As per IS 456-2000, the minimum cover required for the design of a water tank in severe exposure condition should not be less than
- A30 mm
- B45 mmCorrect
- C50 mm
- D75 mm
Solution
Concept
Minimum clear cover for severe exposure
Formula
NONE
Step-by-step solution
1. IS 456-2000 Table 16 specifies nominal cover requirements for reinforcement based on environmental exposure. 2. Severe exposure conditions require enhanced cover thickness to protect embedded steel reinforcement. 3. Under severe exposure conditions, the minimum required cover is 45 mm. Answer: B
Explanation
Concrete water tanks exposed to severe environmental conditions require enhanced nominal concrete cover to protect steel reinforcement from aggressive chemical and liquid ingress. As per durability specifications referenced in IS codes, severe exposure generally mandates a nominal cover of at least 45 mm. This prevents premature corrosion of rebar and structural deterioration from moisture penetration.
Why the other options are wrong
A) 30 mm cover is specified for moderate exposure conditions. C) 50 mm cover is specified for very severe exposure conditions. D) 75 mm cover is specified for extreme exposure or concrete cast directly against earth.
Shortcut
Minimum cover for severe exposure condition = 45 mm.
Common mistake
Confusing the nominal cover for severe exposure (45 mm) with moderate exposure (30 mm).
Correct answer: B) 45 mm