Q.: What causes spalling in concrete parking lots?

A.: Spalling at joints can occur after stones, dirt and debris get into the joints when they are open. When the joints attempt to close in hot weather a large localized resistance causes breakage. Repeated action may make spalling at joints extensive. Deterioration caused by repeated exposure of non-air-entrained concrete to freezing and thawing in the saturated condition or to the action of deicer salts can also cause spalling. The remedies are to provide joints of proper design and spacing, sealing joints properly with good materials, using air-entrained concrete, curing properly, and not applying deicers during the first winter.