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 concrete grades mentioned in Eurocode 2 and EN 206-1
| C12/15 | C16/20 | C20/25 | C25/30 | C30/37 | C35/45 | C40/50 | C45/55 | C50/60 |
| Secondary Uses | Usual Uses | |||||||
| C55/67 | C60/75 | C70/85 | C80/95 | C90/105 |
| Special Uses | ||||
Minimum concrete cover of reinforcement steel and minimum suggested concrete grade
| Environmental Conditions Category | ||||
| Usual Conditions (XC2/XC3) | Extreme Conditions (XC4) | Sea-side conditions (XD1/XS1) | Pools (XD2) | |
| Suggested Concrete Grade | C30/37 | C30/37 | C30/37 | C30/37 |
| Minimum Cover | 25 mm | 30 mm | 35 mm | 40 mm |
| Suggested Favorable Concrete Grade | C35/45 | C40/50 | C40/50 | C40/50 |
| Minimum Cover | 20 mm | 25 mm | 30 mm | 35 mm |
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 are assumed using the stipulated concrete grade.
Examples
Example 1: Construction in the sea-side area with a concrete grade of C30/37
Example 2: Construction in the sea-side area with a concrete grade of C40/50 produced with quality assured production procedure
Exceeding a defined limit, the more water the concrete mixture contains, the less its strength and the higher its porosity. Apart from its strength, concrete is also characterized by its workability. Workability defines the amount of water to be used for the production of the mixture. The slump height is the workability criterion of concrete. Depending on the use of the concrete mixture a specific value of slump height is recommended.
Workability concrete classes
Exceeding a defined limit, the more water the concrete mixture contains, the less its strength and the higher its porosity. Apart from its strength, concrete is also characterized by its workability. Workability defines the amount of water to be used for the production of the mixture. The slump height is the workability criterion of concrete. Depending on the use of the concrete mixture a specific value of slump height is recommended.
Concrete amount from 20 m³ to 150 m³
For an amount of concrete greater than 150m³, 12 samples must be taken from 12 different drum mixers. Samples must be taken from different concrete mixers and must be transferred to a certified laboratory for special curing within 20 to 32 hours.
