Concrete, in its earliest form, was invented around 6500 BC by the Nabataea traders in the regions of southern Syria and northern Jordan. They created concrete-like floors, housing structures, and underground waterproof cisterns using hydraulic lime, a cementing material that hardens underwater. Earlier than that, precursors to concrete appeared in various ancient civilizations. For example, around 1300 BC, Middle Eastern builders used a form of cement by coating pounded-clay structures with burned limestone, which chemically hardened. Ancient Egyptians and Romans also used variations of cementitious materials, with the Romans widely using concrete by 200 BC made from volcanic ash, lime, and seawater. The modern form of concrete, using Portland cement, was invented much later in 1824 by Joseph Aspdin in England. He created an improved cement by heating chalk and clay, which led to the mass production and widespread use of concrete similar to how it is used today. Thus, concrete has been invented and evolved multiple times in history, with its earliest use dating back about 8,500 years ago in the Middle East and its modern invention in the 19th century.
