Experimental and theoretical study on bonding performance of FRP bars-Recycled aggregate concrete

Abstract

Fiber Reinforced Polymer (FRP) bars-Recycled Aggregate Concrete (RAC) can alleviate the environmental damage caused by the massive exploitation of natural aggregates and solve the problem of corrosion of steel bars in concrete structures. However, the bonding performance of FRP bars-RAC determines whether it can replace the original reinforced concrete structure in buildings. In the current study, FRP bars-RAC bond performance factors and bond strength theory have been comprehensively investigated through pull-out tests performed for a large number of FRP bars-RAC. In this context, the effects of Recycled Aggregate (RA) replacement rate (0 %, 25 %, 50 % and 100 %), FRP bar diameter (8 mm, 10 mm and 12 mm) and RAC cover thickness (20 mm, 30 mm, 40 mm and 70 mm) on the bond strength, fracture mode, and bond-slip curve of FRP bars-RAC were investigated. Overall, the findings showed that the inclusion of RA reduces the ductility of concrete. Increasing the recycled aggregate replacement rate resulted in gradual losses in bond strength and ultimate slip of FRP bars. In addition, the increase in the diameter and anchor length of the FRP bars led to a gradual decrease in the bond strength between the FRP bars and the RAC. Nevertheless, through increasing the strength of RAC and the thickness of the concrete protective layer, the bond strength between FRP bars-RAC can be enhanced. Through the analysis of test data, the bond strength model of FRP bars-RAC was established based on the thick-walled cylinder theory. In the model, the diameters of FRP bars, rib inclination angle, rib spacing, RAC strength, and protective layer thickness were taken as variables. While the high degree of agreement between the values calculated from the model and the measured values revealed the success of the established modeling, the ratio of the calculated value of the model to the experimental value was measured as 0.66–1.