Concrete

**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. Types of Concrete's Construction **__Reinforced Concrete Construction__ ** Was developed to add the tensile strength of steel to the compressive strength of mass concrete. The metal is embedded by being set as a mesh into forms before pouring, and in the hardened material the two act uniformly. The combination is much more versatile than either product; it serves not only for constructing rigid frames but also for foundations, columns, walls, floors, and a limitless variety of coverings, and it does not require the addition of other structural materials. Although the making of forms is a slow and costly process, the technique competes economically with steel frame construction because the mesh, composed of thin, bendable metal rods or metal fabric, employs far less steel, and is itself inexpensive . **__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.

**__Prestressed concrete construction__**

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.