<P> Calcium silicate is a white free - flowing powder . It can be derived from naturally occurring limestone and diatomaceous earth, a siliceous sedimentary rock . It is one of a group of compounds that can be produced by reacting calcium oxide and silica in various ratios e.g. 3CaO SiO, Ca SiO; 2CaO SiO, Ca SiO; 3CaO 2SiO, Ca Si O and CaO SiO, CaSiO . It has a low bulk density and high physical water absorption . </P> <P> Calcium silicate is used as an anticaking agent in food preparation, including table salt and as an antacid . It is approved by the United Nations' FAO and WHO bodies as a safe food additive in a large variety of products . </P> <P> Calcium silicate is commonly used as a safe alternative to asbestos for high - temperature insulation materials . 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 and proprietary insulation solids, such as perlite mixture and vermiculite bonded with sodium silicate . Although it is popularly considered an asbestos substitute, early uses of calcium silicate for insulation still made use of asbestos fibers . </P> <P> It is used in passive fire protection and fireproofing as calcium silicate brick or in roof tiles . It is one of the most successful materials in fireproofing in Europe . Where North Americans use spray fireproofing plasters, Europeans are more likely to use cladding made of calcium silicate . High - performance calcium - silicate boards retain their excellent dimensional stability even in damp and humid conditions and can be installed at an early stage in the construction program, before wet trades are completed and the building is weather - tight . For sub-standard products, 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 . </P>

A combination of silicon hydrogen and oxygen is known as silica