What does pre-stressed concrete mean?

Prestressed concrete is a form of concrete used in construction which is "pre-stressed" by being placed under compression prior to supporting any loads beyond its own dead weight.

Pre-stressed reinforced concrete structure(tipically its a beam or a slab). Its a type of reinforced concrete elements that contain pre-stressed steel reinforcement  at  designed places of structural elements. This technics engineers tipically use when it is required to reduce deflection of  beams,slabs or lintels. This type of  structural elements can be produced at concrete structures factories where they have all equipment in order to pre-strain reinforcement(steel bars) before concrete placement.

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Prestressed concrete is a method for overcomingconcrete's natural weakness in tension. It can be used to produce beams, floors or bridges with a longer span than is practical with ordinary reinforcedconcrete.