Per the worked illustrative example in §10.9 (M 20, 20 mm angular, 0.9…

Question

Per the worked illustrative example in §10.9 (M 20, 20 mm angular, 0.90 CF, good control, mild exposure), the computed TARGET mean strength comes out to be approximately:

Accepted Answer

B. {'text': '27.6 N/mm-square', 'label': 'B'}

1. §10.9 Step 1: ftarget = fck + Kσ = 20 + 1.65 × 4.6 = 27.6 N/mm². σ = 4.6 is read from Table 10.3 for M20 + good control.
2. The example then picks w/c = 0.50 from Fig 10.6 (lower of the durability cap 0.65 and Abrams 0.50).
_Source: IGNOU ET-522 Block-3 Unit-10 Concrete Mix Design, §10.9 Step 1, p. 20-21_

Answer

{'text': '20.0 N/mm-square', 'label': 'A'}

Answer

{'text': '35.0 N/mm-square', 'label': 'C'}

Answer

{'text': '60.0 N/mm-square', 'label': 'D'}