Bauxite Residue-Based 3D Printing Mortar (2025-09)¶

Produced in massive quantities across the world, bauxite residue (BR) is an underutilized solid waste with serious environmental implications. Aiming for more efficient BR utilization, this study introduces a paste replacement approach into 3D printing mortar for the first time. In this approach, BR replaces part of the paste (water + cement) without changing the water-to-cement ratio, and a water reducer is used to regulate the mixture’s workability. The results indicate that BR-based mortars achieve optimal printability metrics based on this approach. Concurrently, the use of BR as a paste replacement demonstrates multifaceted enhancements, including strength improvement (up to 16.8 %), refined packing density, optimized microstructure, and accelerated hydration kinetics, while achieving significant reductions in cement consumption (maximum 10.0 %) and carbon emissions (peak reduction 9.6 %). Mechanistically, these benefits originate from the synergistic interplay between lowered equivalent water-to-cement ratio, enhanced packing density, and precise water reducer dosage control. Furthermore, the cementing efficiency factor of BR was determined to be 0.739, and a high-precision model for compressive strength was formulated. Finally, the proposed eco-efficiency indices (strength-cement ratio, strength-carbon ratio and strength-cost ratio) collectively validate that the paste replacement strategy provides a scalable technical pathway for productive utilization of industrial solid wastes and development of environmentally-friendly, economical construction materials.