Calcium silicate is an inorganic chemical compound, calcium salt of silicic acid, containing Si, Ca, O. It is produced by the reaction between CaO and silica. 

It appears as a white powder.

What it is used for and where

Food

Ingredient included in the list of European food additives as E552 with anti-caking and anti-acid functions.

Cosmetics

Absorbent. Absorbs substances dispersed or dissolved in aqueous solutions, water/oil, oil/water.

Bulking agent. It regulates the water content, dilutes other solids, can increase the volume of a product for better flow, acts as a buffer against organic acids, helps to keep the pH of the mixture within a certain level.

Opacifying agent. It is useful into formulations that may be translucent or transparent to make them opaque and less permeable to light.

Pearlescent.

Viscosity control agent. It controls and adapts viscosity to the required level for optimal chemical and physical stability of the product and dosage in gels, suspensions, emulsions, solutions. 

Medical

Calcium silicate represents a biomaterial for bone repair due to good degradability and bioactivity (1), used for pH-sensitive drug delivery (2) , common implant material with excellent mechanical strength and good biological activity.

Safety

EFSA's Panel on Food Additives provided a scientific opinion on the safety of calcium silicate (E552), magnesium silicate (E553a) and talc (E553b) when used as food additives. The Panel noted that the absorption of silicates and talc was very low; there was no indication of genotoxicity or developmental toxicity of calcium and magnesium silicates and talc, and no confirmed cases of renal effects were found in the EudraVigilance database, despite the extensive and long-term use of high doses of magnesium trisilicate up to 4 g/person/day for decades. However, the Panel considered that an accumulation of silicon from calcium silicate in the kidney and liver was reported in rats and that reliable data on the subchronic and chronic toxicity, carcinogenicity and reproductive toxicity of silicates and talc were lacking. Therefore, the Panel concluded that the safety of calcium silicate (E552), magnesium silicate (E553a(i)), magnesium trisilicate (E553a(ii)) and talc (E553b) when used as food additives cannot be evaluated. (3)

Other uses

• critical material for refractories, glass, paints
• adsorbent of heavy metal cations 
• used as a porous material to absorb nitrate PCM
• removal of copper from aqueous solutions
• useful carrier for the development of floating and sustained-release preparations

• Molecular Formula    Ca₂O₄Si  
• Molecular Weight      
• CAS  1344-95-2
• UNII    9W3UX8K5UQ
• EC Number   215-710-8 

References_____________________________________________________________________

(1) Xia, W. and Chang, J., 2008. Preparation and the phase transformation behavior of amorphous mesoporous calcium silicate. Microporous and mesoporous materials, 108(1-3), pp.345-351.

(2) Wang, D., Han, S. and Lu, B.B., 2021. Biocompatible Eu doped mesoporous calcium silicate nanospheres for pH-responsive drug release. Inorganic Chemistry Communications, 133, p.108872.

(3) EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS), Younes, M., Aggett, P., Aguilar, F., Crebelli, R., Dusemund, B., Filipič, M., Frutos, M.J., Galtier, P., Gott, D. and Gundert‐Remy, U., 2018. Re‐evaluation of calcium silicate (E 552), magnesium silicate (E 553a (i)), magnesium trisilicate (E 553a (ii)) and talc (E 553b) as food additives. EFSA Journal, 16(8), p.e05375.