Concrete

Concrete is a construction material made with cement, water, aggregates like stones, sand limestone and others, and chemicals (used to change its properties according to the structure). It was already known and used in Egypt and ancient Rome. Romans used concrete to build bridges, sewerage systems and temples such as the Pantheon in Rome. And, even when all this knowledge was lost during the Dark Ages, it was regained in the 18th century, and today is one of the most widely used materials in the world. It`s been used to build bridges, columns, arches and vaults, load-bearing walls, and so on. But this material, believe it or not, presents some disadvantages (the material is weak in tension, for example). Because of this, several solutions have been found. In 1867, Joseph Monier earned his patent for **reinforced concrete** (original concrete with metal elements placed as a mesh before the material is poured). And in the 20th century, the production reached a whole new level with three more developments.




 * Concrete-shell constructions ** don’t have support structures such as columns or load-bearing walls, because of their natural strength. The most common shapes are flat plates or domes, but they also can be built using ellipsoids or cylindrical shapes (as the one in the picture).
 * Precast concrete ** is used when there is no obligation of pour the concrete in site. Instead, it can be transported directly from the plant (landscaping structures, security walls, beams ). Or also, when the structure is made of a standard shape that can be replicated over and over again ( water and sewage pipes, tunnels, even houses).




 * Pre-stresse **** d concrete ** is used when there`s the need of overcome the natural weakness of concrete: tension. It is used to build bridges, floors, beams and other elements with a longer span than reinforced concrete.