Admixtures MCQ with answer and solution

Concept

Accelerators reduce setting time and accelerate early strength development in concrete.

Step-by-step solution

1. Identify the primary function of accelerating admixtures: to increase the rate of hydration of cement. 2. Reduced hydration time leads to faster setting and earlier strength gain. 3. Consequently, finishing operations can begin earlier than usual. 4. Therefore, option (A) is correct while options (B) and (C) describe retarders.

Explanation

Accelerating admixtures are added to concrete to reduce the setting time, which allows finishing operations to begin earlier, especially in cold weather conditions. They increase the rate of early strength gain rather than decreasing it.

Why the other options are wrong

B: Increasing curing time is the opposite of what accelerators do. C: Accelerators increase the rate of strength gain, not decrease it. D: Since B and C are incorrect, 'All of these' is wrong.

Shortcut

Remember: Accelerators speed things up (shorter setting time, faster finishing, higher early strength).

Common mistake

Confusing accelerating admixtures with retarding admixtures which increase setting time and decrease early strength gain.