Concrete is divided into different compressive strength classes according to its respective compressive strength according to DIN EN 206, Tables 12 and 13. These denote the quality of the concrete in terms of its resistance to external pressure. The characteristic strength of test cylinders and test cubes at a test age of 28 days is used for classification. A basic distinction is made between normal or heavy concrete (abbreviation C) and lightweight concrete (abbreviation LC).
The compressive strength class in the respective concrete type is described with two values:
1. Value: Characteristic minimum strength ∫ck, cyl of cylinders in N/mm².
Measurements are taken using a test cylinder with a diameter of 15 cm and a length of 30 cm.
2. Value: Characteristic minimum strength ∫ck, cube of cubes in N/mm².
Measurements are taken using a test cube with an edge length of 15 cm.
Example: C(20/25) stands for normal/heavy concrete with ∫ck, cyl= 20 N/mm2 and ∫ck, cube= 25 N/mm2.
The values range from C8/10 to C100/115 and LC8/9 to LC80/88. Common compressive strength classes for basement walls made of in-situ concrete are e.g. C25/30 or C30/37.
Source: bauwion
