Experimental and analytical investigation on the bond of SRP systems to concrete

Steel Reinforced Polymer (SRP) systems have recently emerged as attractive solutions for external strengthening and repairing of existing structures. Experimental studies have frequently shown the potentials of these innovative composite systems in improving the performance of concrete and masonry structures. However, additional studies are needed to expand the existing knowledge and either to provide design recommendations or to develop specific guidelines. The paper fills some of the foregoing knowledge gaps by discussing the experimental results of 130 direct single-lap shear tests performed to investigate the bond behavior between the SRP reinforcement and the concrete substrate; different concrete surface finishes were investigated, i.e., sandblasted, bush hammered and grinded which are among the surface treatments mostly used in practice. Comparisons between the maximum load resisted by the SRP-concrete joints and the theoretical value calculated using some relationships available for similar FRP-concrete assemblages are discussed. Then, the experimental results relative to SRP-concrete joints with sandblasted finish were used to: a) calibrate the parameters of some bond-slip interface models available in the literature for FRP-concrete interface, and b) compare the obtained relationships with the interface models proposed in a previous study for SRP-concrete joints with bush-hammered and grinded concrete surface finish only. The bond-slip models calibrated for the three considered concrete surfaces were finally used to develop theoretical relationships between the maximum bond stress in the steel strip at debonding and the concrete strength. Comparisons with the experimental data were also performed.