In the present study, fly ash waste materials were tested along with quicklime (CaO) as an effective, yet economic technology to immobilize Pb, as well as Cr~(+3) and Cr~(+6) present in contaminated clayey sand soils. The degree of heavy metal stabilization was evaluated using the Toxicity Characteristic Leaching Procedure (TCLP) as well as other controlled extraction experiments. These leaching test results along with X-ray diffraction (XRD), scanning electron microscope and energy dispersive x-ray (SEM-EDX) analyses were also implemented to elucidate the mechanisms responsible for heavy metal immobilization. Furthermore, the reuse potential of the stabilized waste forms was also investigated by performing unconfined compressive strength (UCS) and swed tests. Addition of fly ash along with quicklime to the contaminated soils effectively reduces heavy metal leachability well below the non-hazardous regulatory limits. Meanwhile, it significantly improves the stress-strain properties of the treated solids, thus allowing their reuse as readily available construction materials. The results presented herein can be applied to the management of incinerator and coal fly ash, boiler slag and flue gas desulfurization wastes.
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