Calcium carbonate, or CaCO3 is commonly found as calcite or aragonite. It is the primary component of naturally formed pearls and the shells of organisms such as snails and oysters. Industrially, pure ground calcium carbonate or ‘GCC’ is obtained through the mining of chalk, marble or limestone reserves. While chalk is a fine, crystalline material, the CaCO3 obtained from chalk is more compact. CaCO3 obtained from marble reserves is coarse and crystalline. Calcium carbonate can also be chemically prepared from calcium oxide or ‘quicklime’ using water and carbon dioxide. The calcium carbonate produced in this manner is known as precipitated calcium carbonate or PCC, and it has a controlled, extremely fine particle size.
China, India, the U.S.A and Europe are leading producers of limestone, with China producing nearly 54% of the global throughput. Leading producers of marble in the current markets include Turkey, Italy, Greece and Iran.
Calcium carbonate can be considered as a ‘jack of all trades’ chemical because of its diverse uses in a range of industries, including the construction, paper and healthcare industry.
Calcium carbonate finds its primary use in the construction industry as a starting material for building materials like cement or builder’s lime. Limestone aggregate is also the primary constituent of concrete and is widely used in road construction. When mixed with soil, calcium carbonate helps to transfer cement-like properties to the soil, enabling the foundations of buildings to be firmer and allowing construction vehicles to easily traverse the construction paths. Owing to its ability to be degraded by acid rain, calcium carbonate is never used as the sole component for brick or building material construction, but it is still highly important as a starting material due to its rigidity and stability.
Approximately 3.6 billion tonnes of cement are produced per year, and since cement consists limestone aggregate and various clays in a 1:1 ratio, roughly 1.8 billion tonnes of limestone would need to be produced per year, attesting to the great importance of calcium carbonate in the construction industry.
In the paper industry, calcium carbonate is widely used as a filler for paper production. Owing to its low prices and optimal particle size, it is preferred to wood fibres as a non-polluting filler in the production of paper. It is currently being used instead of kaolin for the production of glossy paper. The PCC produced can even be coated with several other materials to ensure porosity and guarantee whiteness to the paper produced.
Healthcare and Food Industry
In the healthcare industry, calcium carbonate is used medicinally as a calcium supplement in antacid production. It is a major component in various commercial antacids such as ‘Tums’ etc. It is also used as an inert filler for tablets and other pharmaceutical products.
Aside from its use in the manufacture of drugs, calcium carbonate is also used as a food additive under the designated code E170. It can be used commercially as an acidity regulator, anticaking agent and as a stabilizer. It can also be used as a non-toxic source of calcium in vegan products such as soy milk and almond milk. Additionally, calcium carbonate is used in several canned or bottled vegetable products as a firming agent.