Experimental study on iron ore tailings sand and municipal solid waste incineration fly ash used in semi-rigid base of asphalt pavement

•A solution that can eliminate IOT and MSWI fly ash in large quantities and effectively is investigated.•The washed MSWI fly ash together with IOT demonstrated a better performance.•Heavy metals in MSWI fly ash cannot pollute environment after solidification. In order to co-dispose and effectively utilize the bulk solid waste of iron ore tailings (IOT) sand and hazardous solid waste of municipal solid waste incineration (MSWI) fly ash, a study on using them in pavement base course is carried out in this paper. In this work, cement and fly ash (with a ratio of 1:3) were used as stabilizing materials. IOT was used as aggregate, while MSWI fly ash was used as a part of the cementitious material or as a partial replacement for the aggregate in the road base. The samples were tested for unconfined compressive strength, indirect tensile strength, drying shrinkage, temperature shrinkage and toxicity leaching. XRD and SEM-EDS were also used to analyze the changes in structure and properties. The results showed that the samples incorporated with washed ash instead of IOT had greater strength development. The unconfined compressive strength of the unconstrained samples decreased after partially replacing cement and fly ash. At the same time, the drying shrinkage rate became larger compared to the group without adding MSWI fly ash. The leaching results of toxic substances showed that most of the lead and zinc contents were easily diffused into the environment. However, after cement hardening, the leaching rate of various heavy metals was significantly reduced, which was far below the threshold of national standards.