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:
“A sociosphere of contact, control, persuasion and dissuasion, of exhibitions of inhibitions in massive or homeopathic doses...: this is obscenity. All structures turned inside out and exhibited, all operations rendered visible. In America this goes all the way from the bewildering network of aerial telephone and electric wires ... to the concrete multiplication of all the bodily functions in the home, the litany of ingredients on the tiniest can of food, the exhibition of income or IQ.”
—Jean Baudrillard (b. 1929)
“Beauty, like all other qualities presented to human experience, is relative; and the definition of it becomes unmeaning and useless in proportion to its abstractness. To define beauty not in the most abstract, but in the most concrete terms possible, not to find a universal formula for it, but the formula which expresses most adequately this or that special manifestation of it, is the aim of the true student of aesthetics.”
—Walter Pater (1839–1894)
“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)