Air entrainment in the concrete increases
Workability
Strength
The effects of temperature variations
The unit weight
Correct Answer :
A. Workability
Related Questions
The grade of concrete M 150 means that compressive strength of a 15 cm cube after 28 days, is
100 kg/cm2
150 kg/cm2
200 kg/cm2
250 kg/cm2
Sands of zone I are:
Course
Medium
Medium to fine
Fine
To ensure constant moisture content in aggregates
Area of each aggregate pile should be large
Height of each aggregate pile should not exceed 1.50 m
Aggregate pile should be left for 24 hours before aggregates are used
All the above
Pick up the correct statement from the following:
A highly absorptive aggregate reduces the workability of concrete considerably
The specific gravity of aggregate is important for the determination of the moisture content
The absorption and porosity of an aggregate influence the property of the concrete
All the above
Water cement ratio is generally expressed in volume of water required per
10 kg
20 kg
30 kg
50 kg
Admixtures which cause early setting and hardening of concrete are called
Workability admixtures
Accelerators
Retarders
Air entraining agents
If the storey height is equal to length of RCC wall, the percentage increase in strength is
0
10
20
30
For the construction of R.C.C. slabs, columns, beams, walls, etc. the grade of concrete mix used, is
1 : 3 : 6
1 : 1 ½ : 3
1 : 2 : 4
1 : 1 : 2
In case of hand mixing of concrete, the extra cement to be added is
5 %
10 %
15 %
20 %
Pick up the correct statement from the following:
Continuous grading is not necessary for obtaining a minimum of air voids
The omission of a certain size of aggregate is shown by a straight horizontal line on the grading curve
The omission of a certain size of aggregate in concrete increases the workability but also increases the liability to segregation
All the above
Expansion joints are provided if the length of concrete structures exceeds
10 m
15 m
15 m
45 m
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
The effect of creep on modular ratio is
To decrease it
To increase it
Either to decrease or to increase it
To keep it unchanged
A beam curved in plan is designed for
Bending moment and shear
Bending moment and torsion
Shear and torsion
Bending moment, shear and torsion
According to IS: 4561978, minimum slenderness ratio for a short column is
Less than 12
Less than 18
Between 18 and 24
More than 24
If 50 kg of fine aggregates and 100 kg of coarse aggregates are mixed in a concrete whose water cement ratio is 0.6, the weight of water required for harsh mix, is
8 kg
10 kg
12 kg
14 kg
Log Angles machine is used to test the aggregate for
Crushing strength
Impact value
Abrasion resistance
Water absorption
In counterfort retaining walls, the main reinforcement in the stem at support is
Not provided
Provided only on inner face
Provided only on front face
Provided both on inner and front faces
If 20 kg of coarse aggregate is sieved through 80 mm, 40 mm, 20 mm, 10 mm, 4.75 mm, 2.36 mm, 1.18 mm, 600 micron, 300 micron and 150 micron standard sieves and the weights retained are 0 kg, 2 kg, 8 kg, 6 kg, 4 kg respectively, the fineness modulus of the aggregate, is
7.30
7.35
7.40
7.45
Concrete is unsuitable for compaction by a vibrator if it is
Dry
Earth moist
Semi-plastic
Plastic
The minimum cover in a slab should neither be less than the diameter of bar nor less than
10 mm
15 mm
25 mm
13 mm
If X, Y and Z are the fineness modulli of coarse, fine and combined aggregates, the percentage (P) of fine aggregates to combined aggregates, is
P = [(Z - X)/(Z - Y)] × 100
P = [(X - Z)/(Z - Y)] × 100
P = [(X - Z)/(Z + Y)] × 100
P = [(Z + X)/(Z - Y)] × 100
The condition not applicable to water cement ratio law, is
Internal moisture conditions on hydration continue till complete strength is gained
Concrete specimens may be tested at any temperature
Concrete specimens need be of same age
Concrete specimens need be of same size
The percentage of the aggregate of F.M. 2.6 to be combined with coarse aggregate of F.M. 6.8 for obtaining the aggregates of F.M. 5.4, is
30 %
40 %
50 %
60 %
To hydrate 500kg of cement full water needed, is
100 kg
110 kg
120 kg
130 kg
The dimensions of a 35 litre forma for measuring aggregates by volume, are:
Length 30 cm, breadth 25 cm, height 30 cm
Length 39 cm, breadth 25 cm, height 32 cm
Length 27 cm, breadth 27 cm, height 48 cm
Length 220 cm, breadth 25 cm, height 40 cm
If a beam fails in bond, then its bond strength can be increased most economically by
Increasing the depth of beam
Using thinner bars but more in number
Using thicker bars but less in number
Providing vertical stirrups
The compressive strength of 100 mm cube as compared to 150 mm cube is always
Less
More
Equal
None of the above
How long will it take for the concrete to achieve 100% of its strength?
7 days
14 days
21 days
28 days
The centroid of compressive force, from the extreme compression fiber, in limit state design lies at a distance of (Where xu is the depth of neutral axis at the limit state of collapse)
0.367 xu
0.416 xu
0.446 xu
0.573 xu