Prevents Rising, Falling & Penetrating Damp Additive to Mortar, Screed, Unreinforced Concrete and Plaster Remedy for Leaks Coprox Waterproof Cement Additive is an excellent primary waterproofing when mixed with mortar, screed, unreinforced concrete or plaster. It is an essential ingredient in the construction of structural, retaining and boundary walls, floors, showers, basements, wine cellars, underground parking, ponds, swimming pools, reservoirs and water features for the prevention of rising, falling and penetrating damp. Coprox Waterproof Cement Additive is also an excellent remedy for the plugging of leaks.