An rubber expansion joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials, to absorb vibration, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of sidewalks, bridges, railway tracks, piping systems, and other structures.Throughout the year, building faces, concrete slabs, and pipelines will expand and contract due to the warming and cooling through seasonal variation, or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under the stress induced.