Which of the following proportions of concrete mix ingredients is NOT in conformity with the arbitrary method of proportioning?
Correct Answer: D. 1:4:10
📚 Detailed Explanation: Arbitrary Method — Standard Nominal Mixes
Why D (1:4:10) is correct (not conforming): The arbitrary method (also called nominal mix method) specifies fixed ratios of cement : FA : CA from experience. IS 456 recognises specific ratios as standard. The ratio 1:4:10 is not in the standard list of IS 456 nominal mixes. It has an excessively high aggregate ratio that would yield very low strength (below M10) and poor workability.
Standard Nominal Mixes (Arbitrary Method) per IS 456
| Nominal Mix | Grade | In IS 456? |
|---|---|---|
| 1:1:2 | M25 | Yes ✔ |
| 1:1.5:3 | M20 | Yes ✔ |
| 1:2:4 | M15 | Yes ✔ |
| 1:3:6 | M10 | Yes ✔ |
| 1:4:10 | — | No ✘ — not a recognised standard |
- 1:4:10 is NOT a standard IS 456 nominal mix — it does not conform to arbitrary proportioning.
- The four standard nominal mixes are: 1:1:2, 1:1.5:3, 1:2:4, and 1:3:6.