Design of 3D printing green ultra-high performance concrete based on binder system optimization

The technology of 3D-printed concrete is receiving considerable attention, yet its advancement is impeded by the preparation of printing materials. Low cement ultra-high performance concrete (LC-UHPC) is a promising material for 3D printing due to its excellent mechanical properties, low shrinkage, low environmental impact, and excellent durability. To inform the design of LC-UHPC suitable for 3D printing, this study presents a systematic investigation of the influence of binder material composition on printability, shrinkage, mechanical properties, and environmental impact. Moreover, the hydration, mechanical properties, and microstructure of the designed 3D-printed LC-UHPC are examined. The printability and mechanical performance of ultra-high performance concrete (UHPC) can be enhanced through the utilization of a reduced cement content. The correlation between binder material composition and printability has been determined. The incorporation of an appropriate quantity of nano-silica can result in further improvement in the printability and mechanical properties of LC-UHPC. It bears note that LC-UHPC exhibits an impressive 45.2 % reduction in carbon emissions. Furthermore, it displays superior volume stability, as evidenced by the fact that drying shrinkage deformation occurs at only 70 % of the levels observed in ordinary UHPC. The degree of cement hydration of 3D-printed LC-UHPC is 57 % higher than that of UHPC. At the 28-day age, the 3D-printed LC-UHPC displays a superior pore structure in comparison to UHPC.