Multi-material 3D concrete printing: Automated hybrid reinforcements using textile and strain-hardening cementitious composites

3D concrete printing (3DCP) faces challenges in reinforcement integration. This study proposes a multi-material printing strategy incorporating carbon textiles and highly flowable SHCC bonding agents as hybrid reinforcements. A custom three-channel nozzle was developed to enable synchronized mortar deposition and reinforcement placement with a demonstration in the physical world. The effects of textile grid size and reinforcement configuration on flexural performance were evaluated through four-point bending tests. Results showed that, compared to the reference group, the specimen with dense grids (5 mm) achieved a 305.6 % enhancement in flexural strength (from 3.6 MPa to 14.6 MPa) and a 3100 % improvement in ultimate deflection (0.2 mm–6.4 mm), respectively. When the specimen was fully reinforced at every interface, the energy dissipation was 383.3 % higher than that of the specimen only reinforced at the bottom interface. A theoretical model with 87.3 %–95.2 % accuracy was proposed. These findings demonstrate the effectiveness of the proposed strategy in simultaneously enhancing the flexural strength and ductility in 3DCP.