Interfacial bonding performance of 3D-printed Ultra-High Performance Strain-Hardening Cementitious Composites (UHP-SHCC) and cast normal concrete

Using 3D-printed elements as permanent formwork for structural members is an efficient way to integrate 3D printing technology in the traditional construction field which could also enhance structural capacity and possibly address the reinforcement challenge during 3D concrete printing. The bonding performance between 3D-printed formwork and post-cast concrete is crucial for maintaining the overall mechanical performance of the structures. This study experimentally investigates the interfacial bonding properties between 3D-printed Ultra-High Performance Strain-Hardening Cementitious Composites (UHP-SHCC) permanent formwork and post-cast normal concrete (NC). Three groups of prismatic composite specimens with smooth, grooved, and 3D-printed interfaces are subjected to the splitting tensile test to evaluate the interfacial bonding. A fully cast normal concrete specimen is also tested as a reference for comparison. The failure modes, splitting tensile strength, and effective bonding area ratio of normal concrete are analyzed and discussed. Results reveal that the splitting tensile strength of interfaces with grooved and 3D-printed preparation is significantly higher than that of the smooth interface, with an increase of 92.2%-114.8 %.