Saddle Stitching-Enabled Interfacial Toughening in 3D Printed Concrete (2025-09)¶

Reinforcement implantation in concrete 3D printing is always a challenging task. Herein, a saddle stitching reinforcement (SSR) was developed to reinforce 3D printed concrete (3DPC). Compression and splitting tests were conducted to evaluate the mechanical properties of SSR-3DPC with anisotropy assessment; digital image correlation (DIC) analysis was integrated to track the failure process and mode; and X-ray computed tomography (XCT) was employed to characterize the interfacial microstructure of stitched 3DPC specimens and quantitatively analyze defects. Results demonstrate that the proposed saddle stitching technique effectively mitigates the splitting strength anisotropy, and enhances the slipping strength, ductility, and absorption energy through the combined action of stitch legs and crotch reinforcement. However, a weaker interface between stitches and concrete matrix occurs due to the inadequate self-recovery of 3DPC slurries after implantation. These findings deepen the understanding of reinforcement implantation in viscous concrete slurries, and provide valuable insights for optimizing reinforcement strategies in concrete 3D printing.