Sustainable Utilization of Bayer Process Red Mud in Subgrade Engineering: A Comprehensive Review on Multi-Scenario Applications, Mechanical Performance, and Environmental Implications

Abstract The disposal of Bayer process red mud (BPRM), a major solid waste from alumina production, is a long-standing environmental concern owing to its high alkalinity and potential for contaminant leaching. While various resource recovery strategies have been explored, its comprehensive utilization rate remains disappointingly low, impeding the green transformation of the aluminum industry. Highway engineering offers a practical solution for its bulk consumption, primarily through two approaches: replacing conventional soil fills in subgrades and enhancing soil properties as a stabilization agent. Recent research has systematically demonstrated the feasibility of these applications, leading to several successful full-scale projects. This paper provides a comprehensive review of this field. It begins by characterizing the properties of BPRM, followed by a detailed discussion on the mechanisms, technical performance, engineering applications, and environmental impacts of various red mud-based subgrade materials, including modified red mud, red mud-based foamed lightweight soil, and red mud-stabilized soil. The review concludes by highlighting the current challenges and proposing future research avenues to advance the resource utilization of red mud in subgrade engineering.