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Concrete pavements are exceptionally resistant to pressure loads. Their robustness enables them to permanently withstand even the point loads of heavy steel containers. It is precisely that property which has contributed to the material’s success in road construction in times of increasing volumes of heavy traffic. In addition to industrial areas and agricultural roads that are subject to extremely high loads, concrete plays a major role also in the construction of motorways and airport runways.
The basic formula of concrete is as proven as it is simple: Additives like sand, chippings or gravel are mixed with water and the binding agent cement. Cement consists of limestone and clay. Together with the water, it forms the cement paste which causes the construction material to set into artificial rock. Depending on its composition, the properties of cement range from heavy to light, from pressure-resistant to heat-insulating. Concrete is also ideally suited for recycling.
Concrete is available in various strength classes. The only strength classes suitable for road construction, however, are types B 35 to B 55, as they are capable of taking particularly high loads. The designation of concrete as class B 55 concrete indicates that each single square millimetre is capable of absorbing a pressure of 55 newton. Concrete tends to cracking, on the other hand, when exposed to tensile stresses. That is why concrete is often reinforced with steel, which is capable of absorbing extremely high tensile forces. In road construction, steel is inserted into the concrete as dowel bars or tie bars during the paving operation. Alternatively, steel mats or pre-shaped reinforcing profiles are laid out prior to the concrete paving operation.
