With conventional concreting, the quality of work can be controlled when the finished compound is laid. With underwater concrete pouring these advantages are not possible. For these reasons, attention should be paid both to the composition of the concrete and its properties, as well as to the laying technology.
Grain composition, consistency, cement content, maximum cement-water ratio and special chemical and mineral additives are of particular importance for underwater concrete.
It is important that the concrete is not poured directly into the water but is laid through a pipe or hose of a concrete pump permanently immersed in the mixture. Concrete has a higher density than water and easily displaces it. So only a minor part of it is in contact with the water.