Concrete

==== Concrete is a mixture of cement and water and other elements such as sand and stones. While it is in its liquid state, it can be molded in a variety of forms, that’s why it is often used in construction, it is cheap in contrast with other materials in construction and it also has a very important advantage compared to them, its absence of join- points. ====

==== This material has been used since the Egyptian times; also we can find it in Greek and Roman constructions (the ancient temples). ====

==== The reinforced- concrete is nothing but the development of the tensile strength of steel mixed with the compression of concrete. The way it is used is embedding the steel first and then pouring the concrete in its liquid state, thus this make it a very useful way to build any form you can imagine, from rectangular shapes to domes to sharper planes. The steel reinforcement is employed to take full advantage of the plastic, or sculptural, character of concrete. It can be joined or bent to unify supporting members with the floors and the coverings they carry. ====

==== An important discovering from the 20th century was the concrete- shell constructions, were the quantity of steel is reduced to its minimum expression and the pouring of concrete does all the structural work. Also the pre- cast concrete was another super important development, which employs bricks, slabs, and supports made under optimal factory conditions to increase waterproofing and solidity, to decrease time and cost in erection, and to reduce expansion and contractions. And finally, pre- stressed concrete provides bearing members into which reinforcement is set under tension to produce a live force to resist a particular load. Since the member acts like a spring, it can carry a greater load than an unstressed member of the same size. ====

====.- Concrete is a manufactured mixture of cement and water, with aggregates of sand and stones, which hardens rapidly by chemical combination to a stonelike, water-and-fire-resisting solid of great compressive but low tensile strength. ====

.- Pozzolana: Volcanic- ash cement.
====.- Concrete-shell construction permits the erection of vast vaults and domes with a concrete and steel content so reduced that the thickness is comparatively less than that of an eggshell. ==== ====.- Precast-concrete construction, employs bricks, slabs, and supports made under optimal factory conditions to increase waterproofing and solidity, to decrease time and cost in erection, and to reduce expansion and contractions. ==== ====.- Pre- stressed concrete provides bearing members into which reinforcement is set under tension to produce a live force to resist a particular load. Since the member acts like a spring, it can carry a greater load than an unstressed member of the same size. ====