# What is Grades of Concrete ?

As an Civil Engineer you could have come across the mentions of grades of concrete such as :

• M25 concrete for the RCC work in a foundation.
• M20 concrete for the roof slab.
• M15 concrete for PCC works etc. ## Have you ever wondered what do these grades of concrete M25, M20, M15 etc really represents ?

These names represents the grade of concrete. In this the grade of concrete is represented by prefixing ‘M’ followed by the number where M stands for mix and number denote the minimum compressive strength of concrete of 15 centimeters cube at 28 days and expressed in Newton per millimeter square(N/mm²). These grade of concrete also represents various mix ratio of cement: fine aggregates: coarse aggregates.

MPa (N/mm²)
M55 MPa
M7.57.5 MPa
M1010 MPa
M1515 MPa
M2020 MPa
M2525 MPa
M3030 MPa
M3535 MPa
M4040 MPa
M4545 MPa
M5050 MPa
M5555 MPa
M6060 MPa
M6565 MPa
M7070 MPa

For example : M20 concrete represents mix ratio of 1: 1.5: 3, that is for every one part of cement we should add 1.5 part of sand and 3 part of coarse aggregates is mixed as per Indian Standard Code. There are three major groups of concrete such as ordinary concrete, standard concrete and high strength concrete and there are total of 15 grades of concrete. Different grade of concrete have different compressive strength.

Each grade of concrete represents some mix ratio. In general there are two types of concrete mixes such as nominal mix and design mix. The nominal mixes are those whose mix ratio is defined which includes grades of concrete up to M25. Below table shows the different grades of concrete falling under nominal mix.

`Also Read : Cement Concrete Specification for Design Mix 1:2:4`