Inclined 3D concrete printing: Build-up prediction and early-age performance optimization

To enhance the adaptability of 3D concrete printing (3DCP) to freeform and topologically optimized pre-fabricated structures, it is of great necessity to develop inclined 3D printing for overhang structures. In this study, the prediction criteria for stable buildability of additive stacking was established to facilitate the inclined 3D printing. The optimization of the working performance of 3D printed concrete materials is a prerequisite for achieving rapid construction. Therefore, the approach of compounding retarder and accelerator was simulta-neously adopted to the hybrid cementitious material to optimize the extrudability and early-age stiffness, and furtherly improve the coordination of ultra-early age performance to the additive printing process of overhang structures. The development of green strength of concrete materials are quantitatively analyzed. The optimum replacement rate of HB-CSA to OPC is determined as 15%, and the setting time can be controlled within 35-96 min. Finally, the effectiveness of the developed evaluation method is verified by both the numerical analysis and experimental investigation, the deviation of the proposed constructability evaluation criterion can be controlled within 9.0%.