Question

Let the characteristic strength be defined as that value, below which not more than 50% of the results are expected to fail. 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

• A. 18.42
• B. 21.00
• C. 25.00
• D. 31.58

Answer 1

The correct option is C 25.00

Since characteristic strength has been defined as the value below which not more than 50% of results are likely to fail.

Hence, Target mean strength
= Characteristic strength
$=f_{ck}=25N/m{m}^2$