The History of Concrete
Concrete is a construction material composed of cement (commonly portland cement) as well as other cementitious materials such as fly ash and slag cement, aggregate (generally a course aggregate such as gravel, limestone or granite, plus a fine aggregate such as sand), water, and chemical admixtures. The word concrete comes from the latin word “concretus”, meaning compact or condensed.
The Assyrians and Babylonians used clay as their bonding substance or cement. The Egyptians used lime and gypsum cement. The widespread use of concrete in many Roman structures has ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges have masonry cladding on a concrete core, as does the dome of the Pantheon.
Some have stated that the secret of concrete was lost for 13 centuries until 1756 when British engineer John Smeaton made the first modern concrete (hydraulic cement) by adding pebbles as a course aggregate and mixing powdered brick into the cement. In 1824, English inventor Joseph Aspdin invented Portland Cement, which has remained as the dominant cement used in concrete production. He created the first true artificial cement by burning ground limestone and clay together. The burning process changed the chemical properties of the materials and created a stronger bond than what using plain crushed limestone would produce.
The other major ingredient of concrete besides cement is the aggregate. Aggregate can be sand, crushed stone, gravel, lsag, ashes, buned shale and burned clay, and even crushed glass or nails for more creative surfaces when the concrete is polished.
Concrete that includes embedded material (usually steel) is called reinforced concrete. Reinforced concrete was invented by Joseph Monier in 1849 and who received a patent in 1867. Joseph Monier was a Parisian gardener who made garden pots and tubs of concrete reinforced with an iron mesh. Reinforced concrete combines the tensil strength of metal and the compressional strength of concrete to withstand heavy loads. Joseph Monier exhibited his invention at the Paris Exposition in 1867. Besides his pots and tubs, he promoted reinforced concrete for use in railway ties, pipes, floors, arches and bridges.
Concrete is used more that any other man made material in the world. As of 2006, about 7.5 billion cubic meters of concrete are made each year—more than one cubic meter for every person on Earth. Concrete powers a US$35 billion industry, employing more than two million workers in the United States alone. More than 55,000 miles (89,000 km) of highways in the United States are paved with this material.
The world record for the largest concrete pour in a single project is the Three Gorges Dam in Hubei Province, China by the Three Gorges Corporation. The amount of concrete used in the construction of the dam is estimated at 16 million cubic meters over 17 years.