Reinforced concrete members must carry their own weight as well as any applied loads. This means that conventional reinforced concrete planks must have short spans and thick section depths. Pre-stressing of precast concrete planks overcomes this limitation. In pre-stressing, high-tensile steel strands are stretched between abutments at each end of casting beds. Concrete is then placed to encase the strands. As the concrete cures, it bonds to the tensioned steel. When the concrete has reached a specified strength, the tensioned strands are released from the abutments. This exerts pressure upon the lower portion of the member, which stresses the concrete, and in effect relieves the precast plank from the need to support or carry its own weight. This pre-stress force gives Spancrete Hollowcore plank its slight upward arch or camber.

Span Notes (stored as PDFs):

Advantages of prestressed concrete