Characteristic strength of concrete.

The classification of concrete grades is based on their compressive strength. Each concrete grade e.g. C30/37 is characterized by two equivalent strengths, which in this specific example are 30 MPa and 37 MPa. The first is the characteristic strength fck of a standard concrete cylinder and the latter is the characteristic strength of a standard concrete cube.

The protection of reinforcement steel against corrosion depends on the porosity, the quality and the thickness of the concrete cover. The density and quality of the concrete cover is assumed using the stipulated concrete grade.