Reuse of incinerator fly ash in soft soil stabilization

One of the ways in which highly urbanized cities cope with increasing amounts of municipal solid waste (MSW) generated by the population is incineration. As land is a very precious commodity and landfills are fast dwindling in most highly urbanized cities, the disposal of the ash generated from MSW incineration poses increasingly difficult problems for the municipalities. A viable solution to the disposal problems would be the reuse of MSW ash for civil engineering applications. A research study of the properties of the incinerator fly ash derived from MSW incineration indicated that fly ash is a potential source of jet-grouting admixture for soil improvement. The fly ash exhibits a likelihood of pozzolanic reaction due to its chemical composition and physical characteristics. The use of fly ash as an admixture in the stabilization of a soft marine clay resulted in stabilized samples with an improved strength more than 75 times that of the untreated clay. Incorporation of fly ash also improved drainage property by at least one order of magnitude and reduced both the plasticity and compression indices by about 69 and 23%, respectively. Leachate investigation conducted on the fly ash-stabilized soils indicated that chromium was well-below the World Health Organization drinking water limit, while nickel and lead were in excess of the limits. The nickel and lead leachate concentrations diminished to below the acceptable drinking water limits over a period of about 130 and 110 days, respectively.