Grades Of Concrete:
In IS: 456-1978, the different grades of concrete are given as M10, M25, M20, M25, M30, M35, and M40. In the classification of concrete mix, the letter M denotes the Mix and the numbers 10, 15, 20, 25, 30, 35, 40 represent the predetermined works cube strength of 15 cm cubes after curing of 28 days in N/mm2.
The works cube strength refers to the strength achieved by the concrete after 28 days curing. It can also be defined as the crushing strength of concrete cubes at 28 days. The compressive strength of the concrete should not be greater than 5% of the test results are expected to fall. The list of specified concrete grades are given below:
|Grade Of Concrete||Specified Compressive Strength At 28 Days (N/mm2)|
Note 1: M5 and M7.5 concrete also exist which can be used in lean concrete bases/mud and for ordinary masonry wall foundation.
Note 2: Concrete grade less than M15 should not use in reinforced concrete.
Note 3: M10, M15, M20…. concrete approximately equal to 1:3:6, 1:2:4, 1:1.5:3… nominal mix.