Preparation of road base material by utilizing electrolytic manganese residue based on Si-Al structure: Mechanical properties and Mn2+ stabilization/solidification characterization.

Electrolytic manganese residue (EMR) is a potentially harmful industrial solid waste that should be addressed. In the study, the red mud, carbide slag and blast furnace slag were used as stabilization/solidification (S/S) agents to S/S Mn2+, and simultaneous reused it as raw material to prepare road base material. The S/S behavior of manganese, unconfined compressive strength (UCS) of road base material with different Al/Si ratios, leaching test and the S/S mechanisms were investigated. The results showed that the Mn2+ can be well solidified when the S/S agents reach up to 20 %. The 7-day UCS of the road base material was 6.1 MPa with the Al/Si ratio of 0.48, which meets the highway standards. When Al/Si = 0.48, the formation amount of CaAl2Si2O8·4H2O and ettringite increased, which promoted the adsorption and wrap of Mn2+. The content of active AlⅣ and AlⅥ increased after S/S. Mn2SiO4 and Ca4Mn4Si8O24 were produced by the charge balance effect, and the new chemical bond was formed. Meanwhile, the Mn2+ is oxidized to more stable MnO2 to achieve the S/S of Mn2+. This research provides an effective way to solidify Mn2+ and solves the problem of large-scale utilization of EMR and other solid waste.