Concrete recycling
As a concrete recycling the reproduction and re-use of concrete and its components is called.
Depending on the time of recycling distinction is made between fresh and hardened concrete recycling. The fresh concrete can be recycled concrete residues that occur eg in the production of concrete and are not yet substantiated. When hardened concrete recycling, however, the hardened concrete is processed, which is obtained, for example, the demolition of buildings.
Fresh concrete recycling
When fresh concrete recycling is not yet hardened concrete residues are washed with water and then separated the aggregate from cement paste. The aggregate may be supplied after the subsequent sieving again the concrete. The resulting when washing the concrete residues and also during washout of truck mixers resulting residual water contains cement grains and other fines and may be added to the mixing water in accordance with DIN EN 1008 for concrete production. This is referred to as residual water recycling. The allowable ratio of residual water to fresh water for a new mixture depends on the fines content of the residual water and the required quality of the concrete. Concretes are made on the particularly high demands ( high-strength concrete, air-entrained concrete, ... ) may be usually mixed with fresh water only.
Fresh concrete recycling is practically run by all German concrete manufacturers. In the preparation applicable residual concrete can be fed again by the process almost completely of concrete production.
Hardened concrete recycling
The recycling of solid concrete starts with the demolition of buildings by an unmixed possible presorting. Concrete demolition is then crushed by crusher concrete gravel and crushed stone. From the demolition of reinforced concrete, this includes the sorting of reinforcing steel. This steel scrap may be formed by melting into new steel products.
Concrete gravel and crushed stone are available for various purposes. With crushing for concrete chippings recycled concrete can be produced. The requirements for these " recycled aggregate " are defined in the German standard DIN 4226-100. Since concrete chippings which was used in the production always from the natural aggregate and consists of adhering cement stone, a modified water right must be taken into account in the production of recycled concrete and others.
Another major area of application for gravel and sand from the hard concrete recycling is the road maintenance and construction. Concrete chippings can be used eg for unbound base, replacing grit from primary sources.
Separation of the material according to particle size
Dust in sorting
Loading of concrete chippings