Concrete is a composite construction material composed primarily of aggregate, cement, and water. There are many formulations, which provide varied properties. The aggregate is generally a coarse gravel or crushed rocks such as limestone, or granite, along with a fine aggregate such as sand. The cement, commonly Portland cement, and other cementitious materials such as fly ash and slag cement, serve as a binder for the aggregate. Various chemical admixtures are also added to achieve varied properties. Water is then mixed with this dry composite, which enables it to be shaped (typically poured) and then solidified and hardened into rock-hard strength through a chemical process called hydration. The water reacts with the cement, which bonds the other components together, eventually creating a robust stone-like material. Concrete has relatively high compressive strength, but much lower tensile strength. For this reason it is usually reinforced with materials that are strong in tension (often steel). Concrete can be damaged by many processes, such as the freezing of trapped water.
Concrete is widely used for making architectural structures, foundations, brick/block walls, pavements, bridges/overpasses, motorways/roads, runways, parking structures, dams, pools/reservoirs, pipes, footings for gates, fences and poles and even boats. Famous concrete structures include the Burj Khalifa (world's tallest building), the Hoover Dam, the Panama Canal and the Roman Pantheon.
Concrete technology was known by the Ancient Romans and was widely used within the Roman Empire—the Colosseum is largely built of concrete. After the Empire passed, use of concrete became scarce until the technology was re-pioneered in the mid-18th century.
The environmental impact of concrete is a complex mixture of not entirely negative effects; while concrete is a major contributor to greenhouse gas emissions, recycling of concrete is increasingly common in structures that have reached the end of their life. Structures made of concrete can have a long service life. As concrete has a high thermal mass and very low permeability, it can make for energy efficient housing.
Other articles related to "concrete":
... Approximately 6,650 tons of structural steel, 80,000 cubic yards of concrete, and 7000 cubic tons of reinforcing steel bars went into its construction ... The complex sits on a series of reinforced concrete grade beams tied to 150 concrete caissons as much as ten feet in diameter and to a depth of 80 feet ... The exterior columns and beams are concrete encased steel wide flanges surrounded by reinforcing bars ...
... Carbonatation is a slow process that occurs in concrete where lime (calcium hydroxide) in the cement reacts with carbon dioxide from the air and forms calcium carbonate ... The water in the pores of Portland cement concrete is normally alkaline with a pH in the range of 12.5 to 13.5 ... Carbon dioxide will start to carbonatate the cement in the concrete from the moment the object is made ...
... Concrete concepts have perceptible attributes they can be physically seen or proven ... Concrete concepts are usually easier for a child to understand ... death to a child can be difficult because it is hard to change it into a concrete concept ...
... There were 300 households out of which 37.0% had children under the age of 18 living with them, 45.3% were married couples living together, 14.3% had a female householder with no husband present, and 33.7% were non-families. 27.7% of all households were made up of individuals and 11.7% had someone living alone who was 65 years of age or older ...
... Culverts may be made of concrete, galvanized steel, aluminum, or plastic, typically high density polyethylene ... For example, open-bottom corrugated steel structures are often built on concrete footings, or corrugated ... Plastic culvert liners are also inserted into failing concrete or steel structures in order to repair the structure without excavating and closing the road ...
Famous quotes containing the word concrete:
“The clock of communism has stopped striking. But its concrete building has not yet come crashing down. For that reason, instead of freeing ourselves, we must try to save ourselves from being crushed by its rubble.”
—Alexander Solzhenitsyn (b. 1918)
“Poetry presents indivisible wholes of human consciousness, modified and ordered by the stringent requirements of form. Prose, aiming at a definite and concrete goal, generally suppresses everything inessential to its purpose; poetry, existing only to exhibit itself as an aesthetic object, aims only at completeness and perfection of form.”
—Richard Harter Fogle, U.S. critic, educator. The Imagery of Keats and Shelley, ch. 1, University of North Carolina Press (1949)
“The Dada object reflected an ironic posture before the consecrated forms of art. The surrealist object differs significantly in this respect. It stands for a mysterious relationship with the outer world established by mans sensibility in a way that involves concrete forms in projecting the artists inner model.”
—J.H. Matthews. Object Lessons, The Imagery of Surrealism, Syracuse University Press (1977)