Steel Slag-Red Mud-Based Multi-solid Waste Pavement Base Material: Preparation, Properties and Microstructure Study

Steel slag (SS) and red mud (RM) are hazardous solid wastes that require disposal. In this work, SS-RM-based multi-solid waste composite pavement base material (PBM) was proposed based on different Ca/(Si + Al) ratios. Its performance, structure and toxicity leaching have been studied. The microstructure was characterized by XRD, SEM-EDS, Si-29 MAS NMR and MIP analysis. The results showed that the SS-3 had the greatest unconfined compressive strength after 7 days of maintenance when Ca/(Si + Al) was 1.20. Simultaneously, the best CBR value and shrinkage properties were also obtained by SS-3. The microscopic products of the PBM were C-A-S-H gel, AFt and Na2Al2Si3O10 center dot 2H(2)O, which were beneficial to the strength improvement. The best polymerization degree of Si-Al and the pore structure were also obtained by SS-3. The leaching results showed that Na+ and other heavy metals could be well solidified. SS-RM based PBM provided theoretical guidance for the application of solid waste in large quantities.