Question

Find the compressive strength below which 50% test results are expected to fall for M20 concrete

• A. 20
• B. 26.6
• C. 13.4
• D. 30

Answer 1

The correct option is B 26.6

50% Test results fall below mean compressive strength $f_m$

$f_m=f_{ck}+1.65\sigma$

$=20+1.65\times 4$

$=26.6MPa$

[M20 has $f_{ck}=20MPa$ and $\sigma =4MPa$ ]