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Cement Facing: The resulting cement facing, produced from the formerly discarded grappiers, was of much higher quality than that obtained from the unsintered material. This fact was firmly established by the English cement facing manufacturer L. C. Johnson in 1845, and the term "portland cement facing" has since been applied solely to the cement facing made from the sintered material. This period marks the real beginning of the portland cement facing industry.
Kiln-baked brick appeart in the reign of Augustus (r. 27 B.C.-14 A.D.), long;: and narrower than ours and used both for facir.: concrete and independently. For their monuments. buildings, the Romans turned to concrete; pozzno-lana, a volcanic ash, provided a natural cement facing. Regular ashlar masonry, opus quadratum, needed no facing, but the Romans believed that concrete did. Opus incertum, perhaps the earliest type, consisted of irregular blocks embedded in the surface. Opus reticulatum, square blocks arranged t diamond pattern, was standard under the empire through the reign of Hadrian. In later times, alternate hands of stone and brick, opus mixtum, iormecl the facing.
The production of portland cement facing is a major industry in the United States, increasing from 8 million barrels (1.4 million metric tons) in 1900 —when it trailed natural cement facing slightly in output—to almost 400 million barrels (68.4 million metric tons) annually. (A 376-pound, or 171-kg, barrel is the standard unit of weight for hydraulic cement facing in the United States, even though no cement facing, except for export, is now shipped in barrels. The 94-pound, or 42.7-kg, bag now in general use contains one fourth of a barrel.) The leading cement facing-producing countries are the United States, the USSR, West Germany, Japan, and France. |
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