The precast prestressed concrete units are erected first and can be used to support the formwork needed for the cast in situ slabs without additional scaffolding (or shoring). In addition to its contribution to the strength and stiffness of the composite member, the cast in situ slabs provides an effective means to distribute loads in the lateral direction. The cast in situ slabs can be poured continuously over the supports of precast units placed in series, thus providing continuity to a simple span system.
Pre-tensioning in the plant is more cost-effective than post-tensioning on site. Because the precast 4 prestressed concrete element is factory-produced and contains the bulk of reinforcement, rigorous quality control and higher mechanical properties can be achieved at relatively low cost. The cast in situ concrete slab does not need to have high mechanical properties and thus is suitable for field conditions.
