Fly ash produced by power plants in the United States occasionally contains significant amountsof unburned carbon due to the use of low nitrogen-oxide and sulphur-oxide burners in recentyears. This ash cannot be reused in concrete production due to its reactivity with air entrainmentadmixtures and is largely placed in landfills. Roadways have high potential for large volume useof high carbon fly ash (HCFA). HCFA can be activated with lime kiln dust (a disposed residue oflime production plants) and used as the base layer for newly paved roads. However, in suchapplications, the leaching of heavy metals from fly ash-stabilized base layers can causesignificant environmental concerns. A series of column leach tests (CLTs) were conducted toinvestigate the leaching potential of chromium (Cr) from the fly ash-stabilized soils. The resultsindicate that an increase in LKD amount, pH, and fly ash content have significant effects onleaching behavior of heavy metals from soil-fly ash mixtures. The leaching of Cr in CLTsexhibited a first flush pattern, and the concentrations quickly decreased to below EPA maximumconcentration limits (MCLs) for drinking waters. In addition, a groundwater contaminationmodeling computer program (WiscLEACH) was used to estimate the Cr concentrations atdifferent depths and distances from the center alignment of the center of the HCFA stabilizedbase layer.
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