Concrete gains strength due to
Chemical reaction of cement with sand and coarse aggregates
Evaporation of water from concrete
Hydration of cement
All the above
Correct Answer :
C. Hydration of cement
Related Questions
Select the incorrect statement
The loss of pre-stress is more in pre-tensioning system than in posttensioning system.
Pre-tensioning system has greater certainty about its durability.
For heavy loads and large spans in buildings or bridges, posttensioning system is cheaper than pre-tensioning system
None of the above
Under normal conditions using an ordinary cement, the period of removal of the form work, is:
7 days for beam soffits
14 days for bottom slabs of spans 4.6 m and more
21 days for bottom beams over 6 m spans
All the above
For a concrete mix 1:3:6 and water cement ratio 0.6 both by weight, the quantity of water required per bag, is
10 kg
12 kg
14 kg
16 kg
The commonly used material in the manufacture of cement is
Sand stone
Slate
Lime stone
Graphite
The limits of percentage p of the longitudinal reinforcement in a column is given by
0.15% to 2%
0.8% to 4%
0.8% to 6%
0.8% to 8%
According to IS: 4561978, the flexural strength of concrete is
Directly proportional to compressive strength
Inversely proportional to compressive strength
Directly proportional to square root of compressive strength
Inversely proportional to square root of compressive strength
The following proportion of the ingredients of concrete mix, is not in conformation to arbitrary method of proportioning
1 : 1 : 2
1 : 2 : 4
1 : 3 : 6
1 : 4 : 10
For a reinforced concrete section, the shape of shear stress diagram is
Wholly parabolic
Wholly rectangular
Parabolic above neutral axis and rectangular below neutral axis
Rectangular above neutral axis and parabolic below neutral axis
Too wet concrete may cause
Weakness of concrete
Excessive laitance
Segregation
All the above
The specifications of a cement bag for storage, are
Weight 50 kg
Height 18 cm
Plan area 3000 sq. cm
All the above
For the design of retaining walls, the minimum factor of safety against overturning is taken as
1.5
2.0
2.5
3.0
Tricalcium aluminate (C3A)
Reacts fast with water
Generates less heat of hydration
Causes initial setting and early strength of cement
Does not contribute to develop ultimate strength
The entrained air in concrete
Increases workability
Decreases workability
Decreases resistance to weathering
Increases strength
Pick up the correct statement from the following:
Cement should be mixed for at least one minute
10% of water is placed in the rotating drum before adding dry material
10% of water is added after placing the other ingredients in the drum
All the above
The compaction of concrete, improves
Density
Strength
Durability
All the above
If 1500 g of water is required to have a cement paste 1875 g of normal consistency, the percentage of water is,
20 %
25 %
30 %
35 %
Efflorescence in cement is caused due to an excess of
Alumina
Iron oxide
Silica
Alkalis
The main reinforcement in the toe of a T-shaped R C. retaining wall is provided on
(i) Top face parallel to the wall
(ii) Top face perpendicular to the wall
(iii) Bottom face parallel to the wall
(iv) Bottom face perpendicular to the wall The correct answer is
Only (ii) is correct
(i) and (ii) are correct
(iii) and (iv) are correct
Only (iv) is correct
Construction joints are provided
Where B.M. and S.F. are small
Where the member is supported by other member
At 18 m apart in huge structures
All the above
Diagonal tension in a beam
Is maximum at neutral axis
Decreases below the neutral axis and increases above the neutral axis
Increases below the neutral axis and decreases above the neutral axis
Remains same
Concrete mainly consists of
Cement
Aggregates
Water
All the above
The ratio of various ingredients (cement, sand, aggregates) in concrete of grade M 200, is
1 : 2 : 4
1 : 3 : 6
1 : 1 ½ : 3
1 : 1 : 2
Grading of sand causes great variation in
Workability of concrete
Strength of concrete
Durability of concrete
All the above
Allowable shear strength of concrete, depends upon
Shear strength
Tensile strength
Compressive strength
None of these
The maximum amount of dust which may be permitted in aggregates is
5% of the total aggregates for low workability with a coarse grading
10% of the total aggregates for low workability with a fine grading
20% of the total aggregates for a mix having high workability with fine grading
All the above
The minimum diameter of longitudinal bars in a column is
6 mm
8 mm
12 mm
16 mm
The minimum cover to the ties or spirals should not be less than
15 mm
20 mm
25 mm
50 mm
Transport of concrete by pumps, is done for a distance of
100 m
200 m
300 m
400 m
The light weight aggregates are obtained from
Sedimentary rocks
Metamorphic rocks
Igneous rocks
Volcanic source
Pick up the correct statement from the following:
Lime in excess, causes the cement to expand and disintegrate
Silica in excess, causes the cement to set slowly
Alumina in excess, reduces the strength of the cement
All the above