Workability of concrete is directly proportional to
Correct Answer: C. Grading of aggregate
📚 Detailed Explanation: Grading of Aggregate and Workability
Why C (Grading of aggregate) is the answer: Well-graded aggregate (following Fuller's curve or IS grading zones) produces a denser packing with smaller voids. In a well-graded mix, fine particles fill the voids between coarser ones, creating a smoother mass that requires less effort to compact and flow. This denser, void-minimising packing = better workability for a given water content.
Note on option D: Water-to-cement ratio is also directly proportional to workability, but this question's official answer key selects (C) grading. This indicates the question is testing specifically which characteristic of aggregate affects workability directly — and the answer is grading quality, not w/c ratio (which belongs to mix design, not aggregate properties).
Aggregate Grading and Workability
| Aggregate Grading | Workability Effect |
|---|---|
| Well-graded | Higher workability (efficient void filling) |
| Gap-graded / poorly graded | Lower workability (excessive voids) |
| Single-sized coarse only | Very low workability (too many voids) |
- Grading of aggregate is directly proportional to workability of concrete.
- IS 383 specifies four grading zones (I-IV) for fine aggregates to ensure optimal packing and workability.