As a rule of thumb, we recommend that the time gap between the two batches does not exceed 30 minutes. Technically speaking, other factors can influence this time horizon, such as local temperature, type of cement used, concrete mix, etc. Learn how to prep and bond a next-day concrete pour to repair a cold joint. Identify cold. Properly executed, cold jointing ensures structural integrity and minimizes the risk of cracks or weaknesses at the joint. If the concrete is placed before it becomes stiff or hard to remold or does not rise with extensive vibration, the joint should be left for 12 to 24 hours to harden.