Concrete is a stone-like man-made material composed of cement with aggregate (small pebbles) and sufficient water. When these ingredients are mixed together, they achieve a fluidity that is easily molded into shape. Concrete is normally reinforced with the use of rods (like rebar) or steel mesh before it is poured into molds. Over time, the cement hardens, binding the rest of the ingredients together into a durable stone-like material with many uses.
The history of concrete dates back to Rome 2000 years ago. Concrete was widely used in the Roman Empire. The Colosseum in Rome was built largely of concrete, and the concrete dome of the Pantheon is the world's largest unreinforced concrete dome. Concrete was essentially used in aqueducts and roadway construction in Rome.
The Romans used a primitive mix for their concrete consisting of small gravel and coarse sand mixed with hot lime, and water, and sometimes added pozzolanic ash, and even animal fat, milk, and blood. To trim down shrinkage, they are known to have used horsehair.
Early Romans built some 5,300 miles of roads using concrete.
Modern structural concrete differs from Roman concrete in two important ways:.
First, its mix consistency is fluid, 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.
The Assyrians and Babylonians used clay as the bonding substance or cement.
The Egyptians used lime and gypsum cement. Lime mortars and gypsums were also used in building the world-acclaimed pyramids.
The use of concrete became rare after the Roman Empire collapsed, until the technology was re-pioneered in the mid-18th century.
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The first modern concrete (hydraulic cement) was made by British engineer, John Smeaton In 1756, by adding pebbles as a coarse aggregate and mixing powdered brick into the cement. In 1793, he built the Eddystone Lighthouse in Cornwall, England with the use of hydraulic cement.
Portland Cement, which has remained the dominant cement used in concrete production, was invented in 1824 by English inventor Joseph Aspdin, who created the first true artificial cement by burning ground limestone and clay together in a lime kiln until the carbon dioxide evaporated, resulting in strong cement. The burning process changed the chemical properties of the materials and Joseph Aspdin created a stronger cement than using plain crushed limestone would produce.
The first test for the tensile and compressive strength of concrete was in Germany in 1836. Another main ingredient of concrete is aggregate and includes sand, crushed stone, clay, gravel, slag and shale. Concrete that uses embedded metal is called reinforced concrete or Ferroconcrete.
Joseph Monier first invented reinforced concrete in 1849. He was a gardener who made flower pots and tubs of reinforced concrete with the use of iron mesh. The reinforced concrete thus combined the tensile power of metal and the compression strength of concrete for tolerating heavy loads. He received a patent for this invention in the year 1867.
The first rotary kiln that made constant production of cement was introduced in England in 1891.
The first concrete street was made by George Bartholomew in Ohio. By 1920s, concrete found major usage in construction of roads and buildings.
The first concrete dams, the Hoover and the Grand Cooley were built in 1936.
Concrete is the most widely used man-made material today (measured by tonnage).
There has been no looking back for concrete since its modern development. Today, new technologies continue to develop. In addition to it’s well deserved standing as the most popularly used building material, with the advent of new techniques such as Concrete Polishing and Staining, the status of modern concrete has been elevated to use as a decorative element.
