Leaching of Pollutants from Reclaimed Asphalt Pavement

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Abstract
The construction and expansion of asphalt roadways results in the production of a large amount of milled asphalt also known as reclaimed asphalt pavement (RAP). A major fraction of this RAP is recycled by incorporation into a new asphalt mixture. At times, however, a large amount of this material may require other forms of management. One proposed alternative for the management of RAP is use as fill material. A limitation to using RAP as fill material stems from unknown risks of pollutants leaching from the waste to the environment. Research was conducted to address some of the environmental concerns related to the possible leaching of pollutants from RAP. Six samples of RAP was collected from asphalt plants throughout Florida. A series of leaching tests were performed at both batch-scale and in leaching columns. The primary chemicals investigated were volatile organic compounds (VOCs), polycyclic aromatic hydrocarbons (PAHs), and heavy metals. Results from the Toxicity Characteristic and the Synthetic Precipitation Leaching Procedures (both batch tests) indicated that the RAP samples investigated were not a hazardous waste and did not leach chemicals greater than typical groundwater standards. Leachate collected during the column studies did not contain levels of PAHs, VOCs, or selected heavy metals (Ba, Ca, Cr, Cu, Ni, and Zn) above typical groundwater regulatory concentrations. In RAP from older roadways, lead was detected in amounts slightly above the primary drinking water standard (15 μg/L), but the concentration diminished over time. Key words: Asphalt; reclaimed asphalt pavement (RAP); leachate; toxicity characteristic leaching procedure (TCLP); synthetic precipitation leaching procedure (SPLP); polycyclic aromatic hydrocarbons (PAHs); lysimeter columns; batch test