Expansion joint

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An expansion joint is an assembly designed to safely absorb the heat-induced expansion and contraction of various construction materials. They are commonly found between sections of sidewalks, bridges, railway tracks, piping systems, and other structures.

The "assembly" can be as simple as a caulked separation between two sections of the same materials. More recently, expansion joints have been included in the design of, or added to existing, brick exterior veneer walls for similar purposes. In concrete and concrete block ("CMU") construction, the term applied is "control joint", but serves similar purposes.

Pipe expansion joints are necessary in systems that convey high temperature commodities such as steam or compressed air. One type of expansion joints for pipe systems is a bellows which can be manufactured from metal or an elastomer such as rubber. The bellows are designed to withstand the internal pressures of the pipe but are flexible enough to accept axial, lateral, and angular deflections.

Throughout the year, building faces and concrete slabs will expand and contract due to the warming and cooling of our planet through the seasons. Before expansion joint gaps were built into the structures we see today, the structures would crack under this stress (thermal expansion and contraction). Expansion joints are often neglected during the design process,^{[citation needed]} and simple caulking is used to fill these gaps to complete a project. This simple caulking cannot handle the thermal expansion due to the changing seasons, ultimately leaving a leak point in the structure.^{[citation needed]} Stuffing material placed in these gaps helps to keep the building from cracking and leaking heat or cool air.

[edit] Roadway expansion joints

Expansion joints are cut into the concrete or asphalt to help with expansion and contraction of the material through the change in temperature. The joints are cut at regular intervals to prevent random cracking of the roadway. The first cut is done with a saw using a green saw blade which is usually 1/4 inch thick. After the concrete has completely cured the joint is then widened to a thickness of 3/4 inch. Roadway expansion joints can be sealed with hot pour (tar), cold sealant (silicone), or compression sealant (rubber).

[edit] See also

• Slip joint

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