Construction documents often specify a cement type based on the required performance of the concrete or the placement conditions. Certain cement manufacturing plants only produce certain types of Portland cement. What are the differences in these cement types and how are they tested, produced, and identified in practice?
In the most general sense, Portland cement is produced by heating sources of lime, iron, silica, and alumina to clinkering temperature (2,500 to 2,800 degrees Fahrenheit) in a rotating kiln, then grinding the clinker to a fine powder. The heating that occurs in the kiln transforms the raw materials into new chemical compounds. Therefore, the chemical composition of the cement is defined by the mass percentages and composition of the raw sources of lime, iron, silica, and alumina as well as the temperature and duration of heating. It is this variation in raw materials source and the plant-specific characteristics, as well as the finishing processes (i.e. grinding and possible blending with gypsum, limestone, or supplementary cementing materials), that define the cement produced.