Definition (Source: Wikipedia)
***Concrete is a construction material that consists 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 or manufactured sand and water) and chemical admixtures.
Concrete solidifies and hardens after mixing 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. It is used to make pavements, architectural structures, foundations, motorways/roads, overpasses, parking structures, brick/block walls and footings for gates, fences and poles.
Concrete is used more than any other man-made material on the planet.[1] As of 2005 about six billion cubic meters of concrete are made each year, which equals 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 freeways and highways in America are made of this material. The People's Republic of China currently consumes 40% of the world's cement [concrete] production.