Experimental and finite element study on bond behavior between GFRP bar and recycled aggregate concrete

Fiber Reinforced Polymer (FRP) bars are a type of reinforcement material characterized by high tensile strength and corrosion resistance. Substituting steel bars in Recycled Aggregate Concrete (RAC) structures with FRP bars can significantly enhance the durability of these structures. The effective bond performance between the FRP bars and RAC is the foundation for their composite action. Accordingly, this paper presents a study on the pull-out tests of Glass Fiber Reinforced Polymer (GFRP) bars embedded in RAC. The study investigates the effects of various parameters on the bonding properties, including bond strength, bond-slip curve, and stress distribution within the concrete. The parameters considered are the Recycled Aggregate (RA) replacement rate, the compressive strength of the RAC, and the cover thickness of the RAC. The results indicate that bond strength diminishes as the RA replacement rate increases, while it improves with higher RAC strength and greater cover thickness. The tangential stress transfer patterns in RAC exhibit general similarities, transitioning from compressive stress in the early loading stage to tensile stress during the middle stage of loading. Based on the experiments, numerical simulations are performed using ABAQUS finite element software, and the validity of the model is verified in terms of failure modes, bond-slip curves, tangential strain on the RAC surface of specimens, and bond strength. Subsequently, the effects of RA replacement rate, GFRP bar diameter, and anchorage length on bond strength under various RAC strength grades were examined. Combining the experimental and numerical simulation results, the theoretical model for bond strength proposed by Liu is refined, introducing an anchorage length influence coefficient. The enhanced theoretical model of bond strength between FRP bars and RAC demonstrated calculated values closely matching the measured values, with errors generally maintained within ±15 %. •Influence of various factors on the bond behavior between GFRP bar-RAC was investigated.•A precise finite element model approach for deep-thread GFRP bar-RAC was developed.•An enhanced theoretical model for predicting bond strength was proposed.