Silica fume is also referred to as micro silica or condensed silica fume but the term silica fume has been generally accepted. It is a by-product of manufacture of silica and ferrosilicon alloys from high purity quartz and coal in a submerged arc electric furnace. It is reported that the addition of ultra fine particle in HPC improves the strength of concrete. The optimum silica fume proportions in between 20% and 25% by weight of concrete. In it self silica fume does not have any binding properties, but it reacts with calcium hydroxide on hydration of cement and produces the gel i.e. calcium silicatehydrate which has good binding properties. Silica fume has been used in manufacture of high strength concrete.. .