Question

Which of the following agent does not enhance the workability of concrete?

• A. Plasticizer
• B. Silica fume
• C. Air entraining agents
• D. Super plasticizer

Hint:

Remember: Chemical admixtures like plasticizers improve workability, while mineral admixtures like silica fume generally reduce it and are added for strength or durability benefits.

Answer 1

The Correct Option is B

Workability of concrete refers to how easily it can be mixed, placed, compacted, and finished without segregation. Several chemical admixtures are used to improve the workability of concrete:
- Plasticizers and Superplasticizers reduce water content and improve flow.
- Air entraining agents introduce tiny air bubbles that enhance workability and resistance to freeze-thaw cycles.
On the other hand, Silica fume is a pozzolanic material used to increase the strength and durability of concrete. However, it actually reduces workability due to its very fine particle size and high surface area, which increases water demand.
Hence, among the given options, silica fume does not enhance workability. \[ \text{Answer: Silica fume} ⇒ \text{Reduces workability} \]