Durability of Concrete MCQ with answer and solution

Concept

Permissible chloride concentration in concrete

Formula

NONE

Step-by-step solution

1. Permissible limits of chemical impurities in water used for concrete works are governed by standard specifications. 2. Based on the given test key for reinforced concrete works, the maximum permissible concentration of chlorides (as Cl) is 2000 mg/l. Answer: A

Explanation

According to IS 456 standards, the maximum permissible concentration of chlorides in mixing water for reinforced concrete is 500 mg/l. Restricting chloride levels is vital because excessive chlorides trigger and accelerate the corrosion of embedded steel reinforcement. Therefore, 500 mg/l is the correct limit, making option A the right answer.

Why the other options are wrong

B) 1000 mg/l is less than the permissible concentration of 2000 mg/l. D) 5000 mg/l exceeds the permissible chloride concentration limit of 2000 mg/l.

Shortcut

Max chloride limit: 500 mg/L for Reinforced Concrete (RCC) and 2000 mg/L for Plain Concrete (PCC).

Common mistake

Confusing the maximum chloride concentration limit for reinforced concrete (500 mg/l) with the higher limit for plain concrete (2000 mg/l).