Which of the following Pozzolanic materials can be used as mineral admixtures in cement? i. Fly ash ii. Silica fume iii. Rice husk ash iv. Metakaolin
- AOnly (i)
- BOnly (i) and (ii)
- COnly (ii) and (iii)
- D(i), (ii), (iii) and (iv)Correct
Solution
Concept
Pozzolanic mineral admixtures in cement
Formula
NONE
Step-by-step solution
1. Pozzolanic materials react with calcium hydroxide in the presence of moisture to form cementitious compounds. 2. Silica fume and rice husk ash are widely recognized pozzolanic admixtures used in cement concrete. Answer: D
Explanation
Fly ash, silica fume, rice husk ash, and metakaolin are all reactive pozzolanic materials containing high amounts of silica. When blended with cement, they react with calcium hydroxide produced during hydration to form additional cementitious compounds. Consequently, all four materials serve as suitable mineral admixtures, making option D correct.
Why the other options are wrong
A) Statement (i) alone is incomplete as silica fume is also a valid pozzolanic admixture. B) Statements (i) and (ii) combined do not form the correct selection of admixtures.
Shortcut
All 4 listed materials (Fly ash, Silica fume, Rice husk ash, Metakaolin) are valid pozzolanic admixtures.
Common mistake
Assuming only fly ash is used as a mineral admixture and selecting option A instead of recognizing all four listed materials.
Correct answer: D) (i), (ii), (iii) and (iv)