REPAIR AND REHABILITATION OF BRIDGE COMPONENTS CONTAINING EPOXY-COATED REINFORCEMENT

The primary goal of this effort was to address the anticipated need for premature repair and rehabilitation of concrete bridge elements containing epoxy-coated rebar (ECR). Laboratory, test yard, and field studies were conducted to evaluate and validate applicable strategies. The performance of each strategy was judged by the level of corrosion protection afforded in and outside the repair area. Based on the results of this effort, credible information available in literature, and the collective experience of the research team, a decision matrix was developed. The decision matrix matches appropriate repair and rehabilitation strategies to the damage mode, present condition, environmental exposure, and future propensity of corrosion. The evaluation of strategies was subdivided into two categories, one applicable to the mitigation of corrosion in cracks and the other to delaminations and spalls. Several possible combinations of an epoxy injection material and two corrosion inhibitors were evaluated for corrosion mitigation in both corrosion and non-corrosion induced cracks. Injection of cracks was accomplished using bisphenol A and polyamine curing agent. Of the two surface applied (migrating) corrosion inhibitors used, one contained water based amine and an oxygenated hydrocarbon and the other contained calcium nitrite as the active agent. None of the repair strategies evaluated in this category exhibited any ability to provide protection against corrosion in the two spheres of interest, i.e., directly at the crack and the area adjacent to the cracks. Various combinations of three patch materials [pre-bagged portland cement concrete (PCC), pre-bagged polymer modified silica fume concrete, and Class III PCC], three rebar coatings (epoxy coating, water based epoxy resin/portland cement coating, and water based alkaline coating with corrosion inhibitor), and four corrosion inhibitors (water based amine and an oxygenated hydrocarbon migrating corrosion inhibitor, water based amine and an oxygenated hydrocarbon admixture, calcium nitrite admixture, and a multi-component corrosion inhibitor and concrete densifier admixture) were used in the evaluation of repair strategies applicable to delaminations and spalls. No benefit was discernable from the use of admixed and migrating corrosion inhibitors in repair areas and/or areas adjacent to the repair. The best response from a corrosion protection standpoint was demonstrated by a high resistance, low permeability silica fume modified patch material and an epoxy rebar coating compatible with ECR in the repair area. The water based alkaline coating with corrosion inhibitor showed promise in providing protection in the repair area. Impressed current cathodic protection applied to slabs for over 7.2 years successfully mitigated corrosion. The control slabs continued to corrode and experience corrosion induced damage, whereas, the cathodically protected ones did not suffer corrosion induced damage. Also, the current densities used to protect black reinforcing steel were found to be adequate to protect ECR.