Hydraulic and Environmental Behavior of Recycled Asphalt Pavement in Highway Shoulder Applications

Abstract

Hydraulic conductivity of seven recycled asphalt pavement materials was evaluated through a series of constant head tests, while their leaching potential was determined through batch water leach tests and column leach tests. The contaminant transport in surface waters as a function of distance was numerically simulated. Laboratory test results indicated that the hydraulic conductivity of recycled asphalt pavement is comparable to that of the natural aggregate with the gradation of clean sand-gravel mixture as it ranged from 6.89x10-3 cm/s to 1.14x10-2 cm/s. The amounts of all metals released during the water leach tests were below the water quality limits, except for copper. Column leach tests yielded generally low or non-detectable metal concentrations. The deviation from this trend occurred for Cu and Zn concentrations, but they fell below the regulatory limits at 4 and 0.5 pore volumes of flow, respectively. Finally, concentrations of metals conformed to the water quality standards in surface waters after passing through the natural formation.