Production of quasi-sulfoaluminate cementitious materials with electrolytic manganese residue
Electrolytic manganese residue (EMR) is a harmful solid industrial waste that comes from the electrolytic manganese industry and has rarely been recycled in large quantities. To consume as much EMR as possible, quasi-sulfoaluminate cementitious material (Q-SAC) was prepared by firing high amounts of EMR together with limestone and kaolin at approximately 1200 °C (∼50–100 °C lower than that of ordinary sulfoaluminate cement). The major crystalline phases of Q-SAC determined by XRD were calcium sulfoaluminate, dicalcium silicate and calcium sulfate. The final setting times of Q-SAC were less than half an hour. The early and long-term alkalinities of Q-SAC pastes were approximately 2 and 1 lower than those of OPC paste, respectively. The results also showed that Q-SAC prepared by mixing 10–40% of EMR can obtain compressive strength of 35–65 MPa at 56 days. When 5% of gypsum was added, the early and long-term strengths of Q-SAC were approximately 50% and 30% higher, respectively. The results showed that the use of EMR for Q-SAC production is a promising way to recycle EMR because of its low firing temperature and good mechanical performance.