Low-carbon ternary precursor alkali-activated road subbase materials derived from industrial solid wastes: Synergistic utilization of red mud, molybdenum tailings and iron tailings.

Industrial solid-waste-based alkali-activated materials offer a practical route to lower the environmental impacts of ordinary Portland cement manufacture and promote circular resource use. In this study, red mud (RM), ground granulated blast furnace slag (GGBS), molybdenum tailings (MoT), and iron tailings (IT) were synergistically valorized to develop a low-carbon alkali-activated material for sustainable infrastructure applications. A three-factor orthogonal scheme was used to optimize the RM to GGBS mass ratio, NaOH dosage, and MoT content. Reaction mechanisms and phase evolution were systematically elucidated using XRD, SEM, FT-IR, and TG-DTG analyses. Based on the optimized binder composition (RM to GGBS mass ratio = 3:7, NaOH = 5%, MoT = 15%), iron tailings were stabilized to produce Alkali-activated road construction materials (ARCM). Increasing the binder to sand ratio generally enhanced mechanical performance, bearing capacity, and resistance to environmental actions while reducing carbonation depth. A multi-criteria decision analysis integrating entropy weight and grey relational analysis identified ARCM-18 as the optimal mix-ratio group, which was further validated through field application. Cradle-to-gate life cycle assessment showed that ARCM-18 reduced CO2 emissions by more than 50% compared with the selected conventional cement stabilized and geopolymer based road subbase materials while retaining economic advantages. The findings demonstrate the potential of synergistic multi-waste utilization for developing low-carbon and resource efficient road infrastructure.