Effect of Aging on Material Characteristics and Leaching Properties of Incineration Bottom Ash from Municipal Solid Waste

In Japan, approximately 5 million tons of incineration bottom ash (IBA) from municipal solid waste (MSW) is discharged per year. There is serious capacity shortage at the final disposal sites because of limited space. Therefore, IBA as a construction material is being explored. However, since material characteristics of IBA vary due to regional characteristics (e.g., type of waste, volume, place, and season) and also IBA contains significant toxic heavy metals and metalloids (especially lead (Pb), hexavalent chromium (Cr (VI)), cadmium (Cd) and boron (B), and so on), therefore it should be immobilized before it can be used as construction materials. Therefore, it is very important not only to understand the geotechnical characteristics but also to understand the leaching properties. This study examines aging methods to immobilize leachable contaminants in IBA by being exposed to natural precipitation and carbon dioxide from ambient air of landfill (heavy metal contaminants removal by washing and poorly soluble carbonate formation by carbon dioxide). This paper reports the effect of the duration on material characteristics of recycling IBA as a base course material and/or embankment material. As the results, it was revealed that the CBR values of IBA decreases as the number of duration increases. However, there is the potential to use the IBA as a sub-base course material. Also the internal friction angle keeps a certain values irrespective of the number of duration. On the other hands, the cohesion of IBAs decreases with the increase of the duration. Therefore, these behaviors might have affected the compaction characteristics of IBA. However, it was revealed that since IBA has the same strength parameter as general construction material, it can be used as an embankment material. Also the leaching concentrations of heavy metals from IBA were found to be influenced by the aging process. It was revealed that the concentration of Pb, Cr (VI), Cd and B meet the environmental quality standard values for ground material.