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Calcium silicate can refer to several silicates of calcium including:
CaO·SiO2, wollastonite (CaSiO3)
2CaO·SiO2, larnite (Ca2SiO4)
3CaO·SiO2, alite or (Ca3SiO5)
3CaO·2SiO2, (Ca3Si2O7).
This article focuses on Ca2SiO4, also known as calcium orthosilicate, or by the shortened trade name Cal-Sil/Calsil.
All calcium silicates are white free-flowing powders.
Being strong, cheap and nontoxic, they are components of important structural materials.
Production and occurrence
Calcium silicates are produced by treating calcium oxide and silica in various ratios.
Their formation is relevant to Portland cement.
Calcium silicate is a byproduct of the Pidgeon process, a major route to magnesium metal.
The process converts a mixture of magnesium and calcium oxides as represented by the following simplified equation:
MgO·CaO +Si → 2 Mg + Ca2SiO4
The calcium oxide combines with silicon as the oxygen scavenger, yielding the very stable calcium silicate and releasing volatile (at high temperatures) magnesium metal.
Via the carbonate–silicate cycle, carbonate rocks convert into silicate rocks by metamorphism and volcanism and silicate rocks convert to carbonates by weathering and sedimentation.
The production of sulfuric acid from anhydrous calcium sulfate produces calcium silicates.
Upon being mixed with shale or marl, and roasted at 1400 °C, the sulfate liberates sulfur dioxide gas, a precursor to sulfuric acid.
The resulting calcium silicate is used in cement clinker production.
2 CaSO4 + 2 SiO2 + C → 2 CaSiO3 + 2 SO2 + CO2
Description
The Expert Panel for Cosmetic Ingredient Safety concluded that the following 24 silicate ingredients are safe in cosmetics in the present practices of use and concentration described in this safety assessment when formulated to be non-irritating, with the exception that the available data are insufficient to make a determination of safety for the use of naturally-sourced (i.e., mined) silicate ingredients in products that may be incidentally inhaled: Calcium Silicate.
Chemical Name:Calcium silicate
Molecular Formula: CaO3Si
Molecular Weight: 116.16
MDL Number: MFCD00015979
MOL File: 1344-95-2.mol
MSDS File: SDS
TDS File: TDS
Synonyms:
Calcarea silicata
Huberderm 1000
INS NO.552
INS-552
S4255P4G5M
Melting point: 1540℃ [CRC10]
Density: 2.9 g/mL at 25 °C (lit.)
solubility: Practically insoluble in water; forms a gel with mineral acids.
Calcium silicate can absorb up to 2.5 times its weight of liquids and still remain a free-flowing powder.
form: white monoclinic crystals
Specific Gravity: 2.9
color: white monoclinic crystals, crystalline
PH: 9.5-11.5 (5% in H2O)
Odor: at 100.00%. odorless
Water Solubility: insoluble H2O [HAW93]
Merck: 13,1707
Stability: Stable.
Cosmetics Ingredients Functions : ABSORBENT, BULKING, OPACIFYING
Cosmetic Ingredient Review (CIR): Calcium silicate (1344-95-2)
InChI: 1S/Ca.O3Si/c;1-4(2)3/q+2;-2
InChIKey: OYACROKNLOSFPA-UHFFFAOYSA-N
LogP: 0.651 (est)
FDA UNII: S4255P4G5M
ATC code: A02AC02
EPA Substance Registry System: Calcium silicate (1344-95-2)
UNSPSC Code: 12352301
NACRES: NA.22
Other names
Belite
Calcium monosilicate
Calcium hydrosilicate
Calcium metasilicate
Calcium orthosilicate
Micro-cell
Silene
Silicic acid calcium salt
Product
Calcium Silicate (Ca-Si) plates are asbestos-free insulating materials.
They are mainly used as back-up insulations for heavy refractory bricks or castable combinations.
Low thermal shock resistance avoids calcium silicate to be used as a working line.
They are easy to machine, without any harmful dusts for human health.
Description
Calcium Silicate is a hydrous or anhydrous silicate with varying proportions of calcium oxideand silica.
Many different calcium silicates occur in nature in mineral form (e.g.,wollastonite, afwillite, grammite).
The stoichiometry of the hydrate in cement paste is variable and the state of the chemically and physically bound water in its structure is not clear.
Thus, calcium silicate can be prepared by calcining the oxide with silica, SiO2, at an elevated temperature: CaO + SiO2+ heat→CaSiO3. Calcium orthosilicate is commonly used as a safe alternative to asbestos for high-temperature insulation materials.
Industrial grade piping and equipment insulation are often fabricated from calcium orthosilicate.
Chemical Properties
Calcium silicate occurs as a crystalline or amorphous white or off white material, and often exists in different hydrate forms.
Calcium Silicate consists of different ratios of CaO and SiO4, including tricalcium silicate (3CaO.SiO2) and dicalcium silicate Ca2SiO4.
Calcium silicate is insoluble in water and forms a gel with inorganic acids.
The pH of 5% suspension is 8.4~10.2.
Uses
Calcium Silicate is an anticaking agent that exists in different forms, which are insoluble in water.
Calcium Silicate is used in salt to enhance flowability under extremely high humidity conditions.
Calcium Silicate is also used in baking powder and fabricated chips to absorb water or other liquids.
Production Methods
Calcium silicate is made in various ways by reacting siliceous material (such as diatomaceous earth) and calcium compounds (such as calcium hydroxide (Ca (OH) 2).
The refinement of wollastonite ore into high-grade wollastonite was originally done by manual selection at many mines.
This process is now performed by screening and magnetic separators, sometimes in combination with flotation and vacuum filtration.
Grinding and milling operations can produce variable mesh powders or aggregates.
Application
The main applications of calcium silicate relate to its anticaking properties, and Calcium silicate has therefore been used in dusting powders and a range of different cosmetic products (e.g. face powders, eye shadow).
Calcium Silicate is also used as anticaking agent in table salt, foods, pharmaceuticals, and agricultural pesticides; replacement for asbestos in thermal insulation; Constituent (produced in situ) of lime glass, portland cement; reinforcing filler in elastomers and plastics; absorbent for liquids, gases, vapors; as anti-caking agent, suspension agent, pigment and pigment extender; binder for refractory material; in chromatography; in road construction.
Preparation
Calcium silicate is a naturally occurring mineral, but for commercial applications Calcium Silicate is usually prepared from lime and diatomaceous earth under carefully controlled conditions.
Hazard
Irritating dust.
Use in foods restricted to 5% in baking powder, 2% in table salt.
Upper res- piratory tract irritant.
Questionable carcinogen.
Health Hazard
The toxicity of calcium silicate depends on particle size, aspect ratio, and amount of silica and respirable fiber.
1 Synthetic nonfibrous calcium silicate is considered to be a nuisance dust.
Skin irritation was reported in a worker exposed to an atmosphere permeated with calcium silicate.
1 A study of 104 wallastonite (a naturally occurring calcium silicate mineral) miners showed no relationship between the prevalence of chronic bronchitis or airflow obstruction with increasing exposure.
1 In a cohort mortality study of wollastonite quarry workers the observed numbers of deaths from all cancers combined and lung cancer were lower than expected.
Flammability and Explosibility
Not classified
Pharmaceutical Applications
Calcium silicate (Ca2SiO4) is used in the pharmaceutical industry as an anticaking agent.
Anti-caking agents absorb moisture and allow products to flow freely during the manufacturing process.
Calcium silicate is also used as a filler aid for oral pharmaceuticals.
Calcium Silicate has also been used in pharmaceutical preparations as an antacid.
Industrial uses
Calcium silicate compounds belong to a complicated class of silicates.
Among their many industrial applications, calcium silicates are heavily used as a building material as they constitute the main ingredient in today’s cement clinker.
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.
Calcium Silicate İs 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 Calcium Silicate is popularly considered an asbestos substitute, early uses of calcium silicate for insulation still made use of asbestos fibers.
Passive fire protection
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.
Calcium Silicate is used in passive fire protection and fireproofing as calcium silicate brick or in roof tiles.
Calcium Silicate is one of the most successful materials in fireproofing in Europe because of regulations and fire safety guidelines for commercial and residential building codes.
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.
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.
Acid mine drainage remediation
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, Calcium silicate is used in the remediation of acid mine drainage (AMD) on active and passive mine sites.
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), Calcium silicate 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),calcium silicate effectively precipitates heavy metals and does not armor over, prolonging its effectiveness in AMD systems.
As a product of sealants
Calcium silicate 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, Calcium silicate chemically reacts with calcium hydroxide or calcium carbonate to form calcium silicate hydrate, sealing micropores with a relatively impermeable material.
