• Achieved 95% total solid waste utilization in backfill material, with red mud at 40 wt%, demonstrating high-volume waste recycling.
• Optimal backfill exhibited 7-day and 28-day compressive strengths of 4.4 MPa and 6.9 MPa, meeting typical underground support requirements.
• Hazardous elements (Ni, Al, Cr6+, As) were effectively immobilized with efficiencies up to 97%, reducing environmental risks.
• The approach offers significant cost savings and carbon emission reductions, promoting sustainable alumina production.