Experimental Study on the Bar Selection and Interfacial Bond Performance for 3D Printing Concrete

To investigate the bond performance between bars and 3D printed concrete,this study prepared 33 central pull-out specimens to analyze the influence of bar surface treatment,bar texture,and bar diameter on the bond performance.The results indicate that with an increase in bar rib height,the interfacial bond mechanism changes,transitioning from bar pull-out failure to concrete splitting or bar fracture failure.The bond strength of deep-ribbed GFRP specimens increased by 292% compared to that of shallow-ribbed GFRP specimens,and the bond strength of deep-ribbed steel specimens increased by 95% compared to that of plain round steel specimens.Small-diameter shallow-ribbed FRP specimens mostly experienced pull-out failure,while large-diameter deep-ribbed steel specimens tended to experience splitting failure.Additionally,the applicability of existing bar-concrete interface bond stress-slip constitutive models to the bar-3D printed concrete interface was analyzed,and the key parameters of the models were calibrated.Finally,based on the data from this study and existing literature,a discernible and physically meaningful equation for distinguishing the failure mode of bond interface between FRP/steel bars and 3D printed concrete was proposed,providing reference for subsequent bar selection in 3D printed concrete structures.