What does proper preparation of the surface before resuming a concrete pour help avoid?

Proper surface preparation before resuming a concrete pour plays a crucial role in ensuring that the new concrete bonds effectively with the existing layer. One of the main concerns is the formation of cold joints, which occur when fresh concrete is poured onto older concrete that has begun to set. If the surface is not properly prepared, this transition can create a weak point in the structure where the two layers do not adhere well, resulting in a cold joint.

When the surface is adequately prepared—by cleaning, removing any debris, and sometimes wetting the old surface or applying a bonding agent—it promotes a strong bond between the layers. This preparation helps to ensure continuity in the concrete structure, maintaining strength and integrity. Therefore, avoiding cold joints is fundamentally tied to the proper surface preparation prior to continuing with a concrete pour.