Experimental evaluation of FRP-concrete bond using externally-bonded reinforcement on grooves (EBROG) method

Despite the advantages of the externally-bonded reinforcement on grooves (EBROG) technique in delaying the debonding phenomenon and even its elimination, further studies on the bond behavior of FRP sheet to concrete via this method are needed. In this study, to investigate the effect of groove width and depth variation on the FRP-concrete bond performance and determine the optimal groove dimensions for use in retrofitting, also to validate the related relationships presented in the literature, 28 single-lap shear tests were conducted on 2 EBR and 26 EBROG joint specimens with the average compressive strength of concrete of about 23 MPa, FRP width of 48 mm, and the bond length of 200 mm. Grooves with widths of 2.5, 5, 10, and 15 mm and depths of 2.5, 5, 7.5, 10, and 15 mm were examined. By delaying the FRP separation, the grooving method increased the bond strength in the range of 14.7 to 73.5 % compared to the similar specimens strengthened via the externally -bonded reinforcement (EBR) method. The results showed that between two specimens with the same groove cross-section, the specimen with a larger groove width has a higher bearing capacity compared to the specimen with a larger groove depth. Also, for the groove depths of 5, 10, and 15 mm, the groove widths of 10, 5, and 15 mm showed the highest bond strength, respectively. Moreover, for a given groove width, the optimal groove depth was determined, where increasing the depth beyond this value not only had no effect on increasing the load-bearing capacity of the bond, but also caused a decrease in strength. The results showed that the optimum groove depth for groove widths of 2.5, 5, 10, and 15 mm was 5, 10, 5, and 5 mm, respectively, and the best groove in terms of load-carrying capacity was the groove 10 x 5 mm (width x depth) with a 73.5 % increase in load-carrying capacity compared to the EBR specimen. The results of the experiments were compared with the relationships provided in the literature for the EBROG and EBR methods.