Fracture prevention and repair via FRP-to-concrete joint using externally-bonded reinforcement on grooves (EBROG) technique

For the fracture prevention and structural integrity of concrete structures, extensive studies have been conducted to better understand the behavior of fiber-reinforced polymer (FRP)-concrete bond through the externally-bonded reinforcement (EBR) and the near-surface mounted (NSM) methods, and several relationships have been presented to evaluate the bond strength, effective bond length and the bond stress-slip relationship. To address the problem of premature debonding of the sheet from the concrete surface, the externally-bonded reinforcement on grooves (EBROG) was presented, which has shown the ability to eliminate the debonding in some studies. In this study, considering the two approaches of maximum load and debonding load and by conducting single-lap shear tests, the effectiveness of the EBROG method compared to the EBR method and the effect of changes in the dimensions of the groove on the FRP-concrete bond strength were investigated. To attach the FRP sheet to the concrete via the EBROG method, a single longitudinal groove with different cross-sectional dimensions (widths of 2.5, 5, 10, and 15 mm and depths of 2.5, 5, 7.5, 10, and 15 mm) was executed on the concrete surface under the center line of the sheet. The results indicated the superiority of the EBROG technique over the EBR method by 14.7-73.5% increase in the bond maximum load and 12.5-53.7% increase in the debonding load. Also, among the different grooves, the groove 10×5 mm (width×depth) was considered as the optimum groove by providing the highest maximum load and debonding load.