Isolation joint
A full-depth separation that keeps a slab from bonding to walls, columns, footings, or other slabs, so each can move independently without cracking the other.
What does isolation joint mean?
Restraint is a leading cause of cracking, and anything a slab is attached to will restrain its shrinkage. Isolation joints are placed at the perimeter, around columns and pipe penetrations, and wherever a slab meets a different structural element. They must be full depth to work; a partial separation still transmits restraint.
In practice
The compressible strip around a basement column and along the foundation wall is doing more crack prevention than the mesh in the slab.