19/02/2026
☝🏼For the first coat of plastering of EC panel "Poor Mix" will do before using the standard mix after 24 hours.
🔑 Key Points from IS 456:2000
- Nominal Mixes: IS 456 allows nominal mixes up to M20 grade (e.g., 1:2:4, 1:3:6). These are approximate and used for small works.
- Design Mixes: For M25 and above, concrete must be proportioned by mix design (IS 10262) to achieve required strength and durability.
- Minimum Grade for RCC: IS 456 specifies M20 as the minimum grade for reinforced concrete.
- Durability Considerations: Mix selection must account for exposure conditions (mild, moderate, severe, very severe, extreme).
- Poor Mixes (like 1:5:7): Not permitted for structural members because they fail strength and durability requirements. Only suitable for non-load-bearing works like leveling or filling.
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✅ Summary
- 1:5:7 (Poor Mix) → Not allowed for structural concrete under IS 456.
- 1:3:6 (Standard Mix) → Allowed for nominal concrete (M10–M15).
- 1:2:3 (Rich Mix) → Allowed, but usually adjusted to standard grades like M20 or higher through mix design.
Understanding concrete mix ratios is essential for strength, durability, and cost control in construction.
🟡 POOR MIX (1:5:7)
Used for fillings and non-structural works.
⚠ Low strength and chances of cracking.
🟡 STANDARD MIX (1:3:6)
Used for general structural works.
✔ Balanced strength and economy.
🟡 RICH MIX (1:2:3)
Used for foundations and heavy load areas.
⚠ Higher cost and possible shrinkage cracks.
Choosing the correct mix ratio ensures safety, performance, and long-term durability of your structure. Always follow proper site practices and engineering guidelines.
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