What Is Calcium Silicate?
Calcium silicate is a compound formed from calcium and silicate. It consists of more than 20 different compounds due to variations in the composition of its constituent elements. The most common types include ortho-calcium silicate, tricalcium silicate, and meta-calcium silicate, often referred to simply as calcium silicate.
This compound can be synthesized by reacting calcium oxide with silicon dioxide (from limestone and diatomaceous earth) at high temperatures. Calcium Silicate is safe for health and approved for use as a food additive.
Uses of Calcium Silicate
Calcium silicate serves as an effective building material, appreciated for its lightweight, thermal insulation, non-combustibility, and fire resistance. In agriculture, it finds extensive use as a fertilizer component.
In the ceramics industry, it prevents shrinkage, gas generation, and cracking when added during firing. It enhances the tensile strength, stiffness, and heat resistance of rubber and durability of paints as an additive. Additionally, it acts as an anti-caking agent in food products, such as baking powder and salt.
Properties of Calcium Silicate
Upon heating, calcium silicate hydrates release water, slowing the material’s temperature rise due to the heat of vaporization. It is noncombustible and has refractory properties.
Structure of Calcium Silicate
Calcium silicate, a type of silicate, comprises silicon dioxide, calcium oxide, and water in various ratios. Its microstructure features numerous voids, contributing to its lightweight, heat-retaining, and insulating properties.
Other Information on Calcium Silicate
Chemical Composition Variants of Calcium Silicate
Beyond the common types such as ortho-calcium silicate (Ca2SiO4), tricalcium silicate (Ca3SiO5), and meta-calcium silicate (CaSiO3)n, numerous calcium silicate variants exist with varied chemical compositions.
Examples include 3CaO·SiO2 (Ca3SiO5), 2CaO·SiO2 (Ca2SiO4), 3CaO·2SiO2 (Ca3Si2O7), CaO·SiO2, and CaSiO3.
1. Ortho-Calcium Silicate
Ortho-calcium silicate, a major component of cement clinker (10-40%), is also known in the cement industry as dicalcium silicate or belite. Its chemical formula is Ca2SiO4, with a molecular weight of 172.24, consisting of tetrahedral SiO4 structures.
2. Tricalcium Silicate
Tricalcium silicate, with the chemical formula Ca3SiO5 and a molecular weight of 228.32, contains tetrahedral SiO4 and oxygen in its solid form. It is a primary component of cement clinker, comprising 40-70% of its makeup, and is referred to as tricalcium silicate in the cement industry.
3. Meta-Calcium Silicate
Meta-calcium silicate, or calcium metasilicate, has the formula (CaSiO3)n and a molecular weight of 116.16 x n. It exists in two phases: the β-phase, known as wollastonite and stable at room temperature, with a density of 2.9 g/cm3, and the α-phase, known as pseudowollastonite.