CMT MODULE 5-6

Question 1

is a building material which solidifies and hardens after mixing
with water and placement due to chemical process known as hydration.
The water reacts with cement, which bonds the other components fine
aggregates (sand) and coarse aggregates (gravel) together; and eventually
produces a hard stone-like material.

Answer 1

Concrete

Question 2

is used to make pavements, pipe, engineering structures,
foundations, roads, bridges, walls, footings, etc.

Answer 2

Concrete

Question 3

A structural concrete with no reinforcement or with less
reinforcement than the minimum amount specified for reinforced
concrete.

Answer 3

Plain Concrete.

Question 4

A structural concrete reinforced with no less than the minimum amounts of reinforcing bars, pre-stressing tendons or non-
pre-stressed reinforcement.

Answer 4

Reinforced Concrete.

Question 5

A rich concrete mixture that can be used for columns of
reinforced concrete building and for construction where a very strong
and dense concrete is required.

Answer 5

Class AA.

Question 6

A good concrete mixture that can be used for reinforced
concrete works of all kinds and best suited for general concrete works.

Answer 6

Class A.

Question 7

A medium concrete mixture that can be used for plain concrete
foundations, walls, floors, etc. and for not much strength of
impermeability is required.

Answer 7

Class B.

Question 8

A lean concrete mixture that can be used for heavy masses.

Answer 8

Class C.

Question 9

The main ingredient is slaked lime and used as a binding
material.

Answer 9

Lime Concrete.

Question 10

Produced to suit a variety of special requirements
of environmental condition.

Answer 10

Special Cement Concrete.

Question 11

Obtained by embedding steel bars in tension
zones of the structural member to offset tension weakness of plain cement
concrete.

Answer 11

Reinforced Cement Concrete.

Question 12

Obtained with high graded steel wires or
tendon wires.

Answer 12

Pre-Stressed Cement Concrete.

Question 13

Manufactured from calcareous and siliceous materials.

Answer 13

Aerated Concrete.

Question 14

Produced by using special heavy weight
aggregates and compacting well by mechanical means.

Answer 14

Heavy Weight Concrete.

Question 15

Obtained by injecting cement sand mortar under
pressure to fill voids already packed and fully compact coarse aggregates.

Answer 15

Pre - packed Concrete.

Question 16

Contains billions of microscopic cells per ft3 and
produced by the use of air entraining Portland cement.

Answer 16

Air Entrained Concrete.

Question 17

Produced by using high-early strength cement.

Answer 17

High-Early Strength Concrete.

Question 18

Made from light weight aggregates.

Answer 18

Light weight Concrete.

Question 19

Fairly simple and quick for estimating mix proportion using
an assumed or known weight of concrete per unit volume.

Answer 19

Weight Method.

Question 20

More accurate method involves used of specific
gravity values for all ingredients to calculate the absolute volume and each
will occupy in a unit volumes of concrete.

Answer 20

Absolute-Volume Method.

Question 21

The term fineness modulus is used to indicate
an index number which is roughly proportional to the average size of the
particle in the entire quantity of aggregates.

Answer 21

Fineness Modulus Method.

Question 22

Ratio of fine aggregates and coarse aggregates
to develop a dense mix that lies between 1:1/2 and 1:2 1/2.

Answer 22

Arbitrary Standard Method.

Question 23

The quantity of fine aggregate used in the mixed
is about 10% more than the voids in the coarse aggregates and the quantity
of cement is kept about 15% more than the voids in the fine aggregates.

Answer 23

Minimum Voids Method.

Question 24

In this method a box of fixed volume
is filled with varying proportion of fine and coarse aggregates.

Answer 24

Maximum Density Method.

Question 25

The amount of water in mixing concrete is the most important factor affecting the strength of a given proportion.

Answer 25

Water Cement Ratio.

Question 26

Properties of concrete are divided into two parts:

Answer 26

Properties of Fresh Concrete or Plastic Stage and Properties of Hardened Concrete

Question 27

is a measure of the stiffness or sloppiness or fluidity of the mix. For effective handling, placing and compacting the concrete; and consistency must be the same for each batch. It is therefore necessary to measure consistency of concrete at regular intervals.

Answer 27

Consistency.

Question 28

Commonly used to measure consistency of concrete.

Answer 28

Slump Test.

Question 29

From the time of mixing, fresh concrete gradually loses consistency. This gives rise to the problems only if the concrete becomes too stiff to handle, place and compact properly. Slump loss in concrete is caused due to the following reasons: hydration of cement (generating more heat), loss of water by evaporation, absorption of water by dry aggregates and absorption of water by surfaces in contact with the concrete.

Answer 29

Slump Loss.

Question 30

The ease which concrete can be compacted fully without segregation and bleeding. The workability of a concrete mix is the relative ease with which concrete can be placed, compacted and finished without separation or segregation of the individual materials. Workability is not the same thing as consistency. Mixes with the same consistency can have different workability’s, if they are made with different sizes of stone; the smaller the stone the more workable the concrete. It is not possible to measure workability but the slump test, together with an assessment of properties like stone content, cohesiveness and plasticity; it gives a useful indication.

Answer 30

Workability.

Question 31

Implies the separation of the coarser particles from the mix which results in non-homogeneity of the concrete mix.

Answer 31

Segregation.

Question 32

The appearance of water along the cement particles on surface of freshly laid concrete on compaction and finishing.

Answer 32

Bleeding.

Question 33

Cement and aggregate particles have densities about three times that of water. In fresh concrete they consequently tend to settle and displace mixing water which migrates upward and may collect on the top

Answer 33

Settlement and Bleeding.

Question 34

The hardening of concrete before its hydration is known as setting of concrete.

Answer 34

Setting.

Question 35

Concrete derives its strength by the hydration of cement particles. The hydration of cement is not a momentary action but a process continuing for a long time.

Answer 35

Hydration.

Question 36

reduces the density of concrete and consequently reduces the strength.

Answer 36

Air entrainment.

Question 37

The characteristics strength of concrete is defined as the compressive strength of 150 mm size cubes after 28 days of curing below which not more than 5 % of the test results are expected to fail. When we refer to concrete strength; we generally talk about compressive strength of concrete. Because concrete is strong in compression but relatively weak in tension and bending.

Answer 37

Strength.

Question 38

is measured in pounds per square inch (psi) or newton per square millimeter (MPa).

Answer 38

Concrete compressive strength

Question 39

mostly depends upon the amount and type of cement used in concrete mix. It is also affected by the water-cement ratio, mixing method, placing and curing.

Answer 39

Compressive strength

Question 40

Both tensile strength and bending strength can be increased by adding reinforcement.

Answer 40

Concrete tensile strength ranges from 7% to 12% of compressive strength.

Question 41

Durability might be defined as the ability to maintain satisfactory performance over and extended service life. The design service life of most buildings is often

Answer 41

30 years

Question 41

Environmental forces such as weathering, chemical attack, heat, freezing and thawing mat deteriorate concrete. The period existence of concrete without getting adversely affected by these forces is known as

Answer 41

Durability.

Question 42

The resistance of concrete to the flow of water through its pores. Excess water during concreting leaves a large number of continuous pores leading to the permeability.

Answer 42

Impermeability.

Question 43

Concrete shrinks with age and the total shrinkage depends upon the constituents of concrete, size of the member and the environmental conditions. Total shrinkage is approximately 0.0003 of original dimension.

Answer 43

Dimensional changes.

Question 44

The volume decrease of concrete caused by drying and chemical changes. In another word, the reduction of volume for the setting and hardening of concrete is defined as shrinkage.

Answer 44

Shrinkage.

Question 45

Deformation of concrete structure under sustained load is defined as. Long term pressure or stress on concrete can make changes in shape. This deformation usually occurs in the direction the force is applied. The permanent dimension change due to loading over a long period is termed as creep.

Answer 45

Creep.

Question 46

Ec = 33 γc sqrt fc

Answer 46

Modulus of Elasticity.

Question 47

Sometimes it is called impermeability of concrete. Water tightness of concrete is directly related to the durability of concrete. The lesser the permeability; the more the durability of concrete.

Answer 47

Water Tightness.

Question 48

Concrete has moderate thermal conductivity, much lower than metals, but significantly higher than other building materials such as wood, and it is a poor insulator. A layer of concrete is frequently used for 'fireproofing' of steel structures. However, the term fireproof is inappropriate, for high temperature fires can be hot enough to induce chemical changes in concrete; which in the extreme can cause considerable structural damage to the concrete.

Answer 48

Thermal Conductivity.

Question 49

The unit weight of concrete depends on percentage of reinforcement, type of aggregate and amount of voids.

Answer 49

Unit Weight.