Concrete is one of mankind’s oldest technological innovations. The Romans were the first to take advantage of the inherent strengths of concrete. Roman pozzolan concrete structures as the Coliseum, the Pantheon, the Baths of Caracalla, and the aqueduct called the Pont du Gard, are just a few of the many famous Roman buildings still standing. The domed Pantheon, built over 7 yrs circa a.d. 180, is still being used.
King Herod built Caesarea Maritima around 2000 years ago on the coast of present-day Israel. In order to create a harbor, barges were filled with a hydraulic concrete and then sunk in a checkerboard pattern to provide the framework for harbor sea walls. The sea would then deposit silt in the voids that were then capped with gravel and concrete to complete the structure.
Although not the first documented use of hydraulic concrete (the first documented use was in the construction of the Coca, Italy harbor in the 1st half of the 2nd century BC), Caesarea with its 100 acre enclosed harbor was certainly one of the grandest harbor projects undertaken until modern times. If not for a change in sea level, it might still be in use today
With the decline of the Roman Empire and onset of a Dark Age over Europe, the use of concrete almost disappeared. It was not until the late 18th century that patent Roman cements began to be used with some success. In 1824 Joseph Asp din burned finely divided clay with finely divided chalk in a lime kiln until the carbon was burned off to produce what was termed Portland Cement, a direct ancestor of the Portland cement used today. In 1828 Portland based concrete proved its usefulness when it was used to plug a breach in the Thames tunnel.
As the 19th century continued, the pace of concrete development quickened. Reinforced concrete first appeared in 1867 within flowerpots. By 1889 with the development of high temperature rotary kilns, the first steel reinforced bridge was built.
The improvements continued in the 20th century. The use of rotary kilns was standardized with the patent issued to Thomas Edison. Edison built low-income housing in 1908 to prove the efficacy of reinforced concrete as an economical building material. These homes are still in use.
In the late 20’s Linus Pauling developed principles to help understand the structure of complex silicates. 1930 brought about the development of air-entraining agents that allow a greater freeze-thaw range for concrete. This in turn allowed the use of concrete to build the Hoover Dam (1936) and other major public works structures. During the 1970’s fiber additives were first used to increase tensile strengths in concrete. In the 1980s the first use of superplasticisers was recorded. Superplasticisers reduce the amount of water required to activate cement by making water wetter; less water makes stronger concrete.
Concrete continues its development today. In Roman times concrete was considered an ideal building material, but was not considered sightly. The Romans took great pains to cover their concrete structures with stone facades. Thanks to over 2 millennia of developments, Stone Soup is helping to move concrete forward. Not only is our concrete hard and impermeable, with great tensile strength, but it is also beautiful. We are proud to be part of the development of a substance that has played such an important witness to history.