A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Leaching of Contaminants from Recycled Asphalt Pavement used in Highway Construction(2017) Seybou Insa, Ousmane; Aydilek, Ahmet H; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Recycled asphalt pavement (RAP) is a material resulting the removal and reprocessing of the existing asphalt pavement. Annually, more than 80 million tons of RAP is produced in the United States. Most of the RAP is landfilled, which constitutes a significant economic burden and a waste of landfill space. RAP has great potential in highway construction due to its good physical properties. However, concerns have been raised due to potential surface water and groundwater contamination by metals including some heavy metals and Polycyclic Aromatic Hydrocarbons (PAHs) present in RAP. A series of batch-level pH-dependent leaching tests and Toxicity Characteristics Leaching Procedure (TCLP) tests were conducted to investigate the leaching of metals from seven RAPs collected across the state of Maryland. The results of the pH-dependent leaching tests indicated As to be slightly above the U.S EPA Water Quality Limit (WQL). The results of a series of TCLP tests showed that two PAHs, chrysene and Indeno[1,2,3-cd]pyrene, may be present in the leachates, albeit, at concentrations very comparable to those leach from a new asphalt material. The results of the geochemical modeling indicated that the leached metals were solubility-controlled. Oxide and hydroxide minerals control the leaching of Al and Fe; whereas, leaching of Ba, Ca and Mg were controlled by carbonate and/or sulfate minerals.Item Evaluation of Leaching Protocols for the Testing of Coal Combustion Byproducts(2010) Becker, Jason Louis; Aydilek, Ahmet; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Beneficial reuse of coal combustion byproducts requires an evaluation of metal leaching potential. Reuse of high carbon fly ash in highway embankment construction was evaluated using different soil-fly ash mixtures and three common leaching tests: the water leach test (WLT), the Toxicity Characteristic Leaching Procedure (TCLP), and the column leach test (CLT). The effect of test methodology and pH on Cu, As, and Cr leaching was examined. TCLP concentrations for Cu and As exceeded those from WLTs in the majority of mixtures due to lower pH conditions, while Cr was higher in the WLT for alkaline fly ash mixtures. Peak CLT concentrations were higher than TCLP and WLT concentrations for the majority of mixtures, but usually decreased rapidly, suggesting that leachate concentrations might exceed regulatory limits, but only for a short time. Based on these results, a combined WLT and CLT leaching protocol for testing fly ash mixtures is presented.Item Release of inorganic and organic contaminants from fly ash amended permeable reactive barriers(2008-01-25) Morar, Doina Lorena; Aydilek, Ahmet H.; Seagren, Eric A.; Civil Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Large quantities of fly ash are generated in the United States via coal combustion, most of which is disposed of in lagoons or landfills. The overall goal of this research was to assess the feasibility of using high carbon content (HCC) fly ashes as a reactive medium in permeable reactive barriers (PRBs) for remediation of petroleum hydrocarbon contaminated groundwater. A series of column and batch tests were performed to evaluate the leaching of selected metals from the fly ash, and adsorption/desorption of two target hydrocarbons (naphthalene and o-xylene) onto/from this PRB medium. Leaching of metals in the column experiments exhibited a first-flush, followed by a tailing slope elution pattern for all fly ashes. The naphthalene and o-xylene adsorption/desorption on/from the fly ashes were directly correlated with the organic carbon of the fly ash as measured by loss in ignition. Adsorption/desorption hysteresis was obvious in column and batch tests, suggesting that the adsorption/desorption was not completely reversible during the testing.