alleryStart learning →Per §10.5, the Himsworth constant K (multiplier of σ) used to obtain target mean strength under the Indian Standard's 5 percent risk factor is:
A1.00
B3.00
C2.20
D1.65
Answer & Solution
Correct answer: D. 1.65
1. §10.5: 'ftarget = fck + 1.65σ' for IS at 5 percent risk
the value 1.65 is Himsworth's constant. American Standard accepts a 2 percent risk factor whose Himsworth constant is 2.2 (Eq. 10.5B).
2. Lower the risk factor, higher the Himsworth constant and the larger the target strength against the same characteristic strength.
_Source: IGNOU ET-522 Block-3 Unit-10 Concrete Mix Design, §10.5, Eq. 10.5/10.5A/10.5B, p. 10_
Keep practising Concrete Mix Design
Browse all Concrete Mix Design questions for B.Tech Civil, or explore more Civil Engineering topics.
Related questions
Tap the steps of the IS Method of mix design in the correct order.Tap TRUE or FALSE for each mix-design / mass-concrete statement.Per Table 10.5 (durability in mix design), the MINIMUM cement content for REINFORCED concrPer Table 10.3, the suggested standard deviation σ for M 20 grade concrete with 'GOOD' degPer §10.7, the Indian Standard method of concrete mix design is described in:Per §10.4, the maximum coefficient of variation V (= σ/μ × 100) accepted by Indian StandarPer §10.5, the area under the normal distribution curve between (μ - σ) and (μ + σ) is appPer §10.4 and IS 456-78, the minimum sample size to determine the standard deviation σ for