Sika 4a Water Stop Admixture is a rapid setting, ready to use, Chloride and solvent free waterproofing admixture. When mixed with ordinary Portland cement and water, it sets rapidly to seal areas of severe water infiltration through concrete, rock or masonry. Sika 4a is used as preliminary waterproofing work on wet surfaces or where there is general infiltration of water, prior to the application of subsequent cementitious render or gunite. Typical applications are tunnels and culverts, mine galleries, water reservoirs, concrete pipes and manholes. Sika 4a Water Stop Admixture can also be used in quick setting mortar for assembly work, e.g. for fixing anchors, bolts and other fitting subject to early loading in rock or concrete