Utilization of red mud in high-performance grouting material for semi-flexible pavement

The huge amount of red mud has brought great challenges to the sustainability of global economic development. Red mud, a solid waste, causes resource wastage and environmental pollution, even endangering human health. A technology used to overcome such a situation involves broad-scale recycling of red mud in road engineering. In this study, Bayer red mud is utilized as a high-performance grouting material for semi-flexible pavement (SFP). A series of sensitivity analyses are performed using macroscale testing to determine the optimal amount of red mud and water-cement ratio for red mud-based cementitious materials (RCM) grouting material. This includes alkali-activated “red mud-slag powder” binary cementitious material (RSCM) and non-alkali-activated “red mud-cement” cementitious material (RCCM). Additionally, the hydration process and products of RCM are analyzed using microscale testing, including scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The results of the analysis indicate that red mud has significant potential for recycling as SFP materials to achieve the goal of high fluidity and early strength. The workability and early strength of RCCM are even higher than those of cement, indicating that part of the cement can be replaced by red mud. Moreover, the macroscale conclusions of RCM can be confirmed by microscale testing. These low-carbon grouting materials offer the added advantages of recycling waste that would otherwise be destined for landfill, along with reducing the carbon footprint and economic impact associated with cement production.