Prestressed Concrete is an architectural and structural material possessing great strength. The unique characteristics of prestressed concrete allow predetermined, engineering stresses to be placed in members to counteract stresses that occur when the unit is subjected to service loads. This is accomplished by combining the the best properties of two quality materials: high strength concrete for compression and high tensile strength steel strands for tension.
Actually, prestressing is quite simple. High tensile strands are stretched between abutments at each end of long casting beds. Concrete is then poured into the forms encasing the strands. As the concrete sets, it bonds to the tensioned steel. When the concrete reaches a specific strength, the strands are released from the abutments. This compresses the concrete, arches the member, and creates a built in resistance to service loads.