Cold Joint

A cold joint is a discontinuity that forms within a concrete element when a batch is placed against concrete that has already begun to set, rather than while it is still plastic. The result is a visible line and, more importantly, a plane that is weaker than the surrounding monolithic concrete.

Cold joints are typically avoided by planning pour sequencing and truck timing so that each load arrives before the previous one sets — the same scheduling discipline that determines how often a washout pan needs to be swapped.