ACI PRC-364.7-21

What is concrete bruising, how is it evaluated, and how can it be minimized? Bruising refers to damage in a surface layer of remaining substrate concrete that is weakened by fine interconnected cracks caused by the use of high-impact, mechanical methods for concrete removal and surface preparation. The bruised (or fractured) layer left by such surface preparation methods typically extends to a depth of 1/8 to 3/8 in. (3 to 10 mm) or more below the remaining substrate surface and, if not removed, generally results in lower repair bond strengths. Bruising, which can be detected through pulloff testing and petrographic examination, can be effectively minimized by selecting the most appropriate method and equipment for the given application.