Reuse of Fly Ash–Amended Petroleum-Contaminated Soils in Highway Embankments

Abstract

Remediation of contaminated soil and groundwater has been an important task for engineers and scientists in recent years. One of the sources of soil and groundwater contamination in the United States is petroleum spills. A laboratory study evaluated the geotechnical engineering properties and environmental suitability of remediated petroleum-contaminated soils for their possible use in highway construction. The laboratory test program included compaction, batch sorption, and long-term column leaching tests. Diesel fuel, naphthalene, and a model nonaqueous phase liquid (NAPL) were used as the pollutants; waste coal fly ash that included high carbon content was used to stabilize the contaminated soils. Compaction test results indicated that the maximum unit weights and optimum liquid contents of the stabilized soils satisfy the limits set for highway embankment construction. The results of the batch-scale adsorption tests conducted on the fly ash revealed that the ash has good naphthalene sorption properties because of the presence of high carbon content in its structure. Column leaching test results suggested that the naphthalene and o-xylene concentrations in the effluents collected from the fly ash–stabilized specimens were lower than those collected from the control specimens (i.e., borrow material). The findings indicate that the high carbon content fly ashes can be good sorptive agents for remediation of petroleum contaminated soils because of their low cost and presence of high carbon content. However, caution should be exercised when the laboratory results are carried to field conditions, because the level of contamination is likely to influence the leaching properties.