Effects of Pore Defects on Interfacial Bonding Between Rebar and 3D Printed Coarse Aggregate Concrete Under Multiple Loading Conditions (2026-01)¶

Reinforcement integration in 3D printed concrete (3DPC) creates complex interfacial microstructures that critically govern printed structural performance. This study systematically investigates the bond behavior between rebar and 3D printed natural coarse aggregate concrete (3DPNAC) under multiple loading conditions, with particular emphasis on process-induced interconnected pore defects. Comparative analysis demonstrates that coarse aggregates enhance interlayer tensile and shear strengths by 57.6 % and 70.3 %, respectively, through improved fracture tortuosity and mechanical interlocking. However, rebar placement generates interconnected pore networks that severely compromise interfacial load transfer, resulting in pronounced anisotropic bond-slip behavior (parallel > vertical >45° orientation). A novel rebar-3DPNAC interface structural zoning framework is proposed, which establishes explicit processing-structure-property relationships and reveals the fundamental conflict between pore-induced weakening and aggregate-induced strengthening at rebar-concrete interfaces. The findings provide critical mechanistic insights for optimizing reinforcement strategies in 3DPC structures, bridging the gap between material-level understanding and structural design requirements.