Cement clinker

It is produced by sintering (fusing together without melting to the point of liquefaction) limestone and aluminosilicate materials such as clay during the cement kiln stage.

Some of the second raw materials used are: clay, shale, sand, iron ore, bauxite, fly ash and slag.

Portland cement clinker is made by heating a homogeneous mixture of raw materials in a rotary kiln at high temperature.

For special cements, such as low heat (LH) and sulfate resistant (SR) types, it is necessary to limit the amount of tricalcium aluminate formed.

The clinker and its hydration reactions are characterized and studied in detail by many techniques, including calorimetry, strength development, X-ray diffraction, scanning electron microscope and atomic force microscopy.

A small amount of gypsum (less than 5 wt.%) must be added to avoid the flash setting of the tricalcium aluminate (Ca3Al2O6), the most reactive mineral phase (exothermic hydration reaction) in Portland clinker.

Pulhamite can be extremely convincing and was popular in creating natural looking rock gardens in the nineteenth century.

Traditional methods for preventing desiccation involve covering the product with wet burlap or use of plastic sheeting.. For larger projects, such as highways, the surface is sprayed with a solution of curing compound that leaves a water-impermeable coating.