Calcium silicate

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Calcium silicate
Names
Preferred IUPAC name
Calcium silicate
Systematic IUPAC name
Dicalcium silicate
Other names
Belite

Calcium monosilicate
Calcium hydrosilicate
Calcium metasilicate, Calcium orthosilicate
Grammite
Micro-cell
Silene

Silicic acid calcium salt
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.014.282
EC Number 235-336-9
E number E552 (acidity regulators, ...)
KEGG
MeSH Calcium+silicate
UNII
Properties
Ca2O4Si
Molar mass 172.24 g·mol−1
Appearance White crystals
Density 0.29 g/cm3 (solid)[1]
Melting point 1,540 °C (2,800 °F; 1,810 K)
0.01% (20 °C)[1]
Thermochemistry
84 J·mol−1·K−1[2]
−1630 kJ·mol−1[2]
Pharmacology
A02AC02 (WHO)
Hazards
Main hazards Irritant
Safety data sheet [3]
NFPA 704
Flammability code 0: Will not burn. E.g., water Health code 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g., chloroform Reactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogen Special hazards (white): no codeNFPA 704 four-colored diamond
Flash point Not applicable
US health exposure limits (NIOSH):
PEL (Permissible)
TWA 15 mg/m3 (total) TWA 5 mg/m3 (resp)[1]
REL (Recommended)
TWA 10 mg/m3 (total) TWA 5 mg/m3 (resp)[1]
IDLH (Immediate danger)
N.D.[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YesYN ?)
Infobox references

Calcium silicate is the chemical compound Ca2SiO4, also known as calcium orthosilicate and is sometimes formulated as 2CaO.SiO2.[citation needed] It is also referred to by the shortened trade name Cal-Sil or Calsil.

Properties[edit]

Calcium silicate is a white free-flowing powder. It can be derived from naturally occurring limestone and diatomaceous earth a siliceous sedimentary rock.[citation needed] It is one of a group of compounds which can be produced by reacting calcium oxide and silica in various ratios[4] e.g. 3CaO•SiO2, Ca3SiO5; 2CaO•SiO2, Ca2SiO4; 3CaO•2SiO2, Ca3Si2O7 and CaO•SiO2, CaSiO3. It has a low bulk density and high physical water absorption.[citation needed]

Use[edit]

Calcium silicate is used as an anticaking agent in food preparation, including table salt[5] 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.[6]

High temperature insulation[edit]

Calcium silicate passive fire protection board being clad around steel structure in order to achieve a fire-resistance rating.

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 protection[edit]

Circuit integrity fireproofing of cable trays in Lingen/Ems, Germany using calcium silicate board system qualified to DIN 4102. Other methods for exterior protection of electrical circuits include boards made of sodium silicate bonded and pressed vermiculite and flexible wraps made of ceramic fibre and rockwool.

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.[why?] 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.[citation needed]

While the best possible Reaction to Fire Classifications are A1 (construction applications) and A1Fl (flooring applications) respectively, both of which mean "non-combustible" according to EN 13501-1: 2007, as classified by a notified laboratory in Europe, some calcium silicate boards only come with Fire Classification of A2 (limited combustibility) or even lower classifications (or no classification), if they are tested at all.[citation needed]

Acid mine drainage remediation[edit]

Calcium silicate, also known as slag, is produced when molten iron is made from iron ore, silicon dioxide and calcium carbonate in a blast furnace. When this material is processed into a highly refined, re-purposed calcium silicate aggregate, it is used in the remediation of acid mine drainage (AMD) on active and passive mine sites.[7] 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 (H4SiO4), 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),[8] calcium silicate effectively precipitates heavy metals and does not armor over, prolonging its effectiveness in AMD systems.[7][9]

As a product of sealants[edit]

It is used as a sealant in roads or on the shells of fresh eggs: when sodium silicate is applied as a sealant to cured concrete or egg shells, it chemically reacts with calcium hydroxide or calcium carbonate to form calcium silicate hydrate, sealing micropores with a relatively impermeable material.[citation needed]

As a component of cement[edit]

It also occurs in cements, where it is known as belite or in cement chemist notation C2S.[citation needed]

See also[edit]

References[edit]

  1. ^ a b c d e "NIOSH Pocket Guide to Chemical Hazards #0094". National Institute for Occupational Safety and Health (NIOSH). 
  2. ^ a b Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A21. ISBN 0-618-94690-X. 
  3. ^ "SDS Sheet Library". BNZ Materials. Retrieved 2017-07-19. 
  4. ^ H F W Taylor, Cement Chemistry, Academic Press, 1990, ISBN 0-12-683900-X, p 33-34
  5. ^ [1][dead link]
  6. ^ "Food Additive Details: Calcium silicate". Archived from the original on June 5, 2012. Retrieved July 28, 2013.  Codex General Standard for Food Additives (GSFA) Online Database, FAO/WHO Food Standards Codex alimentarius, published by the Food and Agricultural Organization of the United Nations / World Health Organization, 2013.
  7. ^ a b Ziemkiewicz, Paul. "The Use of Steel Slag in Acid Mine Drainage Treatment and Control". Wvmdtaskforce.com. Retrieved 25 April 2011. 
  8. ^ Skousen, Jeff. "Chemicals". Overview of Acid Mine Drainage Treatment with Chemicals. West Virginia University Extension Service. Retrieved 29 March 2011. 
  9. ^ Hammarstrom, Jane M.; Philip L. Sibrell; Harvey E. Belkin. "Characterization of limestone reacted with acid-mine drainage" (PDF). Applied Geochemistry (18): 1710–1714. Retrieved 30 March 2011.