Cement production Process involves the heating, calcining and sintering of a carefully proportioned mixture of calcareous and argillaceous materials, usually limestone and clay, to produce cement clinker, which is then cooled and ground with additives such as gypsum (a setting retardant) to make cement.

This process typically requires approximately 2.9 to 6.7 GJ of energy depending on the kiln technology employed and 1.5  to 1.7 tons of raw materials per ton of clinker produced; the portion of raw material that does not become clinker is either lost on ignition or becomes CKD.

“Wet” processes also use water to make the raw slurry that feeds the kilns; about 600 kg of water is used in the manufacture of one ton of cement, some of which is returned to the environment.

Manufacturers use clinker and specific constituents in various proportions to produce cements that meet different physical and chemical requirements for specific applications.

By far the most common hydraulic cements in use today are either Portland cements or “blended” cements.

The standard specifications with which Portland cements must comply are similar (albeit not identical) in all countries and various names are used to define the material.

Blended cements, also called composite cements, are mixtures of Portland cement with one or more pozzolanic additives or extenders (sometimes collectively termed “supplementary cementitious materials”), such as pozzolana (volcanic ashes), certain types of fly ash (from coal-fired powerplants), granulated blast furnace slag, silica fume, or limestone.

These materials commonly make up about 5 to 30 percent by weight of the total blend, but can be higher. The designations for blended cements differ worldwide.