Let the characteristic strength be defined as that value, below which not more than 50% of the results are expected to fall. Assuming a standard deviation of 4 MPa, the target mean strength (in MPa) to be considered in the mix design of a M25 concrete would be

Workability of concrete can be measured using slump, compaction factor and Vee bee time. Consider the following statements for workability of concrete:

(i) As the slump increases, the Vebe time increases

(ii) As the slum increases, the compaction factor increases

Which of the following is TRUE?

Consider the following statements for air-entrained concrete:

(i) Air-entrainment reduces the water demand for a given level of workability

(ii) Use of air-entrained concrete is required in environments where cyclic freezing and thawing is expected.

Which of the following is TRUE?

The modulus of elasticity, E = 5000$$\sqrt{{\mathrm f}_\mathrm{ck}}$$ where f_ck is the characteristic compressive strength of concrete, specified in IS:456-2000 is based on