Which of the following laws states that the strength of cement concrete is only dependent upon water to cement ratio provided the mix is workable?
Correct Answer: A. Abrams’ law
📚 Detailed Explanation: Abrams' Law — The Core Statement
Abrams' Law is the foundational law of concrete strength. Its distinctive feature is the word “only” — strength depends only on the w/c ratio, not on the absolute amounts of water and cement, provided the mix is workable and fully compacted.
Why A (Abrams' law) is correct: Abrams' law states: “For given materials and conditions of test, the quantity of mixing water used per unit of cement is the sole factor (provided the mix is of workable plasticity) that determines the strength of concrete.” Two mixes with the same w/c ratio but different cement contents will have the same strength. Powers' Law (B) is a separate relationship linking gel-space ratio to strength; Stefan's Law (C) is a heat radiation law; Coulomb's Law (D) is an electrostatic law.
Conditions for Abrams' Law to Hold
| Condition | Requirement |
|---|---|
| Mix consistency | Must be workable (not too stiff) |
| Compaction | Must be fully compacted |
| Age | Specimens must be same age |
| Curing | Same curing conditions |
| Materials | Same cement type and aggregate |
Key Concepts for Students
- Abrams' Law: strength depends only on w/c ratio (not on cement content or water content individually).
- Two mixes: Mix A (200 kg water, 400 kg cement = w/c 0.5) and Mix B (150 kg water, 300 kg cement = w/c 0.5) → same strength.
- The law breaks down at very low w/c (below workable range) and for very stiff mixes that cannot be fully compacted.