Göbekli Tepe is a mysterious structure built in Turkey somewhere around 10000 BCE. It displays some of the earliest signs of concrete use, although scholars remain baffled of its purpose. The floors of the purported temple are made of a composite cement material still visible today.
By 6500 BCE we are given some of the earliest written records of concrete use. The Nabataean traders, a nomadic Bedouin tribe that travelled the Arabian Desert, created their housing structures, underground wells (cisterns) and created their floors all with concrete when they eventually settled. With local access to fine silica sand, they added this to their cement creations to waterproof it.
Ancient Egypt formed their bricks by mixing mud and straw together, while also using gypsum and lime to create mortars by 3000 BCE. The Great Pyramids at Giza were erected around then, using somewhere around 500,000 tons of mortar. Some 5,000 miles away, the Chinese were just starting to lay some of the earliest foundations for the Great Wall of China. They also used cement-like materials to hold bamboo together in their boats. Sections of the wall were held together by a paste made of sticky rice flour and slaked lime. The mortar worked so well and bound the bricks so tightly that not even now can weeds grow in some areas.
Come 600 BCE, Ancient Greeks discovered pozzolan, a type of natural siliceous material derived from volcanic ash. Pozzolan is named after where it was originally found in Pozzuoli, Italy. This, combined with heated limestone, made a mortar to use as Ancient Greeks were more than likely the first of the ancient civilizations to utilize hydraulic mortars, a mortar (usually lime) that mixed with water that hardened in both air and water.
The Romans took what both the Greeks, but also the Nabataeans knew and added their own touch. They improved upon previous cultures’ information, their version of mortar used in the creation of large-scale coastal seawalls throughout the Mediterranean.
Steel reinforcement didn’t exist during this time, and instead, they used a concrete mix packed into wooden forms. When Rome expanded out into Western Europe, and the volcanic ash became scarce, Roman builders relied upon crushed brick and tile. This is likely one of the earliest examples of manipulating the properties of cementitious materials for specific uses.
Some two-thousand years later, their magnificent buildings Pantheon and the Colosseum still stands as a testament to their ingenuity.
Following political corruption, civil wars, and outside attackers from overextended borders, the Roman Empire fell in 476 CE. With its splintering, most of the technology from this time was also lost. The overall quality of building materials of the Middle Ages deteriorated from the lost technique. It wasn’t until 1414 CE that people located manuscripts describing the pozzolan cement were found, revitalizing interest.
Technology stagnated for a few hundred years until 1793, when John Smeaton discovered a modern method for producing hydraulic lime for cement. Limestone that contained clay was fired until it became clinker (the residual stony remnants) and ground into powder. He used this material to rebuild historic Eddystone Lighthouse located in Cornwall, England.
Portland cement, one of the most commonly used around the world as a basic ingredient in mortar, stucco, concrete and non-specialty gout, was invented by Joseph Aspdin in 1824. He combined finely ground chalk and clay in a lime kiln until it burned off carbon dioxide. The ending product was ground up, then added into a cement named after the stones quarried in Portland, England.
For most of the 19th century, due to aesthetic reasons, it was socially unacceptable to use as a building material for homes. Instead most of it went into creating industrial buildings. The first widespread use of Portland cement by the general population didn’t come until 1850 to 1880 by Francois Coignant, who added steel rods to prevent the spreading of exterior walls. From then on, concrete became a staple in the construction of homes, streets, and larger structures like the Hoover Dam.
The first patent for a portable concrete mixer was applied and developed in 1916, a rudimentary machine that replaced horse-drawn mixers. It was cumbersome and slow but did the job. Technology has improved drastically since then with vehicles capable of handling thousands of pounds of wet and unset concrete. Further advancements make it possible to mix concrete right where the job is, and have become the quintessential part of a construction site.