Clinker consists of various calcium silicates including alite and belite. Tricalcium aluminate and calcium aluminoferrite are other common components. These components are often generated in situ by heating various clays and limestone.
Portland cement clinker is made by heating a homogeneous mixture of raw materials in a rotary kiln at high temperature. The products of the chemical reaction aggregate together at their sintering temperature, about 1,450 C (2,640 F). Aluminum oxide and iron oxide are present only as a flux to reduce the sintering temperature and contribute little to the cement strength. 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 major raw material for the clinker-making is usually limestone mixed with a second material containing clay as source of alumino-silicate. Normally, an impure limestone which contains clay or silicon dioxide (SiO2) is used.
The calcium carbonate (CaCO3) content of these limestones can be as low as 80%. Second raw materials (materials in the rawmix other than limestone) depend on the purity of the limestone. Some of the second raw materials used are: clay, shale, sand, iron ore, bauxite, fly ash and slag. The clinker surface and its reactions in different electrolytic solutions are investigated by scanning electron microscope and atomic force microscopy.
Portland cement clinker is ground to a fine powder and used as the binder in many cement products. A little gypsum is sometimes added. It may also be combined with other active ingredients or chemical admixtures to produce other types of cement including: ground granulated blast furnace slag cement.
Clinker is a nodular material produced in the kilning stage during the production of cement and is used as the binder in many cement products. The lumps or nodules of clinker are usually of diameter 3-25 mm and dark grey in color. It is produced by heating limestone and clay to the point of liquefaction at about 1400�°C-1500�°C in the rotary kiln. Clinker, when added with gypsum (to control the setting properties of cement and ensure compressive strength) and ground finely, produces cement. Clinker can be stored for long periods of time in a dry condition without degradation of quality, hence it is traded internationally and used by cement manufacturers when raw materials are found to be scarce or unavailable.
Cement clinker is the intermediate product produced during the cement manufacturing process. It consists of finely ground materials, such as limestone, clay, iron ore, and shale, heated to high temperatures in a kiln. Clinker forms the basis of various types of cement when combined with gypsum and other additives
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