Pick up the correct statement from the following.
Correct Answer: D. All options are correct
📚 Detailed Explanation: Effects of Water Quantity on Concrete
The quantity of water in a concrete mix must be optimised — both too little and too much cause significant defects in fresh and hardened concrete.
Why D (All options are correct) is correct:
Statement A — Insufficient water makes mix harsh: At very low water content, the mix has a high internal friction and does not flow. The mix feels “harsh” or “stony” — the paste cannot coat aggregate surfaces adequately and the mix balls up during mixing.
Statement B — Insufficient water makes mix unworkable: A harsh mix has very low workability (high VB time, near-zero slump) and cannot be placed or compacted without leaving voids and honeycombing.
Statement C — Excess water causes segregation: Above a critical w/c, the mix becomes so fluid that heavier aggregates settle while lighter cement and water rise — this is segregation. It destroys uniformity and reduces strength dramatically.
Statement A — Insufficient water makes mix harsh: At very low water content, the mix has a high internal friction and does not flow. The mix feels “harsh” or “stony” — the paste cannot coat aggregate surfaces adequately and the mix balls up during mixing.
Statement B — Insufficient water makes mix unworkable: A harsh mix has very low workability (high VB time, near-zero slump) and cannot be placed or compacted without leaving voids and honeycombing.
Statement C — Excess water causes segregation: Above a critical w/c, the mix becomes so fluid that heavier aggregates settle while lighter cement and water rise — this is segregation. It destroys uniformity and reduces strength dramatically.
Effect of Water Content on Mix Quality
| Water Content | Problem | Effect |
|---|---|---|
| Too little (<0.35) | Harsh, unworkable | Incomplete compaction, voids |
| Optimal (0.40–0.55) | None (design range) | Good workability + strength |
| Too much (>0.65) | Segregation, bleeding | Weak, non-uniform concrete |
Key Concepts for Students
- The w/c ratio must be in an optimal window: high enough for workability, low enough for strength and cohesion.
- A harsh mix (too little water) is as bad as a segregated mix (too much water) — both produce defective concrete.