RussTech Condensed Silica Fume is manufactured from the highest grade silica fume and is used to produce ultra-high strength, high durability concrete. Consensed Silica Fume consists of highly reactive ultra-fine particles and contains 92% to 97% silicon dioxide and has an average specific gravity of 2.20. Other silica fumes, with lower amounts of silicon dioxide, may contain other unwanted elements and compounds such as carbon. Higher levels of carbon, as indicated by loss on ignition, darken concrete and can lead to problems with entrained air.