Integrity of CFRP-Concrete Interface in Sulfuric Acid

This paper presents the interfacial behavior and deterioration mechanisms of carbon fiber-reinforced polymer (CFRP) sheets bonded to a concrete substrate subjected to sulfuric acid based on a test protocol suggested by published guidelines. To represent possible scenarios on-site, two groups were tested: Category 1 is for CFRP-strengthened concrete members experiencing acid exposure owing to a functional change, and Category 2 is concerned with acid-damaged concrete that requires CFRP strengthening. All specimens were conditioned in a 5%-concentration sulfuric acid solution for up to 9 weeks at a typical interval of 3 weeks. Chemical interactions between the test specimens and sulfuric acid are affected by the presence of CFRP bonding, thereby lowering the dissolution of the cement paste. The capacity of the interface decreases due to the acidic environment, which is rapid at an early exposure period between 0 and 3 weeks. CFRP debonding in conjunction with notch-induced concrete cracking is responsible for the specimens' failure, regardless of exposure period. The specimens in Category 1 reveal an apparent transition from full bond to debonding when failure is imminent, which is different from those in Category 2 accompanied by gradual interface degradation. The extent of composite action between the CFRP and concrete is a function of exposure period and load level. An analytical model is developed to propose performance-based design recommendations that are dependent upon variable safety indices and interfacial deterioration levels. (C) 2018 American Society of Civil Engineers.