The nominal concrete cover requirement to meet the durability requirement are mentioned below, which of them is not a correct statement?
- ANominal cover for mild exposure is 20 mm
- BNominal cover for moderate exposure is 30 mm
- CNominal cover for severe exposure is 45 mm
- DNominal cover for extreme exposure is 55 mmCorrect
Solution
Concept
IS 456 Table 16
Formula
Mild 20, moderate 30, severe 45, very severe 50, extreme 75 mm
Step-by-step solution
1. IS 456 Table 16: mild 20 mm, moderate 30 mm, severe 45 mm, very severe 50 mm, extreme 75 mm. 2. Extreme exposure is 75 mm, not 55 mm.
Explanation
Option D contradicts the table.
Why the other options are wrong
A, B, C match IS 456.
Shortcut
20-30-45-50-75.
Correct answer: D) Nominal cover for extreme exposure is 55 mm