Durability and hardened properties of 3D printed concrete containing bauxite tailings

This study aims to investigate the effect of bauxite tailings as fine aggregate instead of natural sand on the durability and hardened properties of 3D printed concrete (3DPC). Firstly, the durability and hardened properties of 3DPC were evaluated. Subsequently, various experiments including hydration heat, pore structure, nanoindentation, thermogravimetric analysis and SEM tests were performed to explore the influence mechanism of tailings on 3DPC. The results reveal that 3DPC containing tailings exhibits superior mechanical properties compared with T0 (without tailings), during both the early and later stages of development. The addition of tailings enhances the resistance to chloride ion attack and carbonation of 3DPC, but weakens its resistance to drying shrinkage. The ending time of the induction period and the time required to reach the second exothermic peak are shorter for T35 (with 35 % replacement of tailings) compared to T0, while T35 demonstrates a higher cumulative heat release than T0. In addition, T35 has a denser interface transition zone of 3DPC compared to T0 due to the pozzolanic activity and crystalline nucleation effect of the tailings. Furthermore, the incorporation of bauxite tailings enhances the compactness between natural aggregate and cement paste. In conclusion, this study elucidates the influence mechanism of bauxite tailings on the durability and hardened properties of 3DPC, providing a theoretical basis for the application of bauxite tailings in construction materials.