Trace Metal Leaching from Embankment Soils Amended with High-Carbon Fly Ash: Fid-Bau Portal

Trace Metal Leaching from Embankment Soils Amended with High-Carbon Fly Ash

Cetin, Bora / Aydilek, Ahmet H. / Li, Lin

Abstract

The use of fly ash in highway applications as a stabilizing agent and soil amendment for embankments has become very common owing to its economical advantages. However, fly ash may contain toxic constituents that may pose environmental risk if they leach through the soil and reach groundwater. A series of water leach tests (WLTs), toxicity characteristic leaching procedure (TCLP) tests, and column leach tests (CLTs) were conducted to define the leaching of aluminum, arsenic, chromium, and zinc from a self-cementitious fly ash and four different off-spec high-carbon ashes. Laboratory results indicated that an increase in fly ash contents generally yields an increase in pH and leached metal concentrations regardless of the type of fly ash and metals. Furthermore, it was determined that there were significant differences in the leached metal concentrations measured in the three different laboratory tests, i.e., $C_{CLT} > C_{TCLP} > C_{WLT}$ . Analyses conducted using a numerical groundwater model indicated that predicted field metal concentrations for the mixtures prepared with high-carbon fly ash were generally lower than the concentrations measured in the laboratory and decreased to concentration levels that do not possess any environmental risk.