The search for economical foundations for residential and light commercial construction following World War II led to the use of ground supported reinforced concrete slabs called floating slabs. In the 1960s, post-tensioning was adapted to the construction of these light-duty slabs on grade in an effort to improve crack control and reduce cost and slab deflection. Since then, the use of post-tensioning in slab-on-grade construction has also grown to include industrial floors.
The design for a post-tensioned slab on grade is simpler than that of a conventional slab. Instead of welded wire fabric or conventional rebar, a grid of high-strength post-tensioning tendons is set in the middle of the slab. The prestressing force is transferred from the tendons to the concrete through anchorage devices at the ends of the tendon and through two wedges inside the anchorage devices. The result is an internal compressive force in the concrete that enhances its resistance to cracking under load or cracking due to concrete shrinkage or temperature variations.