the effect of micro silica on permeability and chemical durability of concrete used in the corrosive environment

micro silica (ms) is an extremely fine, spherical powder that is used as an additive for improving concrete performance. it is obtained as a by product of silicon metal and ferrosilicon alloy production.  due to its pozzolanic nature, micro silica can be used to enhance the qualities of both  fresh  and  hardened  concrete. addition of micro silica into the concrete as a cement replacement, decreases its permeability.  as a result, it forms very dense and chemically durable concrete to withstand the harsh and corrosive chemical environments.the results of detailed investigations on concrete made from type v cement with addition of micro silica as substituent and its curing by tap water shows dramatic increase is compressive strength (cs) of concrete after 7 days of hydration onwards.  by repeating experiment in sodium sulfate solutions (50 gr/lit)  prepared under astm c1012 requirements, the results were same as tap water but the extend of increase of compressive strength is lower.  it is also confirmed that, micro silica modies pore size distribution and permeability of type v cement concreats in same way as reported for ordinary portlant cement in various literature. by replacing micro silica as a substituent in type v cement composition, a concreat with high chemical durability and strength are formed, which easily can be used as suitable material for harsh environments such as marine and offshore structures or the places where the concentration of sulfate ions are high, such as concrete sewage pipe line networks.