Cement

In the most general sense of the word, a cement is a binder, a substance which sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term "opus caementicium" to describe masonry which resembled concrete and was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives which were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement. Cements used in construction are characterized as hydraulic or non-hydraulic.
The most important use of cement is the production of mortar and concrete—the bonding of natural or artificial aggregates to form a strong building material which is durable in the face of normal environmental effects.
Concrete should not be confused with cement because the term cement refers only to the dry powder substance used to bind the aggregate materials of concrete. Upon the addition of water and/or additives the cement mixture is referred to as concrete, especially if aggregates have been added.
In 2008, the world production of hydraulic cement was 1,800 million metric tons. The top three producers were China with 704, India with 100, and the United States with 91 million metric tons for a combined total of about half the world total by the world\\\'s three most populous states