Silica Fume is also called Micro silica, it is a very fine pozzolanic material, composed of amorphous silica produced by electric arc furnaces as a by-product of the production of elemental silicon or ferro silicon alloys. This micro silica used in refractory has a minimum of 92% content of silica, the average content of SiO2 is around 93%. And this undensified micro silica reaches national first grade standard,80% of granularity is less than 0.1 um with a maximum of 0.3 um.