Indian Standard 456 – 2000 Specifications for High Strength Concrete

In the Indian Standard 456 – 2000, the specifications for high strength concrete are outlined. High strength concrete refers to concrete that has a compressive strength greater than the normal range of concrete. It is designed to withstand higher loads and provide better durability.

Designation of High Strength Concrete
According to Indian Standard 456 – 2000, high strength concrete is designated using a numerical value. The correct answer to the given question is option 'B', which corresponds to the numerical value 5.

Explanation
The numerical designation for high strength concrete in the Indian Standard 456 – 2000 is based on the characteristic compressive strength of the concrete at 28 days. The compressive strength is measured in megapascals (MPa). The higher the numerical value, the higher the compressive strength of the concrete.

Here are the numerical designations for different grades of high strength concrete as per the Indian Standard 456 – 2000:

- M35: High strength concrete with a characteristic compressive strength of 35 MPa.
- M40: High strength concrete with a characteristic compressive strength of 40 MPa.
- M45: High strength concrete with a characteristic compressive strength of 45 MPa.
- M50: High strength concrete with a characteristic compressive strength of 50 MPa.
- M55: High strength concrete with a characteristic compressive strength of 55 MPa.

The numerical designation is based on the 28-day compressive strength because it is a standard time frame for testing concrete strength. However, it is important to note that the actual strength of high strength concrete continues to increase beyond 28 days.

Conclusion
In conclusion, as per the Indian Standard 456 – 2000 specifications, high strength concrete is designated with a numerical value. Option 'B' corresponds to the numerical value 5, indicating high strength concrete with a characteristic compressive strength of 50 MPa.