Abstract:
In this study, an analytic method was developed for detecting potential oil contaminants in asphalt mixtures using gel permeation chromatography (GPC) and Fourier-transform infrared spectroscopy (FTIR). This study was initiated when the authors were contacted by a major contractor whose field crew reported spots of loose asphalt pavement and suspected the pavement surface was being contaminated with spills of petroleum-based oils or other soluble chemicals. Oil contamination would change the content and performance grade of the asphalt binder in the mixture, thus compromising the properties and performance of the asphalt pavement. The proposed method involved extracting asphalt binders from potentially contaminated asphalt mixtures using the solvent tetrahydrofuran (THF), testing the extracted binders using GPC and FTIR, and comparing their results with those of the pure asphalt binder and oil contaminants. This study first verified the proposed method by testing artificially contaminated asphalt binders at different contamination contents and then evaluated seven potentially contaminated asphalt mixtures from the job site, as well as six possible oil contaminants. The study shows that the GPC results yielded convincing evidence whether or not asphalt mixtures were contaminated and that the FTIR results were effective in detecting specific oil contaminants using their characteristic peaks.
