Cold joints are formed primarily between two batches of concrete where the delivery and placement of the second batch has been delayed and the initial placed and compacted concrete has started to set. The full knitting together of the two batches of concrete under vibration to form a homogeneous. A cold joint in concrete is an area or surface with a structural discontinuity caused by the delayed concrete pouring between two layers of concrete. This discontinuity occurs because the older material has passed its initial setting time, preventing a true chemical bond with the fresh mix.