Post tensioning is a technique for reinforcing concrete. Post-tensioning is a form of prestressing. That means the steel is stressed (pulled or tensioned) before the concrete has to support the service loads. Most precast, prestressed concrete is actually pre-tensioned-the steel is pulled before the concrete is poured. Post-tensioned concrete means that the concrete is poured and then the tension is applied-but it is still stressed before the loads are applied so it is still prestressed. The advantages of post-tensioning are:

It reduces or eliminates shrinkage cracking-therefore no joints, or fewer joints, are needed
Cracks that do form are held tightly together
It allows slabs and other structural members to be thinner
It allows us to build slabs on expansive or soft soils
It lets us design longer spans in elevated members, like floors or beams

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