Inverse Gas–Liquid Chromatography Study of Asphalt Composition and Oxidative Aging

The chemical composition of an asphalt binder significantly affects oxidative aging and interactions with both aggregate and binder modifiers. In turn, it may cause premature asphalt pavement failures through fatigue cracking, moisture damage, or other failure mechanisms. Analytical chemical procedures, such as ion exchange chromatography, are time-consuming and cost prohibitive as routine tests. Inverse gas–liquid chromatography (IGLC) is a relatively faster and simpler technique that provides the chemical composition and polarity characteristics of asphalt samples. In IGLC, asphalt is used as the liquid substrate on an inert support in a GLC column and is characterized by measuring the retention behavior of selected test compounds that possess different functional groups. The interaction behaviors between seven test compounds and 19 unaged and GLC column–aged asphalt samples were determined and compared with functional group concentrations presented in the asphalts and in a nonaqueous potentiometric titration study. It was found that the retention behaviors of the test compounds are strongly related to the types and concentrations of functional groups in the asphalt. For unaged asphalts, the retention behavior of strongly basic test compounds is highly correlated with the concentration of acidic functional groups in asphalts. The retention behavior of phenol with oxidatively aged asphalts is highly correlated with the concentration of sulfoxide, one of the major products of asphalt oxidation.