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Sunday, 22 June 2014

Concrete

The ancient Romans had concrete at least as early as 200 BC making it with pozzolana, a volcanic ash from Mount Vesuvius, near Pozzuoli, Italy. Pozzolana is still used today.

Pozzolana concrete was at first used it only for terrace walls and foundations, as, for example, at the Temple of Fortuna Primigenia at Palestrina, erected about 80 BC.

It was the emperor Nero who first used the material on a grand scale to rebuild a region of the city of Rome around his palace, the expansive Domus Aurea (Golden House), after the great fire of AD 64.

Roman concrete was a fluid mixture of lime and small stones poured into the hollow centers of walls faced with brick or stone and over curved wooden molds, or forms, to span spaces as vaults.

The development of concrete used in conjunction with brick, along with a great deal of engineering skill, allowed the construction of buildings such as the Pantheon, (100-125), and the Coliseum.(72-80).

The Romans also used concrete for aqueducts, bridges and domes..

The Pantheon in Rome, built in 120 AD, is still the largest reinforced concrete dome in the world. With no metal skeleton, it fails current health and safety legislation.

Although the Romans used plenty of concrete, after the fall of the Empire the technology fell out of practical human knowledge for over 700 years.

Concrete was little used until 1752 when John Smeaton, an English engineer, rediscovered how to make waterproof cement and used it as mortar for a stone lighthouse at Eddystone, England.

By 1900 concrete had taken the place of a great deal of masonry and wood.


Just over 5 million barrels of concrete were required to build the Hoover Dam on the border of Arizona and Nevada. Even though it was built between 1931 and 1936, that concrete is not expected to completely set till at least 2035.

On February 15, 2014, 21,200 cubic yards, or 82 million pounds, of concrete was poured at the site of the Wilshire Grand Center, a 1,100 ft skyscraper under construction in the Financial District of Downtown Los Angeles. This broke a prior record of 21,000 cubic yards of concrete poured in one continuous pour. set during the construction of the Las Vegas hotel, The Venetian in 1999.

Computer rendering of the Wilshire Grand Center.Wikipedia Commons

The world record for the fastest time to break 16 concrete blocks on the body is 6.33 seconds, achieved by Ali Bah├žetepe from Turkey at the University in Mentese on March 18, 2015.


China consumed 6.6 gigatons of concrete between 2011 and 2013, That’s more than the US used in the entire 20th century.

The weight of the world’s tallest building, Dubai’s Burj Khalifa, is 440,000 tons. It is the equivalent to about 100,000 elephants.

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

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