In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. Cement is made by heating limestone with small quantities of other materials to 1450 °C in a kiln, in a process known as calcination to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix. The resulting substance is then ground to make “Portland Cement”. Portland cement is a basic ingredient of concrete, mortar and most non-specialty grout. The most common use for Portland cement is in the production of concrete. In response to a federal court ruling and data from industry, the U.S. Environmental Protection Agency (EPA) is proposing changes to its 2010 air standards for the Portland cement manufacturing industry. The proposal would continue the significant emission reductions from the 2010 standards while providing industry additional compliance flexibilities, including more time to implement the proposed updates by extending the compliance date for existing cement kilns from September 2013 to September 2015.
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