For given water content, workability decreases if the concrete aggregates contain an excess of
Try it first: pick an option, then read the explanation.
Correct answer: D. All options are correct
Detailed Explanation: Particle Shape and Workability
Why D (All options correct) is correct:All three particle shapes cause increased internal friction and resistance to flow:
Thin particles: High specific surface area → absorb more water → less free water → lower workability.
Flat particles (flaky): Plate-like shape creates high inter-particle contact area and interlocking. Flakiness index >35% is rejected per IS 383.
Elongated particles: Long needle-like shapes bridge across narrow sections, resist flow, and can snap under stress. Elongation index >45% rejected per IS 383.
All three are “undesirable” aggregate shapes that reduce workability by increasing friction and blocking flow.
Undesirable Particle Shapes
| Shape | Problem | IS 383 Limit |
|---|---|---|
| Flaky (flat) | High contact area, interlocking | Flakiness index <35% |
| Elongated (thin, needle) | Bridging, resistance to flow | Elongation index <45% |
| Angular | Surface friction | Use crushed carefully |
- Thin, flat, and elongated particles all reduce workability — all options are correct.
- Cubical/equidimensional aggregates are ideal: maximum volume per unit surface area = least water demand.