Isolation and expansion joints accommodate anticipated differential horizontal and vertical movements that occur between a pavement and a structure. Their purpose is to allow movement without damaging adjacent structures. Contraction or control joints also absorb some movement; however their main function is to control the location and geometry of the natural cracking pattern in a concrete slab.

 

Because pavement performance can be significantly affected by the planned use and location of isolation and expansion joints, care should be taken in their design. Though the terms are sometimes used interchangeably, isolation joints are not expansion joints.