We're repairing a dam face that has suffered freeze-thaw deterioration to depths ranging from six inches to 2 1/2 feet. The deteriorated concrete was removed by hydrodemolition. We're installing the formwork now and will begin pouring the repair concrete soon. The specifications require placing a polyvinyl acetate bonding agent onto the existing concrete before placing the repair concrete. Is this the right bonding agent to use? Is a bonding agent even required for this application?
This is not a good application for a polyvinyl acetate bonding agent. According to ACI 546R- 96, Concrete Repair Guide, polyvinyl acetate should not be used in applications that may be exposed to moisture. The Bureau of Reclamation's Guide to Concrete Repair recommends using an epoxy bonding agent for repairs that are less than six inches thick. According to the guide, thin repairs are subject to poor curing conditions caused by moisture evaporation and capillary absorption by the base concrete and, therefore, rarely develop acceptable bond strengths. Thicker repairs, however, do not require a bonding agent.