Concrete is a construction material composed of cement (commonly Portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate such as gravel limestone or granite, plus a fine aggregate such as sand), water, and chemical admixtures. The word concrete comes from the Latin word "concretus", which means "hardened" or "hard".

Concrete solidifies and hardens after mixing with water and placement due to a chemical process known as hydration. The water reacts with the cement, which bonds the other components together, eventually creating a stone-like material. The reactions are highly exothermic and care must be taken that the build-up in heat does not affect the integrity of the structure. Concrete is used to make pavements, architectural structures, foundations, roads, bridges/overpasses, parking structures, brick/block walls and footings for gates, fences and poles.

More concrete is used than any other man-made material in the world. As of 2006, about seven billion cubic meters of concrete are made each year—more than one cubic meter for every person on Earth. Concrete powers a $US 35-billion industry which employs more than two million workers in the United States alone. More than 55,000 miles of highways in America are paved with this material. The People's Republic of China currently consumes 40% of the world's cement/concrete production.

Concrete. (2008, July 11). In Wikipedia, The Free Encyclopedia. Retrieved 20:32, July 11, 2008, from http://en.wikipedia.org/w/index.php?title=Concrete&oldid=225061243