A concrete cold joint forms when a pour delay lets one lift set before the next is placed, so the two never bond. It is a placement and timing issue, not a plywood defect. Here are the real causes, the time limit, how it differs from a planned construction joint, and how to. Cold joints can really weaken concrete structures, so it's important to spot and stop them from happening. This. This is known as a concrete cold joint. How do we fix these unwanted concrete pathologies, then? There. A concrete cold joint is where fresh concrete meets already hardened concrete after a delay.