Mechanical properties and environmental characteristics of the synergistic preparation of cementitious materials using electrolytic manganese residue, steel slag, and blast furnace slag

The high content of heavy metals in electrolytic manganese residue (EMR) makes it difficult to utilize in engineering, and direct disposal can pose a threat to the environment. This study uses EMR as a raw material combined with steel slag (SS) and blast furnace slag (GGBS) to prepare electrolytic manganese residue-based cementitious material (ESGM) under the action of an alkali activator (NaOH), and studies the effects of the EMR to SS ratio and alkali activator concentration on the flowability, setting time, compressive strength, and toxic leaching of ESGM. In addition, XRD, FTIR, SEMEDS, and MIP were used to study the microscopic characteristics of ESGM and its stabilization/solidification mechanism for heavy metals. The results indicate that an increase in EMR content will reduce the fluidity and setting time of the slurry, while an increase in alkali activator concentration will increase the fluidity of the slurry and reduce the setting time. When the content of EMR, SS, and GGBS is 50%, 20%, and 30%, respectively, and the concentration of alkali activator is 0.2, the strength of ESGM reaches its maximum, reaching 23.0 MPa in 28 days. The heavy metal leaching in ESGM is lower than the allowable range of Chinese standard GB 89781–996, and the material meets environmental requirements. The microscopic analysis showed that the ESGM gelling products were mainly C-(A)-S-H and N-A-S-H gels, and the formation of ettringite was also observed. Mn2+ in EMR was mainly stabilized in ESGM in the form of MnO2 and H2Mn8O16·2.4 H2O.