Pavement engineers are constantly using new materials, such as polymer and rubber modified binders, recycled materials, and new types of asphalt mixes, such as open-graded surface courses. With their broader application, concern has been raised about the water quality of surface and subsurface runoff from modified pavement mixes used in the State of California. There are limitations in current worldwide research into runoff water quality regarding which contaminants are directly attributable to the pavement surfacing materials. This research project aims to provide that information, as part of ongoing stormwater runoff management program from the Division of Environmental Analysis of the State of California Department of Transportation (Department).

This controlled experimental study was undertaken by the Department of Civil and Environmental Engineering and the University of California Pavement Research Center (UCPRC) for the California Department of Transportation (Caltrans), Division of Environmental Analysis (DEA). Major focus of the project was to perform laboratory testing of various pavement surfacing materials currently being used by Department and evaluate the water quality of leachate that passed through or over each pavement. Pavement surfacing material tested include: rubberized asphalt concrete-open graded (RAC-O), rubberized asphalt concrete-gap graded (RAC-G), open graded asphalt concrete (OGAC) and Polymer Modified open graded asphalt concrete (OGAC) (two binder sources each for OGAC and polymer modified OGAC, resulting in four different binders), terminal blend modified binder gap graded (MB- G), dense graded asphalt concrete (DGAC), and portland cement concrete (PCC). For each of these 10 pavement materials, 9 specimens will be prepared for testing at three temperatures of 4, 20 and 45 °C and three replicates each. Additionally, one specimen of each asphalt pavement surfacing material was tested to address the influence of age on water quality.