Investigation on Bond-Slip Performance of Steel Rebar Embedded in Concrete Confined by 3D Concrete Printing Formwork (2026-01)¶

Due to the weakness of concrete’s tensile properties, reinforcement is required for 3D concrete printing (3DCP) structures. Among all methods, the one of steel rebar reinforced concrete confined by 3DCP formwork shows potential without affecting the design flexibility. However, investigations on the bond-slip performance of the steel rebar embedded into concrete confined by 3DCP formwork (SR3DPF) are limited. Moreover, despite 3DCP formwork as the permanent formwork, it remains unclear whether it can work as a normal concrete cover to offer confinement for embedded steel rebar. To fill these gaps, the bond-slip performance of steel rebar in normal concrete without 3DCP formwork (SRCANP) and SR3DPF was studied experimentally and numerically. Pull-out test results showed that the bond strength of SR3DPF is lower than that of SRCANP, even though 3DCP concrete is stronger than cast concrete, suggesting that 3DCP formwork cannot work as the normal concrete cover. Through combining simulation and pull-out test results, it was determined that the low bond strength of SR3DPF was attributed to the poor interfacial bond between cast concrete and 3DCP formwork. Additionally, simulation results revealed that besides improving interfacial mechanical properties, enhancing the mechanical properties of cast concrete and increasing the proportion of cast concrete in the concrete cover can benefit the bond strength of SR3DPF.