3D printed concrete with red mud incorporation: Influence of red mud manufacturing procedures on mechanical properties at elevated temperatures

3D concrete printing (3DCP) offers formwork-free construction, design flexibility, and potential for solid waste utilization. Red mud (RM), an industrial waste, contains active oxides that enhance hydration and strengthen concrete. However, the variations in RM treatment, dosage, and high-temperature performance remain major challenges for the effective application of RM in 3DCP. This study investigated the influence of manufacturing procedures containing Red Mud Sintering Method (RMSM)and Red Mud Bayer Method (RMBM) in 3D-printed concrete at 10–20 %replacement fraction. Meanwhile, the mechanical performance was evaluated under both ambient conditions and elevated temperatures of 300 °C and 600 °C. In addition, X-ray microtomography (XCT), scanning electron microscopy (SEM), and Digital Image Correlation (DIC) analyses were conducted to investigate the mechanical behavior and microstructure of 3DCP mixtures containing RM. The results indicate that RMSM-based samples outperformed RMBM-based specimens, reaching 57.8 MPa of compressive strength at 10 % replacement. SEM analysis revealed that RMSM mixtures exhibited a denser and more homogeneous microstructure than RMBM mixtures. In terms of high-temperature performance, the RM-0-1 sample achieved the highest compressive strength of 57.8 MPa at 300 °C. XCT analysis confirmed that RMSM-based concrete exhibited a significantly lower porosity of 0.144 % at elevated temperature conditions, indicating enhanced thermal stability. Furthermore, DIC analysis demonstrated that RMSM incorporation improved deformation resistance under ambient conditions and partially mitigated strength reduction at elevated temperatures.