If the concrete ingredients (cement : sand : aggregates) are in the ratio 1:3:6, the grade of concrete is:
Correct Answer: A. M10
📚 Detailed Explanation: Nominal Mix Ratio 1:3:6 = M10
Why A (M10) is correct: 1:3:6 is the leanest standard nominal mix — the lowest cement content, highest aggregate proportion. This produces concrete with a 28-day characteristic compressive strength of approximately 10 N/mm², hence designated M10.
Complete Nominal Mix Chart (IS 456)
| Nominal Mix | Grade | fck (N/mm²) | Typical Application |
|---|---|---|---|
| 1:3:6 | M10 | 10 | Plain concrete, levelling courses, blinding |
| 1:2:4 | M15 | 15 | Foundations, mass concrete, non-structural |
| 1:1.5:3 | M20 | 20 | General RCC — minimum for reinforced members |
| 1:1:2 | M25 | 25 | Pre-stressed, high-quality RCC |
- 1:3:6 = M10 — leanest standard mix, used for non-structural applications.
- IS 456 does not permit M10 for reinforced concrete members (minimum M20 for RCC).