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Sunday, 16 February 2014

Cement

Primitive people used clay as a cement to stop up holes in their sapling huts. The Assyrians and Babylonians had no better cement than this for their stone buildings.

Builders in Greek cities on the coast of Turkey (and in particular Pergamum) developed cement in about 200 BC as a structural material, in place of weaker mortars such as gypsum plaster (used in Egypt) or bitumen (in Mesopotamia).

The Romans made a cement of slaked lime and volcanic ash. This was called pozzolana after Pozzuoli, a town near Mount Vesuvius. Unlike mortar, pozzolana was a hydraulic cement, which meant it hardened under water. The Romans used it in foundations, aqueducts, and many buildings, some of which still stand.  It was the strongest mortar in history until the development of Portland cement.

The Aztec Indians in Central America used animal blood mixed with cement as a mortar for their buildings, many of which still remain standing today.

Knowledge of how to make hydraulic cement was lost during the Middle Ages. Lime mortar, however, was used in all parts of Europe.

John Smeaton (1724-1792), an English engineer, reinvented hydraulic cement in the 1750s. He had been commissioned to rebuild Eddystone lighthouse, which was subjected to wind and wave off the Cornwall coast. Smeaton made hydraulic cement of a limestone that contained considerable clay. Such a limestone is now called cement rock, and the cement made of it, natural cement. His technique became standard.

Joseph Aspdin (1779-1855) a Yorkshire bricklayer and inventor patented what he called Portland cement on October 21, 1824 by grinding and burning together a mixture of limestone and clay. He called it "portland" because concrete made from his cement looked like stone quarried on the Isle of Portland.

A pallet with Portland cement


Portland cement, is an artificial mineral substance used in building and engineering construction. This is made by heating clay and limestone in retorts to form a clinker which is then finely ground.

John Board was one of the first people to use concrete in a domestic setting when he built Castle House in 1851.

The United States imported its first European Portland cement in 1868. American manufacture of Portland cement began in the 1870s.



Putty is a cement compound of fine powdered chalk or oxide of lead mixed with linseed oil.

The Ailanthus altissima commonly known as the tree of heaven, is said to be the only tree that can grow in cement.

Each year there is one ton of cement poured for each man woman and child in the world.

China produces and consumes about 60 percent of the world’s cement — the Three Gorges Dam alone required 16 million tonnes of it.

China used more cement between 2011 and 2013 than the US did in the entire 20th century.

Source Compton's Interactive Encyclopedia © 1998 The Learning Company, Inc.

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