Development of strain-hardening cementitious composites (SHCC) as bonding materials to enhance interlayer and flexural performance of 3D printed concrete

3D concrete printing (3DCP) has limitations in weak interlayer bond strength and reinforcement integration. To tackle these challenges, this study aims to develop and deposit strain-hardening cementitious composites (SHCC) as bonding materials between layers for simultaneous enhancement of interlayer bond strength and flexural ductility of 3D-printed concrete. The impact of rheological properties of SHCC materials and configurations of SHCC layers on multi-layer printed structures were investigated experimentally and theoretically. Results show an increase in interlayer bond strength by approximately 80 % compared to the reference without SHCC interlayers. Microstructure characterization reveals that the SHCC bonding material effectively reduces the interfacial porosity by nearly 35 %. Four-point bending was adopted to evaluate flexural strength, ductility, and fracture properties. With SHCC interlayers, flexural hardening behavior was attained with an increase in flexural strength, deflection, and energy absorption capacity by approximately 25 %, 180 %, and 800 %, respectively. Furthermore, a theoretical model was proposed to predict flexural strength with nearly 95 % accuracy. The findings reveal that the newly developed printing scheme has the potential to address both reinforcement and weak interlayer problems in 3DCP.