Targeted Enhancement Strategy for the Rebar Interface Bond in 3D Printed Coarse Aggregate Concrete: Performance Evaluation and Mechanistic Insights (2026-02)¶

The implantation of rebar into 3D printed concrete inevitably induces macroscopic pores at the interface, severely degrading bond performance. Targeting these process-induced defects, this study proposes a novel targeted enhancement strategy utilizing expansive cement mortar (ECM). It systematically evaluates the enhancement efficacy of ECM versus common mortar (CM) across reinforced 3D printed concrete systems containing coarse aggregates (recycled/natural) and mortar-only mixtures. The results indicate that ECM, beyond merely filling pores, fundamentally reconstructed the interfacial stress transfer path. This strategy enhanced the tensile and shear bond strengths of the reinforced interface in 3D printed recycled coarse aggregate concrete by 111.0% and 36.2%, respectively, demonstrating a significant superiority over the CM treatment. By establishing a predictive model correlating pore defects with bond performance, this work provides mechanistic insights and a targeted solution to the inherent conflict between rebar reinforcement and process-induced interfacial defects.