Calcium silicate (often referred to by its shortened trade name
Cal-Sil or
Calsil) is the chemical compound Ca
2SiO
4, also known as calcium orthosilicate and sometimes formulated 2CaO.SiO
2. It is one of group of compounds obtained by reacting
calcium oxide and
silica in various ratios
[1] e.g. 3CaO.SiO
2,
Ca3SiO5; 2CaO.SiO
2, Ca
2SiO
4; 3CaO.2SiO
2, Ca
3Si
2O
7 and CaO.SiO
2,
CaSiO3. Calcium orthosilicate is a white powder with 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, roof tiles, table salt
[2] and occurs in cements, where it is known as
belite (or in
cement chemist notation C
2S).
Calcium silicate passive fire protection board being clad around steel structure in order to achieve a fire-resistance rating.High temperature insulation
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 as well as 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.
Passive fire protectionOne 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.
Acid mine drainage remediationCalcium silicate is also a constituent of the
slag that is produced when molten
iron is made from
iron ore and
calcium carbonate in a
blast furnace. When this material is processed into a highly refined, repurposed calcium silicate aggregate, it is used in the remediation of
acid mine drainage (AMD) on active and passive mine sites.
[3] Calcium silicate neutralizes active acidity in AMD systems by removing free hydrogen ions from the bulk solution, thereby increasing
pH. As its silicate anion captures H
+ ions (raising the pH), it forms monosilicic acid (H
4SiO
4), a neutral solute. Monosilicic acid remains in the bulk solution to play other important roles in correcting the adverse effects of acidic conditions. As opposed to limestone (a popular remediation material),
[4] calcium silicate effectively precipitates heavy metals and does not armor over, prolonging its effectiveness in AMD systems.
[3][5]As a product of sealantsWhen
sodium silicate is applied as a sealant to cured
concrete or the shells of fresh
eggs, it chemically reacts with calcium hydroxide or carbonate to form calcium silicate hydrate, sealing pores with a relatively impermeable material.
References- ^ H F W Taylor, Cement Chemistry, Academic Press, 1990, ISBN 0-12-683900-X, p 33-34
- ^www.mortonsalt.com/faqs/food_salt_faq.html
- ^ abZiemkiewicz, Paul. "The Use of Steel Slag in Acid Mine Drainage Treatment and Control". Retrieved 25 April 2011.
- ^Skousen, Jeff. "Chemicals". Overview of Acid Mine Drainage Treatment with Chemicals. West Virginia University Extension Service. Retrieved 29 March 2011.
- ^Hammarstrom, Jane M.; Philip L. Sibrell; Harvey E. Belkin. "Characterization of limestone reacted with acid-mine drainage". Applied Geochemistry (18): p.1710–1714. Retrieved 30 March 2011.
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