For which of the following grades is ordinary concrete not used?
Correct Answer: B. M40
📚 Detailed Explanation: Concrete Grade Classification (IS 456)
Why B (M40) is correct: IS 456:2000 Table 2 classifies concrete into three groups:
• Ordinary concrete: M10, M15 only
• Standard concrete: M20, M25, M30, M35, M40, M45, M50, M55
• High performance concrete: M60, M65, M70, M75, M80
M40 belongs to Standard concrete, not Ordinary concrete. M10 (A) is ordinary concrete, M20 (C) is standard, M25 (D) is standard. Only M40 (B) is not ordinary, making it the correct answer to “which grade is NOT ordinary concrete.”
• Ordinary concrete: M10, M15 only
• Standard concrete: M20, M25, M30, M35, M40, M45, M50, M55
• High performance concrete: M60, M65, M70, M75, M80
M40 belongs to Standard concrete, not Ordinary concrete. M10 (A) is ordinary concrete, M20 (C) is standard, M25 (D) is standard. Only M40 (B) is not ordinary, making it the correct answer to “which grade is NOT ordinary concrete.”
IS 456 Concrete Grade Classification
| Classification | Grades |
|---|---|
| Ordinary concrete | M10, M15 |
| Standard concrete | M20 to M55 |
| High performance concrete | M60 to M80 |
- Ordinary concrete is only M10 and M15.
- M40 is Standard concrete — definitely NOT ordinary concrete.
- For M25 and above, IS 456 mandates design mix (not nominal mix) to be used.