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| Автор | английский язык |
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Concrete has been used for construction in various ancient civilizations. An analysis of ancient Egyptian pyramids have shown that concrete was employed in their construction.
During the Roman Empire, Roman concrete (or Opus caementicium) was made from quicklime, pozzolanic ash/pozzolana, and an aggregate of pumice. Its widespread use in many Roman structures, a key event in the history of architecture termed the Concrete Revolution, freed Roman construction from the restrictions of stone and brick material and allowed for revolutionary new designs both in terms of structural complexity and dimension.
Concrete, as the Romans knew it, was in effect a new and revolutionary material. Laid in the shape of arches, vaults and domes, it quickly hardened into a rigid mass, free from many of the internal thrusts and strains which trouble the builders of similar structures in stone or brick.
Modern tests show Opus caementicium to be as strong as modern Portland cement concrete in its compressive strength (ca. 200 kg/cm2). However, due to the absence of steel reinforcement, its tensile strength was far lower and its mode of application was also different:
Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble. Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon the strength of the concrete bonding to resist tension.
нужно найти неличные формы и интернациональные слова | | удачи) | нужно найти неличные формы и интернациональные слова
фигня!мне надо всего лишь 0,5 водки и я найду тебе тут чё угодно!абсолютно)) | | Надо - ну так найди:) | нужно найти неличные формы и интернациональные слова
мне, например, ненужно) | знаешь а форумчане тут причём?
крой тему а то флудеры набегут щас | | тема закрыта by Герцогиня (2011-11-30 17:21:14) |
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