Colcrete:
Colcrete is grouted and is generally suitable for underwater. It is made by introducing colgrout into the voids of pre-placed coarse aggregates by injection method. The surface area of coarse aggregate in 1 m3 of concrete amounts to about 68800 m2 in the conventional concrete of 1 : 2 : 4 mix. Practically, it is difficult to wet and activate the above area.
Properties
(a) The separation of smaller particles of cement is achieved efficiently.
(b) It makes it nearly immiscible in water. It prevents aggregation of sand and reduces bleeding to a minimum.
(c) Its fluidity allows it to be pumped to considerable distances to the point of placement.
(d) Every particle of cement in the mix is completely wetted. The cement is thoroughly mixed with other constituents.