An experimental investigation on the bond behavior of steel reinforced polymers on concrete substrate

Steel Reinforced Polymer (SRP) systems have recently emerged as an attractive solution for the external strengthening of reinforced concrete structures. They entail unidirectional fabrics made out of high tensile strength steel cords that can be externally bonded to the substrate via wet lay-up, using either epoxy or polyester resin. Currently, research about the behavior of SRP strengthening systems for concrete structures is evolving but further systematic and comprehensive studies are still needed to ensure the consistency and reliability of the studies performed to date. The present paper contributes to expanding the existing knowledge by presenting the results of an extensive experimental program devoted to investigate the bond behaviour between SRP and concrete substrate. To this purpose, a number of SRP strips were bonded to concrete blocks by a thixotropic organic matrix and the lap joint was subsequently subjected to direct shear tests performed in displacement control. Besides the concrete strength, the following study parameters were considered: (a) the concrete surface roughness in the bonded region, (b) the density of the steel fabric, (c) the ratio of the epoxy covered concrete surface width to the SRP strip width, and (d) the bonded interface length.