by Introduction
Calcium sulphate, also known as gypsum, is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO4·2H2O. It is widely found in nature and used in a variety of applications. In this article, we will explore the properties, uses and importance of calcium sulphate in different industries.
Chemical Properties and Forms
Calcium sulphate exists in two main chemical forms – the dihydrate (CaSO4·2H2O) and the hemihydrate (CaSO4·0.5H2O). The dihydrate, which is hydrated calcium sulfate, is stable below 32°C while hemihydrate is stable above that temperature. Anhydrite refers to the anhydrous form without water (CaSO4).
Calcium sulphate is odorless and almost tasteless. It is colorless to white in powdered form and transparent to opaquely white as a single crystal. Chemically, it is only slightly soluble in water but readily soluble in acids and hydrochloric acid. It has a Mohs hardness of 2 and a specific gravity of 2.3.
Uses in Construction
As one of the most abundant minerals, calcium sulphate finds its major use in construction industries. Gypsum, the general commercial term, is used to produce building plaster, partitions and wallboards.
Manufacture of Plaster of Paris: When hydrated calcium sulfate hemihydrate is mixed with just the right amount of water, it sets into a solid material known as plaster of Paris. This is used for decorative plasterwork, making of casts and molds due to its quick setting property.
Wallboard Production: Calcium Sulphate is the primary constituent of wallboard, the most durable and impact-resistant interior wall and ceiling material. It provides strength, sound insulation and fire resistance to buildings.
Cement Manufacturing: A small amount of gypsum is added to Portland cement as an additive to retard its setting time which allows accurate handling and placing of concrete.
Other Uses in Construction
Some other applications of calcium sulphate in construction include use in repairing of cracks/holes, making of ornamental works, and manufacture of ready-mix putty for exterior paints. It is also used in soil conditioning and stabilization to improve soil permeability.
Uses in Agriculture
With excellent ability to enrich soil devoid of sulphur, gypsum finds widespread usage in agriculture as well. Here are some of the key applications:
Soil Amendment: It is used to alter the physical and chemical properties of clay soils by making them loose, friable and well-aerated to allow deep root penetration of plants.
Fertilizer: Being a good source of readily soluble calcium and sulphur, gypsum acts as a fertilizer for crops requiring these nutrients like fruits, vegetables and cereals.
Soil Reclamation: It helps reclaim saline-alkali soils by replacing sodium ions with calcium ions, thus improving soil structure and quality.
Reducing Soil Crusting: Gypsum works to decrease formation of surface soil crust which inhibits seedling emergence and erosion.
Other Industrial Uses
Calcium sulphate also has numerous applications in other industries like manufacture of glass, abrasives, food additives and chemicals. Some of these uses are:
– Manufacture of wallboard joint compounds, adhesives and caulks.
– Production of glass – supplies calcium to glass formulation and acts as a fining agent.
– Used as a retarder in Portland cement and an additive in toothpaste.
– Enters into the making of pharmaceutical drugs and food supplements.
– Manufacture of abrasives like blackboard chalk and silver sand for woodworking.
– Important coagulant used in production of paper, sugar and textiles.
– Intermediate in the synthesis of plastics, detergents and various calcium chemicals.
Calcium sulphate is truly a versatile mineral widely utilized across many domains owing to its diverse properties. From construction to agriculture to manufacturing industries, it continues to play a vital role. With several applications and importance, gypsum is all set to remain a predominant mineral resource for the future as well.
