A cold joint in concrete construction is a plane of weakness that forms when new, wet concrete is poured against concrete that has already begun to harden. This discontinuity occurs because the older material has passed its initial setting time, preventing a true chemical bond with the fresh mix. What is a Cold Joint in Concrete? Why does a Concrete cold. POST a QUESTION or COMMENT about concrete cold pour joints, definition, identification, causes, troubleshooting, repair. Concrete foundation cold pour joints: This article describes the appearance, cause, & problems that may occur at cold pour joints in concrete foundation walls and occasionally. These sneaky little rascals can turn your sturdy foundation into a wobbly mess faster than you can say “oops. Spoiler alert: it's not the kind of party you want.