Concrete
concept is considered concrete if it is not abstract: it must be both particular and an individual, and hence occupy both space and time. To say that a physical object is concrete is to say, approximately, that it is a particular individual that is located at a particular place and time.
See particular; individual; abstract.
In construction, concrete is a composite building material made from the combination of aggregate and cement binder. The most common form of concrete is portland cement concrete, which consists of mineral aggregate (generally gravel and sand), portland cement and water.
After mixing, the cement hydrates and eventually hardens into a stone-like material. When used in the generic sense, this is the material referred to by the term concrete.
The Assyrians and Babylonians used clay as cement in their concretes. The Egyptians used lime and gypsum cement. In the Roman Empire cements made from pozzolanic ash were used to make a concrete very similar to modern portland cement concrete. In 1756, British engineer John Smeaton pioneered the use of portland cement in concrete, and used pebbles and powdered brick as aggregate.
Concrete has great compressive strength, but little tensile strength. To overcome this limitation, concrete is most often constructed with the addition of steel reinforcement bars (rebars), steel mesh, or cables, to produce reinforced concrete. Concrete can also be prestressed, which is allows for beams or slabs with a longer span than is practical with reinforced concrete.
Concrete is also made with asphalt or epoxy as a binder.
See also: Building construction
There is a comic book series, Concrete, by
