Concrete
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.
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Famous quotes containing the word concrete:
“In his comprehensive delight in all experience Dickens resembles Walt Whitman, but he was innocent of that nebulous transcendentalism that blurred Whitman’s universe into vast misty panoramas and left him, for all his huge democratic vistas, unable to tell a story or paint a single concrete human being.”
—Edgar Johnson (1912–1990)
“To step over the low wall that divides
Road from concrete walk above the shore
Brings sharply back something known long before
The miniature gaiety of seasides.”
—Philip Larkin (1922–1986)
““The city’s grotesque iron skeletons
Would knock their drunken penthouse heads together
And cake their concrete dirt off in the streets.””
—Robert Frost (1874–1963)