Conctrete

Cement is a complex material with many uses, a hydraulic binder which acts as a very sophisticated glue. Lafarge researchers are working to develop cements suited to diverse customer needs while reducing the impact of these products on the environmentThis article is about the construction material. For other uses, see Concrete (disambiguation).

Outer view of the Roman Pantheon, still the largest unreinforced solid concrete dome.[1]

A modern building: Boston City Hall (completed 1968) is constructed largely of concrete, both precast and poured in place.

Opus caementicium lying bare on a tomb near Rome. In contrast to modern concrete structures, the concrete walls of Roman buildings were covered, usually with brick or stone.

Hennebique House in Bourg-la-Reine, constructed between 1894 and 1904, the first concrete building in France.Concrete is a composite construction material, composed of cement (commonly Portland cement) and other cementitious materials such as fly ash and slag cement, aggregate (generally a coarse aggregate made of gravel or crushed rocks such as limestone, or granite, plus a fine aggregate such as sand), water and chemical admixtures.

The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

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 robust stone-like material. Concrete is used to make pavements, pipe, architectural structures, foundations, motorways/roads, bridges/overpasses, parking structures, brick/block walls, footings for gates, fences and poles and even boats.

Concrete is used more than any other man-made material in the world.[2] As of 2006, about 7.5 billion cubic metres of concrete are made each year--more than one cubic metre for every person on Earth.[3]

Concrete powers a US$35 billion industry, employing more than two million workers in the United States alone.[citation needed] More than 55,000 miles (89,000 km) of highways in the United States are paved with this material. Reinforced concrete, prestressed concrete and precast concrete are the most widely used types of concrete functional extensions in modern days.

Contents [hide]

1 History

1.1 Additives

2 Composition

2.1 Cement

2.2 Water

2.3 Aggregates

2.4 Reinforcement

2.5 Chemical admixtures

2.6 Mineral admixtures and blended cements

3 Concrete production

3.1 Mixing concrete

3.2 Workability

3.3 Curing

4 Properties

5 Environmental and health

5.1 Carbon dioxide emissions and climate change

5.2 Surface runoff

5.3 Urban heat

5.4 Concrete dust

5.5 Toxic and radioactive contamination

5.6 Handling precautions

6