Topic : Concrete Grades

What are the different grades of concrete?

It's important to know that there are different qualities of concrete. Depending on whether you are pouring concrete for a floor, a foundation, a wall or a pillar, you have to choose the right type to make sure it meets your needs. The quality of concrete is classed by a system of grades called “M” followed by a number. (M5, M7.5, M10, M15, etc.)

In this appellation, “M” means the mix of the concrete. The number followed is a bit more complicated: it is the compressive strength of the concrete mix in Newton per mm² after 28 days of drying. In other terms, after 28 days, the concrete compression is tested to determine the resistance. If the result is 15 Newton per mm² the concrete is a M15 grade. If it resists to 55 Newton per mm² the concrete is a M55 grade. Higher the number, the more resistance it has.

More accurately, a Newton per mm² (N/mm²) equals a megapascal (MPa), which also equals to 145 psi pressure on a concrete block. Concretely, if a block breaks at a pressure test of 6525 psi,  you have to divide it by 145 to find the MPa. In this case, 6525/145=45 which means the concrete is a M45 grade.

The strength of a concrete mix is determined according to the mix ratio between cement, sand and aggregates. The most common grade of concrete for a floor is a standard grade which is between M25 and M45.

See more examples in the table below: