How-To: cut a channel in concrete?
High carbon steel cables, coated with grease and a plastic sleeve are laid throughout the slab (although a whole lot less than normal rebar), with one end terminating into an anchor, and the other end left loose outside the slab.
After the slab is placed and cured, a machine is attached to the loose end of the cable that pulls it to a certain amount of tension. That end is then restrained, the excess cable is cut off and the hole patched. This puts the entire slab under compression, which is a very good way to prevent slab failure.
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