Concrete is strong in compression but relatively weak in tension.  Post-Tensioning precompresses the concrete with a force that has to be overcome prior to relying on its own flexural strength and therefore optimizes the use of steel.  This helps to control shrinkage cracks in the early stages of the life of the slab and allows you to use less concrete.

• Controls and potentially eliminates cracks
• Requires less concrete in slabs
• P.T.  slabs are much stronger than most rebar slabs.  A rebar slab equivalent in strength would be more costly
• Speed and ease of installation.  PT goes in faster than conventional steel and can be a big advantage with inclement weather and gives you greater flexibility over project scheduling
• Fewer joints in slabs
• Deflection control
• Engineered slab

1967 test slab with 15 1/2' undercut; 4 ' slab with thickened edge.  Total weight of 110,000 lbs.  from lead weights and bulldozer illustrates the ability of post-tensioned concrete to cantilever and span sub-base soft spots.