Experimental and Numerical Investigation of Bond and Flexural Behaviour of Additively Manufactured Structural Concrete Beams (2026-02)¶

The extrusion-based 3D concrete printing (3DCP) technique presents distinct material and manufacturing constraints, including the need for smaller aggregate sizes and the development of anisotropy due to layer-by-layer deposition. Moreover, integrating reinforcement within additively manufactured structural concrete (AMSC) remains a major challenge. Wire Arc Additive Manufacturing (WAAM) has emerged as a promising technique for automated steel reinforcement fabrication. This study presents the first experimental investigation into the bond and flexural behaviour of AMSC beams made of printable concrete reinforced with novel WAAM-based 3D-printed rebar (3DPR), supplemented with conventional rebar (CR), followed by the development of a bond–slip model and numerical validation of flexural response. The experimentally obtained bond strength of 3D printed concrete (3DPC) with 3DPR was approximately 20% lower than that of 3DPC with CR, primarily due to the absence of rib-induced mechanical interlocking in 3DPR. The flexural behaviour of AMSC beams reinforced with CR and 3DPR is then evaluated experimentally. Both the AMSC beams reinforced with 3DPR and CR exhibited ductile behaviour, their peak load capacities were limited to approximately 58% and 74% of those of CR-reinforced beams for tensile reinforcement ratios of = 0.5% and = 1.0%, respectively, due to the lower ultimate strength of the printed rebar. Incorporating the bond–slip characteristics, a 3D interface model is proposed to simulate the flexural response of AMSC beams while accounting for the layer-by-layer printing nature of 3DCP. The predictions from the proposed interface model are compared with those of a conventional continuum model and validated against experimental results. The findings show that the proposed 3D interface model can accurately capture both the load-deflection response and the cracking pattern of AMSC beams reinforced with 3DPR. In comparison, the continuum model also predicts the flexural performance of AMSC beams with a fair degree of accuracy. The findings of this study demonstrate the necessity of improved bond modelling and mechanical characterization of AMSC beams for a reliable evaluation of their response.