float for sometime before they sink.
40. Mention the test adopted to test the quality of water?
a. Determination of acids and alkalis
b. Determination of total solids.
UNIT-II
CONCRETE
1. 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.
2. Define chemical admixtures
Chemicals mixed with concrete ingredients and spread throughout the body of concrete to favorably
modify the molding and setting properties of concrete mix known as chemical admixtures.
3. Define Mineral admixtures
It is a siliceous materials used to strengthen the durability properties that is classified as pozzolanic or
cementitious materials. It acts as by-product agent. E.g.: fly ash
4. What is accelerators?
Accelerators reduce the setting time and produce early removal of forms and speed up hardening. The
common accelerators are cacl 2, Al 2 cl, Nacl, Na 2 SO 4 .
5. What is the purpose of retarders?
Retarders increases the setting time of concrete mix and reduce the water cement ratio. Up to 10%
water reduction is achieved.
6. Define plasticizers
Plasticizers are defined as chemical admixtures added to wet concrete mix to impart adequate
workability properties.
7. Mention the types of plasticizers
a. Finely divided minerals
b. Air entraining agents
c. Synthetic derivatives
8. Define superplasticizers
Superplasticizers produce extreme workability and achieve reduction of water content without loss of
water cement ratio i.e workability.
9. Mention few mineral admixtures.
a. Fly ash
b. Silica fume
c. Rice husk ash
d. Metakaoline
e. GGBFS
10. What are the various admixtures used other than chemical and mineral admixtures/
a. Gas forming and expansive chemicals
b. Pigments
c. Antifungal admixtures
d. Curing compounds
e. Sealants
f. Flooring
g. Guniting aids.
11. Name the admixtures available in India?
a. Plasticizers
(a) Conplast P211- Water reducing plasticizers
(b) Conplast P509- Water reducing plasticizers/High performance plasticizers
b. Super Plasticizers
i. Conplast SP337- High workability aid
ii. Conplast SP430- High range water reducer
UNIT-III
MIX DESIGN
1. 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.
2. What is the principle of mix proportioning
a. Environmental exposure conditions
b. Grades of concrete
c. Type of cement
d. Type and size of aggregates
e. Nominal maximum size of aggregates
f. Maximum and minimum cement content
g. Maximum free water cement ratio by weight
h. Degree of workability
i. Air entrained agent
j. Types of admixtures used if any
k. Maximum/ minimum density of concrete
l. Maximum/ minimum temperature of fresh concrete
m. Type of curing and mixing
n. Source of water
3. Mention the properties related to mix design
a. Durability
b. Workability
c. Strength
d. High strength concrete
4. Describe the physical properties of materials required to mix design
a. Cement
b. Aggregate
c. Water
d. Admixtures
5. Define Nominal mix
Nominal mix is permitted by IS456:2000 for concrete of strength lower than M 25
6. Define Design mix
Design mix is permitted by IS 10262-1982 and IS456:2000 for concrete of strength Greater
than M 25 is design mix.
7. List out the advantages of Design mix
a. Properties of all materials are used.
b. Cement content is low and hence the mix design is economical.
8. List out the disadvantages of nominal mix
a. Nominal mix does not say which type of sand, cement, aggregate to be used.
b. High cement is required which leads to high cost.
9. What is ACI
American concrete institute was revised to include the use of entrained air.
10. What are the data used for ACI
a. Fineness modulus
b. Unit weight of dry rodded coarse aggregate
c. Specific gravity of cement, coarse and fine aggregate
d. Absorption characteristic of coarse and fine aggregate
UNIT-IV
SPECIAL CONCRETE
1. What is the density of concrete?
The density of concrete varies between 2200 t0 2600 kg/m3
2. Define light weight concrete.
The concrete is said to be light weight concrete whose density is between 300 to 1850 kg/m3
3. Define High density concrete
The concrete is said to be High density concrete whose density is between 3360 to 3840 kg/m3
4. Name some of the natural light weight aggregate
a. Pumice
b. Diatiomite
c. Scoria
d. Volcanic cinders
e. Saw dust
f. Rice husk
5. Name some of the artificial light weight aggregate
a. Brick bat
b. Foamed slag
c. Cinder, clinker
d. Bloated clay
e. Sintered fly ash
f. Exfoliated vermiculite
g. Expanded perlite
6. Where does high density concrete is applicable.
High density concrete is used as radiation shielding agent and it has satisfactory mechanical property
7. Mention the applications of sulphur infiltrated concrete
a. Pre cast industry
b. Fencing post
c. Sewer pipes
d. Railway sleepers
8. Define Guniting or Shotcrete?
It is defined as a mortar conveyed through a hose and pneumatically projected at a high
velocity on to a surface.
UNIT-V
CONCRETING METHODS
1. Define workability.
Workability is the 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.
2. List out the requirements of fresh concrete.
a. Mixability
b. Stability
c. Mobility
d. Compactability
e. Finishability
3. List out the Factors affecting Workability?
a. Water content
b. Mix proportion
c. Size of aggregate
d. Shape of aggregate
e. Surface texture
f. Grading
g. Admixture
4. Mention the methods to measure the workability?
a. Slump Test
b. Compaction Factor
c. Vee-Bee Consistometer
d. Kelly Ball Penetration test
e. Flow table Test
f. Vibrating table
5. Mention the values of different type of slump.
• True slump - up to 125mm from top
• Shear slump - up to 150 mm from top
• Collapse slump -150-225mm
6. List out the usage of slump values
• slump 0 – 25 mm are used in road making
• 10 – 40 mm are used for foundations with light reinforcement
• 50 - 90 for normal reinforced concrete placed with vibration
7. 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.
8. Define Vee bee consistometer
Consistometer is based on consistency test which is a mechanical variation of the simple slump test
which includes determination of the workability of concrete.Measures consistency of concrete in
terms of time required to transform by vibration a frustum of fresh concrete sample into a cylinder.
This time is called VB time.
9. What is the use of Kelly Ball Penetration test
Kelly Ball Penetration method is used to determine the penetration of a hemispherical metal weight
into freshly mixed concrete, which is related to the workability of the concrete.
10. What is the use of flow table method
Flow table indicates consistency and proneness to segregation. It is used for aggregate of size
<40mm. The flow is determined by = {D-250/250}*100.
11. What is batching.
Batching is the correct measurement of various materials used in the concrete mix. It can be either
volume or by weight.
12. How is weight batching is obtained
Weight batching is more accurate and hence preferred weighing can be done by
a. Simple spring balance
b. Platform weighing machines
c. Automatic weighing machines
13. How is mixing operation is done in concrete
a. Hand
b. Machine
a) Tilting type
1. Charging by hand
2. Charging by machine
b)Non tilting type
1. Continuous mixer
2. Pan mixer
3. Truck mixer
14. What is the purpose of compaction?
Compaction is done to eliminate air voids in concrete.
15. 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
a. Water cement ratio
b. Degree of compaction
c. Age of concrete
d. Richness of mix
e. Curing of concrete
f. Temperature of concrete.
16. Define curing
a. Curing is done to keep the concrete saturated until the water filled space in concrete is filled up by
the product of hydration.
b. Curing is done to prevent the loss of water by evaporation and to maintain the process of
hydration.
17. 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, settlement of fresh concrete is
shrinkage.
18. 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.
19. Mention the test conducted to test the properties of hardened concrete.
a. Compression Testing Machine
b. Flexure Strength Testing Machine
c. Lateral Extensometer
d. Split Tensile Test
e. Shear strength
f. Bond strength
20. List out the factors affecting the results of strength test.
a. Size and shape of aggregate
b. Condition of casting
c. Moisture condition
d. Bearing condition
e. Rate of loading
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