Test: Properties of Concrete - Civil Engineering (CE) MCQ

Splitting cylindrical test:

• The cylindrical sample is laid horizontal and it is subjected to the compressive load in the UTM machine.
• During this tensile stress is developed in the middle 5/6 portion of the section of the cylinder due to which its failure takes place.
• This test gives a more uniform and accurate result.
• The greatest advantage of this test is the same sample is used to find the compressive strength of the concrete.

The magnitude of the tensile stress is obtained by –

where, P = Applied load, D = Diameter of the cylinder, L = Length of the cylinder

Based on the state of concrete, its properties vary. Concrete in the fresh state has different properties than concrete in a hardened state.

Bleeding can be good as well as bad for fresh concrete. Sometimes due to improper mixing, the water forms a thin layer on the outer surface, by oozing out through voids.

Higher the cement content i.e. lower the aggregate cement ratio, higher is the strength. It improves workability also.

Aggregates should provide space for cement paste so as to lubricate the area. The parameters like texture, size, shape, grading are to be considered. Larger size, cubical, round and rough textured aggregates are preferred.

1:2:4 concrete mix denotes, 1 part of cement, 2 parts of sand, and 4 parts of coarse aggregate in that particular concrete mix.
1 m³ freshly mixed concrete corresponds to 1.54 m³ dry volume of concrete.
Calculation:
Given,
Wet volume of concrete = 150 Cum, Concrete mix = 1:2:4
1 m³ freshly mixed concrete corresponds to 1.54 m³ dry volume of concrete.
150 m³ freshly mixed concrete corresponds = 150 × 1.54 = 231 m³ dry volume of concrete
In a concrete mix of 1:2:4, Total parts = (1 + 2 + 4) = 7
In a total of 7 parts, cement volume is 1 part, i.e. 1/7
Hence, Cement volume for 231 m³ dry concrete = (1/7) × 231 = 33 m³

The assumed value of standard deviation for initial calculations as per IS 456 – 2000 are given below in the table:

Aggregates should provide space for cement paste so as to lubricate the area. The parameters like texture, size, shape, grading are to be considered. Larger size, cubical, round and rough textured aggregates are preferred.

It increases with increase in age. The strength measured after days, months and years shows an increase. It takes 28 days for concrete to attain full strength. However, it continues to attain strength even after 28 days.

Bleeding can be good as well as bad for fresh concrete. Sometimes due to improper mixing, the water forms a thin layer on the outer surface, by oozing out through voids.