Lexicon DIY-Knowledge

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Concrete is the most common building material in civil and underground engineering and construction. There are three categories:

- Concrete with its three sub-groups (lightweight aggregate, standard and heavy or high-density concrete)

- Bricks and building stones made of concrete

- Prefabricated building elements made of concrete

Concrete consists of cement and water as bonding agents to which various aggregates are added of which sand and pebbles are the most common. The aggregates are chosen for their particle size and grading curve and then combined in a mixing process. The concrete is then poured into the formwork or shuttering while still wet where it is left to set. Once the hardening time has elapsed, the set concrete has the required compression resistance and can be subjected to stress.

The sub-groups light-weight concrete, standard concrete and heavy concrete differ according to the type and consistency or strength of their aggregate substances. The nominal strength or compression resistance is marked by a sequence of numbers and letters:

B 25 stands for standard concrete with a compression resistance of 25 N/mm². There are various intermediate values before the top class concrete B 55 is reached.

In order to reach the tensile strength of reinforced concrete, non-prestressed constructional steel is embedded in standard concrete. A prestressed constructional steel grid is used to produce prestressed reinforced concrete.