Factors affecting the flexural performance of reinforced 3D printed concrete beams

3D Concrete Printing (3DCP) has the potential to support the adoption of digital manufacturing approaches in construction. However, applications are currently limited by the lack of understanding of the structural performance of elements manufactured with this process. The layer-wise fabrication process enables the placement of reinforcement between printed layers. The final reinforcement position depends on the fresh properties of wet material. Moreover, toolpath strategies influence the cross-sectional geometry and concrete anisotropic compressive strength. Understanding the relative importance of these factors as they relate to the mechanical performance of the printed concrete becomes, therefore, critical for 3DCP use. This study addresses this gap through experimental and numerical studies of the flexural behaviour of 3DCP beams with different reinforcement positions and toolpath strategies. The results demonstrate that the toolpath orientation, and hence anisotropy, can be neglected for the cases explored here. Moreover, toolpath orientations perpendicular to the steel reinforcement reduce the risk of shear and delamination failure as cracks align with the vertical interface, thus promoting flexural cracking. The position of the steel reinforcement is the most significant factor: specimens printed with reinforcement closer to the top layers showed increased flexural performance if compared with those printed with the reinforcement closer to the bottom layers. • Reinforcement reduces the effect of anisotropy, which can be potentially neglected in flexural loading. • Cross-sectional geometry of 3D printed concrete beams varies with toolpath strategies. • Concrete cover and effective depth vary with layer placement. • The final position of reinforcement is the most influential factor affecting flexural performance.