Per §10.8 (IS Method, Step 1), the target mean strength for mix design…

Question

Per §10.8 (IS Method, Step 1), the target mean strength for mix design is computed as:

Accepted Answer

A. {'text': 'f_target = f_ck plus K times σ, with K being the Himsworth constant', 'label': 'A'}

1. §10.8 Step 1 gives Eq. 10.7A: 'ftarget = fck + Kσ', where fck is the characteristic strength at 28 days, σ is the standard deviation and K is Himsworth's constant (= 1.65 for IS).
2. Step 1 also allows σ to be read from Table 10.3 for the chosen grade and degree of control if 30 prior cubes are not available.
_Source: IGNOU ET-522 Block-3 Unit-10 Concrete Mix Design, §10.8 Step 1 and Eq. 10.7A, p. 15_

Answer

{'text': 'f_target = f_ck minus K times the standard deviation σ of cube tests', 'label': 'B'}

Answer

{'text': 'f_target = f_ck multiplied by K and by σ in a single product term', 'label': 'C'}

Answer

{'text': 'f_target = the sum (f_ck plus σ) divided by the Himsworth constant K', 'label': 'D'}