Thermodynamic simulation-assisted design of the electrolytic manganese residue-slag-Ca(OH)2 cementitious system: Reaction and Mn immobilization

The disposal of electrolytic manganese residue (EMR) is a critical challenge. This study introduces an EMR-blast furnace slag-Ca(OH) 2 cementitious system (EG CH ), utilizing the gypsum in EMR to activate the slag to form a product resembling a supersulfated cement. With up to 40 % EMR incorporation, it achieves compressive strengths of 16.8 MPa at 3 d and 33.2 MPa at 28 days. The primary reaction products are AFt, C-A-S-H and hydrotalcite. A thermodynamic simulation-assisted iterative calculation was developed and validated by pore solution analysis, to accurately quantify phase evolution. EMR content significantly influences the reaction and results in distinct exothermic profiles. The optimal 40 % EMR content results in the densest microstructure due to the balanced formation of AFt and C-A-S-H. Mn is immobilized in EG CH with two barriers to its leaching and cannot leach out until the pH drops below 7. This binder offers a practical solution for the utilization of EMR.