The Assyrians and Babylonians used clay as the mortar, whilst the Egyptians used a mortar that contained gypsum for pyramid building. The Greeks and Romans used slaked lime as a mortar in many of their buildings. Slaked lime is made by heating limestone to form lime , which is then 'slaked', that is reacted with water

Unfortunately, mortars made with slaked lime tended to crack and crumble when exposed to weather, so both the Greeks and the Romans found a much more satisfactory cement called 'pozzolana'. This was made from finely ground lime, sand and a volcanic material that was found in particular near the Italian town of Pozzuoli. Pozzolana cement set hard when water was added to it. This type of cement was used in building both the Pantheon and the Colosseum and remained in use until the late 18th century, although the quality deteriorated in the period after the Romans

John Smeaton , who was commissioned to rebuild the Eddystone lighthouse off the coast of Cornwall, experimented with hydraulic cements made by heating limestone and clay to eliminate water and carbon dioxide , and found a product that was superior to pozzolana cement for underwater use

Note: Smeaton's tower, completed in 1759, was made of one thousand tons of granite and Portland stone. It stood 72 feet (22m) tall on one of the most notorious reefs in the English Channel, 14 miles (22.5km) off the coast of Plymouth. It was moved, stone by stone, to Plymouth Hoe when the present lighthouse, Douglass's tower, was built in 1882

In 1824, Joseph Aspdin , a British bricklayer, heated a mixture of finely ground limestone and clay in his kitchen stove and ground the mixture into a powder to produce a hydraulic cement. He patented the process in England and called it Portland cement . The name, which is not a brand name, was used because of a slight similarity between the set cement and Portland stone. This process used a higher temperature than had been used before and produced a much-improved strength. Modern cement manufacturing is based upon John Aspdin's process

Cement is the essential ingredient in concrete and has become the second most consumed substance in the world after water. Every house, road, bridge, hospital, school, airport runway, office block, factory, etc. relies upon concrete for its construction. The cement industry contributes £775 million annually to the UK economy. It operates 14 plants and produces around 12 million tonnes of Portland cement a year, which represents about 90 % of the cement sold in the UK. It is difficult to imagine a modern world without cement.

However, cement is one of the most environmentally hazardous materials in the world, adding more carbon dioxide to the atmosphere than the entire global airline industry. A report by the Sustainable Development Commission shows that 4% of carbon dioxide pollution is caused by the aviation industry, whilst between 5% and 10% is caused by the manufacture of cement based building materials, including the production of concrete and asphalt