The grade of concrete is decided on the basis of compressive strength (N/mm2) of concrete cube of 150mm side after 28 days curing.

There are three categories of concrete grades as follows depending upon compressive strength obtained after 28 days curing;

1. Ordinary concrete – In this category, low to medium strength concrete grades are included i.e. M10, M15 and M20. The lean concrete M7.5 is also included in it. It is useful for ordinary PCC and RCC works.

2. Standard concrete – In this, medium to high strength concrete grades are taken i.e. M25, M30, M35, M40, M45, M50 and M55. Such concrete requires concrete mix design. It is useful in mega projects, mass concrete works, etc.

3. High strength concrete – In this, very high strength concrete grades are considered i.e. M60, M65, M70, M75 and M80. It also requires special concrete mix design. It is useful in special type of works like atomic power stations, launching stations, etc.