Sustainable palm oil fuel ash mortar used as partial adhesive replacement in flexurally strengthened RC beams

Structural strengthening comprises modification of the structural elements to enhance their load bearing capability, stiffness, toughness, and ductility. The present study is an experimental investigation on the performance of reinforced concrete (RC) beam specimens strengthened by the side near surface mounted (SNSM) technique with reinforcement strengthening of glass fiber reinforced polymer (GFRP) bars in flexure. Sustainable palm oil fuel ash (POFA) mortar (PM) and normal mortar were used as bonding mediators between the concrete substrate and GFRP bars as a replacement for epoxy adhesive. A total of eight specimens, in which one was a control, one was strengthened by GFRP bars and full epoxy adhesive in grooves, and six specimens were strengthened by GFRP bars and partial replacement of epoxy adhesive by PM and NM, respectively. The specimens were tested in the static condition under four-point bending. During the test, the loads, deflection, and strains of the specimens were stored in a data logger and the failure modes of the specimens were observed. Critical discussions were made based on the flexural capacities, load-deflection, ductility, energy absorption, the influence of epoxy replacement and the type of mortars in the strengthened specimens as compared to the control specimen. ACI 440.2R-08 and ACI 318-11 were applied to predict the ultimate load-carrying capacity and deflection characteristic graphs of the tested specimens. The predicted results of the specimens were in close agreement with the experimental results. The test results also exhibited that the epoxy substituted by sustainable PM had superior flexural performance to the NM strengthened SNSM-GFRP bar specimens, particularly when considering the economic and eco-friendly viewpoint.