The strength of concrete is very much dependent upon the hydration reaction just discussed. Water plays a critical role, particularly the amount used. The strength of concrete increases when less water is used to make concrete. Water proofing compounds can be used to improve the pore structure of concrete and hence to reduce the water permeability of concrete. Nowadays, a number of waterproofing products are available in market which works on reduction of permeability of concrete. Few of them are required to be added while mixing the concrete ingredients and few others are applied on the concrete surface. The colour of groundmass changes with addition of micro-silica and it become dark in colour and confirm the increase in binding property of cementitious material. Reaction rim develops in case of cement with micro-silica. Binding material is more uniform in case of concrete with micro-silica than the concrete without micro-silica. The addition of micro-silica gives high strength, more durable and uniformly distributed binders in concrete.