Study on the synergistic effects and eco-friendly performance of red mud-based quaternary cementitious materials

Abstract

Red mud, as the primary byproduct of processing bauxite into aluminum, raises environmental concerns due to its significant alkalinity and substantial heavy metal content. Addressing the limitations of traditional methods, this study proposes an innovative solution to utilize red mud, steel slag, fly ash, and phosphogypsum together to produce a new type of low-carbon, environmentally friendly cementitious material. Utilizing advanced techniques such as X-ray diffraction, thermogravimetric analysis, Fourier-transform infrared spectroscopy, mercury intrusion porosimetry, and scanning electron microscopy with energy-dispersive spectroscopy, this study conducted a comprehensive evaluation of cementitious materials, revealing their synergistic mechanisms. Furthermore, artificial neural networks and genetic algorithms were employed to optimize the mix ratio of the quaternary binder, aiming to predict and enhance the material's mechanical strength. Research shows that quaternary cementitious materials outperform traditional binary and ternary materials in compressive strength, hydration properties, microstructure, and environmental performance. Particularly, the increased content of calcium-aluminate-silicate-hydrate and sodium-calcium-silicate-aluminate-hydrate gels and a denser matrix structure highlight the synergistic effect in the hydration reaction of the quaternary system. Through mix proportion optimization, a significant enhancement in compressive strength up to 21.4 MPa is achieved. Environmental assessment shows that the composite material effectively solidifies Na+, with non-renewable resource and energy consumption reduced by 84.7% and 83.8%, respectively, compared to traditional cement, highlighting its environmental and energy-saving advantages. This approach addresses red mud storage, produces green building materials that meet standards, and fulfills resource and environmental goals.