Silica Fume Versus Other Forms Of Synthetic Silica
Several other amorphous silica products are occasionally confused with silica fume. These products are purposely made, and while they offer the potential of performing well in concrete, they are typically too expensive for such use.
These products are made through three processes:
Fumed silica—Fumed silica is produced by a vaporphase hydrolysis process using chlorosilanes such as silicon tetrachloride in a flame of hydrogen and oxygen. Fumed silica is supplied as a white, fluffy powder.
Precipitated silica—Precipitated silica is produced in a finely divided form by precipitation from aqueous alkali-metal silicate solutions. Precipitated silica is supplied as a white powder or as beads or granules.
Gel silica—Gel silica is also prepared by a wet process in which an aqueous alkali-metal silicate solution is reacted