Silica fume, also called Microsilica, is a byproduct of producing silicon metal or ferrosilicon alloys. Silicon metal and alloys are produced in electric furnaces. The raw materials are quartz, coal, and woodchips. The smoke that results from furnace operation is collected and sold as silica fume, rather than being land filled. Silica fume consists primarily of amorphous (non-crystalline) silicon dioxide (SiO2), its average granule diameter is 0.15~0.20 µm,specific surface area is 15000~20000 m2/kg, and it has extremely strong surface active.