Calcium

Limestone has been used for tens of thousands of years. Crushed limestone was already used as a pigment (white chalk) in prehistoric cave paintings. Lime mortar was used in constructions as early as 10.000 BC in Mesopotamia and in ancient Egypt. The outer walls of the Great Pyramid of Giza (around 2600 BC) were made of Tura limestone. The ancient Romans used lime concrete in the construction of the Pantheon.

The name “Calcium” is derived from the Latin word calx. The Romans used this term to denote lime, limestone, chalk, and mortar made from lime.

The silvery, relatively soft and light metal was first isolated in 1808 by Sir Humphry Davy, after he distilled mercury from an amalgam produced by the electrolysis of a mixture of lime and mercury oxide.

The most commonly used calcium compound across various industries is calcium carbonate, also known as limestone, which is inexpensive and versatile.

It is the main component of the most important building materials: cement, mortar, and concrete. Calcium carbonate is used in the paper industry as a filler or coating to achieve smoothness and brightness. In agriculture, limestone is used to improve acidic soils.

Calcium oxide, also known as quicklime, is produced by heating the raw material calcium carbonate. Calcium oxide is used in steel production, water treatment, and chemical manufacturing.

Calcium hydroxide (slaked lime) is used in wastewater treatment, leather tanning, and mortar production.

Calcium sulfate (gypsum or plaster) is another application in the building materials industry. Calcium chloride is used in road de-icing agents, food preservatives, concrete accelerators, and drying agents.

Pure calcium metal is used as an alloying element for aluminum, copper, lead, magnesium, and other base metals, as a deoxidizer for certain high-temperature alloys, and as a getter in vacuum tubes.

The production volumes of calcium metal are relatively low compared to other metals, ranging from 10.000 to 20.000 tons annually.

Calcium is a very abundant element in the Earth’s crust and occurs in numerous minerals, many of which are economically significant.

The most common sources of calcium are carbonate minerals such as calcite, found in limestone, marble, and chalk. Calcium is also present in sulfate minerals like gypsum and anhydrite, in phosphate minerals such as apatite, and in silicate minerals including wollastonite, plagioclase feldspar, and grossular.

The main producing countries of calcium metal are China, Russia, France, and the USA.

Limestone (calcium carbonate) is a substitute for lime (calcium oxide) in many applications, such as agriculture, flux production, and sulfur removal. Limestone contains fewer reactive substances, reacts more slowly, and may have additional disadvantages compared to lime depending on the application. However, limestone is significantly cheaper than lime.

Calcined gypsum is an alternative material for industrial plasters and mortars.

Cement, cement kiln dust, fly ash, and lime kiln dust are potential substitutes for some construction applications of lime.

Magnesium hydroxide is a substitute for lime in pH regulation, and magnesium oxide is a substitute for dolomitic lime as a flux in steel production.