Bond behavior of H-shaped steel embedded in recycled aggregate concrete under push-out loads

Twenty two push-out tests were carried out in order to investigate the bond behavior between H-shaped steel and recycled aggregate concrete (RAC). Eleven kinds of recycled coarse aggregate (RCA) replacement ratios (i.e., 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%) were designed in the test, and considering different categories of bond position of H-shaped steel, concrete protective cover thickness, stirrup reinforcement ratio, source and size of RCA were also selected. The load-slip curves at the loading end and free end were obtained; in addition, the distribution of H-shaped steel strain and the bond stress along the embedded length were analyzed. The bond strength in this investigation is related to the RAC cube compressive strength, and as a result, the interface bonding increases with RCA replacement ratio increasing. The bond strengths between different parts of H-shaped steel and RAC can be disparate: (1) the largest bond stress is located at the inside interface of the flange of H-shaped steel; (2) the second one is on the outside interface of the flange of H-shaped steel; (3) the bond stress between web of H-shaped steel and recycled coarse aggregate concrete is the smallest. What’s more, it was found that the ultimate and residual bond stresses can be enlarged due to the stronger grip action with increasing of concrete protective cover thickness and larger constrained effect with expanding the stirrup reinforcement ratio. The RCA serving age has a negative effect on the bonding performance, and when the size of RCA reduces, the ultimate bond strength decreases accordingly. Finally, four calculation models applied to predict the bond strength for all the specimens and the component of bond stress between shape steel and RAC is derived through the law of periodic transmission.