Which of the following statements is INCORRECT about the grading limits of fine aggregates?
- AZone II corresponds to normal sand.
- BThere are 3 grading zones as per IS 383-2016.Correct
- CZone III corresponds to finer sand than Zone II.
- DIS 383 defines the grading zones of fine aggregates.
Solution
Concept
IS 383 divides fine aggregate into 4 grading zones (Zone I to Zone IV), from coarse to fine.
Step-by-step solution
1. IS 383 gives grading limits for fine aggregate. 2. It defines 4 zones: Zone I (coarsest), II, III and IV (finest). 3. Zone II is normal or medium sand, and Zone III is finer than Zone II. 4. Statement B says there are 3 zones. This is wrong. 5. So the answer is (B).
Explanation
IS 383 gives four grading zones for fine aggregate, not three. Sand becomes finer from Zone I to Zone IV. So statement B is the incorrect one.
Why the other options are wrong
A: Correct, because Zone II is normal or medium sand. C: Correct, because Zone III is finer than Zone II. D: Correct, because IS 383 defines these zones.
Shortcut
Remember 'four zones, I to IV, coarse to fine'.
Common mistake
Thinking there are 3 zones, or thinking Zone I is the finest. Zone I is actually the coarsest.
Correct answer: B) There are 3 grading zones as per IS 383-2016.