Effect of Concrete Substrate Repair Methods for Beams Aged by Accelerated Corrosion and Strengthened with CFRP

Abstract

The deterioration of concrete structures, particularly highway bridges, has motivated the use of fiber-reinforced polymer (FRP) composites for retrofitting damaged components, typically using externally bonded carbon fabrics or laminates (CFRP). The application of this technology in practice has been highly successful, but there are concerns about its long-term performance and durability. Numerous studies have been devoted to the durability of concrete-FRP interface regarding bond evaluation and potential for delamination, but not much information is available on the effects of concrete substrate repair for deteriorated components, which is a necessary step before application of FRP reinforcement. This paper is part of a comprehensive rehabilitation program with CFRP of nearly 1,000 concrete T-beam bridges for the Pennsylvania Department of Transportation. The focus of this paper is on an exploratory study to evaluate the most effective concrete substrate repair method for damaged concrete beams by accelerated corrosion, subsequently reinforced for flexure with CFRP fabric and tested to failure. The contributions of this paper are, however, much broader, and provide valuable guidelines to design a comprehensive research program on this topic as well as sufficient practical recommendations for applications in practice, including (1) an in-depth literature review with a useful summary reference table; (2) a prescription for producing porous, chloride-contaminated, and low-strength concrete, to simulate field conditions on the basis of microstructure evaluations of collected samples; (3) advice on proper implementation of accelerated corrosion to achieve consistency of results and, more importantly, to achieve damage characteristics resembling closely observed field conditions; and (4) evaluation of two widely used substrate repair methods: (a) polymer crack-injection and (b) replacement of concrete cover with polymer-modified concrete (PMC) containing corrosion inhibitor. The experimental program consisted of testing large-scale beams [