Research on the Regulation of Rheological Properties of 3D Printed Recycled Concrete and Multi-Objective Optimization of Printer Parameters (2026-02)¶

The technology of 3D printed recycled aggregate concrete (3DPRAC) offers dual benefits by advancing the intelligent transformation of the construction industry and promoting sustainable development, which has garnered considerable research interest. This study first investigated the effects of resting time and recycled fine aggregate (RFA) replacement rate on the fluidity of 3DPRAC through fluidity tests, and explored the regulatory mechanisms of its rheological properties. The correlation between fluidity and both buildability and mechanical performance was established, with the underlying mechanisms further elucidated via microstructural analysis. Subsequently, response surface methodology (RSM) was employed to systematically examine the influence of key printing parameters, including extrusion speed, horizontal printing speed, and vertical movement speed, on the material's performance. Through multi-objective optimization, an optimal parameter combination was identified. The results demonstrate that controlling the fluidity within 160–180 mm enables stable shaping without collapse, achieving a buildability height of up to 205 mm. Moreover, under the optimized parameters, namely an extrusion speed of 0.77 r/s, a horizontal printing speed of 40.8 mm/s, and a vertical movement speed of 10.3 mm/s, the material exhibits superior printing quality and structural stability, with both buildability and mechanical performance reaching their optimum. This study provides a theoretical basis and technical support for the engineering application of 3DPRAC.