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The Romans used concrete extensively from 300 BC to 476 AD. Concrete was used for construction in many ancient structures. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete. Lime mortars were used in Greece, Crete, and Cyprus in 800 BC. In the Ancient Egyptian and later Roman eras, builders discovered that adding volcanic ash to the mix allowed it to set underwater.Ĭoncrete floors were found in the royal palace of Tiryns, Greece, which dates roughly to 1400-1200 BC. In contrast to modern concrete structures, the concrete used in Roman buildings was usually covered with brick or stone. Opus caementicium exposed in a characteristic Roman arch. Some of these structures survive to this day. They kept the cisterns secret as these enabled the Nabataeans to thrive in the desert. They built kilns to supply mortar for the construction of rubble masonry houses, concrete floors, and underground waterproof cisterns. They discovered the advantages of hydraulic lime, with some self-cementing properties, by 700 BC.

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Small-scale production of concrete-like materials was pioneered by the Nabatean traders who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan from the 4th century BC. 'The floors were cement, in some places hard, but, by long exposure, broken, and now crumbling under the feet.' 'But throughout the wall was solid, and consisting of large stones imbedded in mortar, almost as hard as rock.' 'The roof is flat and had been covered with cement'. Mayan concrete at the ruins of Uxmal (850-925 A.D.) is referenced in Incidents of Travel in the Yucatán by John L. The word concrete comes from the Latin word ' concretus' (meaning compact or condensed), the perfect passive participle of ' concrescere', from ' con-' (together) and ' crescere' (to grow). Some methods of concrete manufacture and repair involve pumping grout into the gaps to make up a solid mass in situ. It does not contain coarse aggregates and is usually either pourable or thixotropic, and is used to fill gaps between masonry components or coarse aggregate which has already been put in place. Grout is another material associated with concrete and cement. Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks, tiles and other masonry units together. Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder. In the past, lime based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements, (water resistant) such as a calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone). Most concrete is poured with reinforcing materials (such as steel rebar) embedded to provide tensile strength, yielding reinforced concrete.

Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. The hydration process is exothermic, which means ambient temperature plays a significant role in how long it takes concrete to set. This time allows concrete to not only be cast in forms, but also to have a variety of tooled processes preformed. The cement reacts with the water through a process called concrete hydration that hardens it over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Concrete is a composite material composed of aggregate bonded together with a fluid cement that cures over time.

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