This page and the linked pages below summarize the cement manufacturing process from the perspective of the individual components of a cement plant - the kiln, the cement mill etc..
For information on materials, including reactions in the kiln, see the ' Clinker ' pages. For a more detailed account of the cement production process, see the Understanding Cement book.
Cement is typically made from limestone and clay or shale. These raw materials are extracted from the quarry crushed to a very fine powder and then blended in the correct proportions.
This blended raw material is called the 'raw feed' or 'kiln feed' and is heated in a rotary kiln where it reaches a temperature of about 1400 C to 1500 C. In its simplest form, the rotary kiln is a tube up to 200 metres long and perhaps 6 metres in diameter, with a long flame at one end. The raw feed enters the kiln at the cool end and gradually passes down to the hot end, then falls out of the kiln and cools down.
The material formed in the kiln is described as 'clinker' and is typically composed of rounded nodules between 1mm and 25mm across.
After cooling, the clinker may be stored temporarily in a clinker store, or it may pass directly to the cement mill.
The cement mill grinds the clinker to a fine powder. A small amount of gypsum - a form of calcium sulfate - is normally ground up with the clinker. The gypsum controls the setting properties of the cement when water is added.
Articles like this one can provide a lot of useful material. However, reading an article or two is perhaps not the best way to get a clear picture of a complex process like cement production. You will gain a more complete and integrated understanding of how cement is made, from a cement chemistry perspective, by reading the Understanding Cement book or ebook. This easy-to-read and concise book also contains much more detail on concrete chemistry and deleterious processes in concrete compared with the website.
See the Understanding Cement Book page for more information.
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