Cement is a complex mix of many [chemical compounds]. Of these, the principal four are:

[tricalcium silicate] (3CaO.SiO2) also known as [Alite]
[dicalcium silicate] (2CaO.SiO2) also known as [Belite]
[tricalcium aluminate] (3CaO.Al2O3), and
a [ferrite phase] from the (2CaO.Fe2O3 - 6CaO.2Al2O3.Fe2O3) solid solution series that at one time was considered to have the fixed composition (4CaO.Al2O3.Fe2O3)

Alite is the compound that gives cement its immediate strengthening property, whereas belite provides [material strength] over longer periods of time.

These compounds are obtained by a process known as [clinkerization], which involves heating a mix of [calcium oxide] (CaO), [silicon oxide] (Si2O2), [aluminum oxide] (Al2O3) and [ferric oxide] (Fe2O3) at temperatures over 1400 [Celsius] to produce [clinker], the main ingredient of cement.

The four [oxides] required to supply the clinkerization process can be obtained by raw materials like [limestone], [schist], [clay], [dolomite], [silica sand], [bauxite], [wet fly ash] and [iron ore]. These are obtained by quarrying. Silica oxide, aluminum oxide and ferric oxide are readily found in their respective raw materials, but calcium oxide must be extracted from [calcium carbonate] (CaCO3) found in limestone. This is achieved by a process known as [calcination], which absorbs heat energy and releases calcium carbonate and [carbon dioxide] (CO2). Calcination occurs in a production stage before clinkerization, where the [raw materials], having being mixed an milled into powder are being preheated to gradually reach [kiln] temperatures.

Clinker, which is produced in the form of [sintered lumps], is then mixed with a small proportion of [gypsum] and milled into powder to produce cement. The addition of gypsum slows down cement’s [hydration] process to make it workable in construction, but does not alter cement’s base chemical properties. In some occasions the mix is diluted with clinker substitutes such as [pozzolana] to produce cement types with inferior chemical characteristics.

Cement (thing)