Reinforced concrete. A short history

The oldest known form of concrete (hard chemically inert particulate substance that is bonded together by cement and water; aggregates include sand, crushed stone, gravel, slag, ashes, burned shale, and burned clay) is to be found in the Middle East and it dates back to 5600 B.C. In Serbia, remains of a hut dating from 5600 BC with a floor made of red lime, sand, and gravel. The pyramids of Shaanxi in China (about 4000 B.C.) contain a mixture of lime and volcanic clay). The Egyptians (XXVI century B.C.) used mixed with straw to bind dried bricks, gypsum and lime mortars in stone masonry (in particular for the construction of pyramids); the Assyrians and Babylonians used clay as the bonding substance instead. The Greeks inhabitants in Crete and Cyprus used lime mortars as well (Eight century B.C.), whereas Babylonians and Syrians used bitumen to construct stone and brick masonries. Ancient Greeks, similarly, used claimed limestone, while Romans made the first concrete (opus caementicium): mixed lime putty with brick dust or volcanic ash; Romans used with stone to construct roadways, buildings and aqueducts and walls around a fourth-century B.C. and "by the second century B.C. the new material began to be used for buildings in Rome" (Elliot C. D.,1992, p. 167). B. Herring and S. Miller wrote (Miller S., 2002, p.16): Lime-coated mud walls were constructed in central India as early as 2,500 B.C., and many early civilizations, including that of the Romans, used it as a sort of stucco covering for mud walls and other crude structures. When it comes to actual concrete, the Greeks used a highly durable mix as early 1,700 B.C., as revealed by Italian archaeological digs. "We removed this very hard concrete, a process which caused the breaking of hundreds of our picks," notes author D. Livi in The Italian Excavations in Crete and the Earliest European Civilization. It is not known exactly when the Romans first began mixing lime with other substances to form concrete, but "archaeological studies have noted that a wall of rubble in Pompeii was held together with a firm black pozzolan and lime mortar dating to the late third century before Christ," notes Moore, citing archaeologist M. E. Blake. It is also known from ancient writings that by 199 B.C. the Romans were already using hydraulic concrete to line the harbour works at Puteoli, which indicates a striking degree of sophistication