Question

Calculate the target mean compressive strength at 28 days curing, for M20 grade concrete, as per IS 10262-2009 (take standard deviation as 4 N / mm²).
1. 26.6 N / mm²
2. 20.0 N / mm²
3. 22.4 N / mm²
4. 28.7 N / mm²

Answer 1

Correct Answer - Option 1 : 26.6 N / mm²

Concept:

The correct expression as per IS 456: 2000 to find Target mean strength is:

fcm = fck + (1.65 × σ)

fcm = Target mean strength

fck = Characteristic strength

σ = Standard deviation

1.65 is generally a risk factor

Calculations:

fck = 20 N/mm2

σ = 4.0 N/mm2

Target mean strength is:

fcm = fck + (1.65 × σ)

fcm = 20 + (1.65 × 4)

fcm = 26.6 N/mm2