Minimum cover for 16 mm diameter bar placed as a main reinforcement in the rib for precast reinforced concrete ribbed slab unit shall be
- A16 mm
- B20 mmCorrect
- C24 mm
- D32 mm
Solution
Concept
Cover to main bars in precast ribs
Step-by-step solution
1. Cover to main reinforcement is not less than the bar diameter and not less than 20 mm in mild exposure. 2. For a 16 mm bar the minimum cover is 20 mm.
Explanation
The larger of bar diameter (16) and the minimum cover (20) governs.
Why the other options are wrong
16 mm is below the minimum cover; 24 and 32 mm are not required.
Shortcut
Cover ≥ max(φ, 20 mm).
Correct answer: B) 20 mm