Spalling is a condition wherein your concrete develops a series of scales or large concrete chips. The spalled surface appears to crumble away from the surrounding concrete. Spalling is generally caused by carbonation of the concrete where carbon dioxide reacts to chemicals within the concrete. The steel reinforcing bars within the concrete begin to corrode and expand, causing the breakage on the surface concrete. If caught early, spalling can be repaired, removing the need for complete concrete replacement.