Concrete
Cold Joint
A plane of weakness in concrete that forms when fresh concrete is placed against concrete that has already set, preventing full bonding between the layers.
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In the Field
Cold joints happen when pours are delayed too long or when sections are poured on different days without proper preparation. They are a defect — not an intentional construction joint. Prevent them by planning continuous pours and maintaining a live working face.
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Rule of Thumb
If concrete has been sitting more than 90 minutes in normal temperatures, treat the surface as a cold joint: clean it, apply bonding agent, and get engineer approval before continuing.