Calcium silicates are a set of four compounds obtained by reacting calcium oxide and silica in various ratios. These have compositions Ca3O.SiO4, Ca2SiO4, Ca3Si2O7 and CaSiO3. Calcium orthosilicate is a white powder with the chemical formula Ca2SiO4. It has a low bulk density and high physical water absorption. It is used as an anti-caking agent and an antacid. A white free-flowing powder derived from limestone and diatomaceous earth, calcium silicate has no known adverse effects to health. It is used in roads, insulation, bricks, and roof tiles.
Industrial grade piping and equipment insulation is often fabricated from calcium silicate. Its fabrication is a routine part of the curriculum for insulation apprentices. Calcium silicate competes in these realms against rockwool as well as proprietary insulation solids, such as perlite mixtures and vermiculite bonded with sodium silicate.
One of the most successful materials in fireproofing in Europe is calcium silicate. Where North Americans use spray fireproofing plasters, Europeans are more likely to use cladding made of calcium silicate. Calcium silicate is easily damaged by water. Therefore, silicone treated sheets are available to fabricators to mitigate potential harm from high humidity or general presence of water. Fabricators and installers of calcium silicate in passive fire protection often also install firestops.