What are the different grades of concrete?
Its important to know that there is different quality of concrete. Depending if you are pouring concrete for a floor, foundations, a wall or a pillar, you have to choose the right type to make sure it answers your needs. The quality of concrete is classed by a system of grades called by a “M” followed by a number. (M5, M7.5, M10, M15, etc.)
In these appellations, the “M” means the mix of the concrete. The number following 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 how it resist. If the results say it resist to 15 Newton per mm2 the concrete is a M15 grade. If it resists to 55 Newton per mm2 the concrete is a M55 grade.
More accurately, a Newton per mm2 (N/mm2) equals a megapascal (MPa), which also equals a 145 psi pressure on a concrete block. Concretely, if a block in a test breaks at a pressure of 6525 psi, divided by 145, it equals 45 MPa, 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: