The shotcrete concrete (topcrete concrete) is very much like a composition of ordinary concrete but has specifics in its production and laying. The size of the large chunks of additives is Dmax 8 mm. The maximum water content is 0.50 and the cement content is between 360-420 kg/m³. Production is carried out in two processes: wet and dry.
In the wet process, the mixture is prepared in advance ready to be pumped by concrete piston or screw pump. At the end of the hose there is a nozzle in which compressed air is inserted under pressure together with a chemical additive, which acts as an accelerator after spraying the mixture to increase faster solidity.
In the dry spraying process the cement and the aggregates are mixed without water. The dry mixture is transported in a stream of compressed air through a hose to a mixing nozzle. In the nozzle section the mixture is mixed with water and a chemical additive and is applied in a continuous stream.