Synergistic effect of iron tailings, steel slag and red mud cementitious materials on Mechanical and microstructure properties

Abstract

Utilizing industrial solid waste for cementitious materials addresses ecological environmental pollution, and contributes significantly to reducing carbon emission, thus fostering sustainable development. The cementitious materials were prepared using three types of solid waste: red mud (RM), iron tailings (IR) and steel slag (SS) in this study. The impact of the synergistic interaction between RM-IR-SS on the mechanical properties was investigated. Additionally, the hydration products were characterized by X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), thermogravimetry derivative thermogravimetry (TG) and Scanning Electron Microscopy (SEM). The results showed that the optimum strength reached 11.83 MPa after curing 28 d with a composition of 30% RM, 40% IR, 30% SS a solid-liquid ratio of 0.35 and an alkaline activator module of 1.30. RM was found to be rich in OH-, which formed an alkaline solution upon contact with water. This solution, in interaction with alkaline activators, effectively dissolved large amount of Si and Al substances from RM, IR and SS. The dissolved Na+, Ca2+, [Al(OH)6]3-, [H3SiO4]-, [H3AlO4]2-, and OH- reacted to generate ettringite, C-S-H, and C(N)-A-S-H gels. The diffusion of these gel and ettringite, coupled with the reduction of porosity, formed a dense matrix structure, which improved the mechanical properties. The research establishes a solid foundation for the optimal utilization of alkali, calcareous, and silica-aluminum solid waste, further contributing to a more sustainable industrial ecosystem through their synergistic utilization as building materials.