Assertion (A): High-strength concrete mixes often utilize Fly Ash as a partial replacement for cement. Reason (R): Fly Ash improves the workability of the fresh mix and enhances long-term strength through pozzolanic reactions. Choose the correct answer: (A) Both (A) and (R) are correct and (R) is the correct explanation of
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)Correct
- BBoth (A) and (R) are correct, but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is incorrect
- D(A) is incorrect but (R) is correct
Solution
Concept
Fly Ash in Concrete and Pozzolanic Reaction
Formula
N/A
Step-by-step solution
1. Analyze Assertion (A): High-strength concrete mixes often utilize Fly Ash as a partial replacement for cement. 2. Analyze Reason (R): Fly Ash improves fresh mix workability and increases long-term strength via pozzolanic reactions. 3. Conclude that both (A) and (R) are correct and (R) is the correct explanation of (A), selecting Option (a).
Explanation
Both statements are correct and directly related. High-strength concrete often uses fly ash because spherical fly ash particles make fresh concrete easier to mix and pour (improving workability). Over time, fly ash reacts with calcium hydroxide in the concrete (pozzolanic reaction) to form additional strength-giving compounds, which significantly boosts its long-term strength and durability.
Shortcut
To remember the benefits of Fly Ash in concrete, use the mnemonic "FLY": - Flow/Workability: Spherical particles act like tiny ball bearings to improve fresh mix workability. - Long-term Strength: Pozzolanic reaction generates additional strength-giving compounds over time. - Yields Durable High-Strength Mixes: Provides the ideal technical reason for replacing part of the cement in high-strength concrete.
Common mistake
A common mistake is selecting option B by believing that Reason (R) is merely an independent true statement and not the explanation for Assertion (A). Students often fail to connect that the improved workability and pozzolanic reactions described in (R) are the direct technical reasons why Fly Ash is successfully utilized as a partial replacement for cement in high-strength concrete mixes.
Correct answer: A) Both (A) and (R) are correct and (R) is the correct explanation of (A)