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:
“Reality is a question of perspective; the further you get from the past, the more concrete and plausible it seems—but as you approach the present, it inevitably seems incredible.”
—Salman Rushdie (b. 1948)
“Babies are necessary to grown-ups. A new baby is like the beginning of all things—wonder, hope, a dream of possibilities. In a world that is cutting down its trees to build highways, losing its earth to concrete ... babies are almost the only remaining link with nature, with the natural world of living things from which we spring.”
—Eda Le Shan (b. 1922)
“We are all hungry and thirsty for concrete images. Abstract art will have been good for one thing: to restore its exact virginity to figurative art.”
—Salvador Dali (1904–1989)