Volume 2, Issue 5 (May 2005)
Evaluation of Different Techniques for Adhesive Properties of Asphalt-Filler Systems at Interfacial Region
Asphalt is a widely variable product used in public roadways at the rate of 30 million tons per year and is thus the largest volume of adhesive used in any application. Considering the commercial importance of asphalt, several analytical techniques were employed to investigate its adhesive properties. These techniques include the specially designed sliding plate viscometer, differential scanning calorimetry (DSC), atomic force microscopy (AFM), liquid chromatography, centrifugation, and infrared (IR) spectroscopy. The specially designed sliding plate rheometer was used to measure the rheological properties of asphalt film in contact with aggregate surface at thin film levels. DSC was applied to measure the effect of fine particles on the low temperature properties. AFM was used to produce a photo-like image of adhesion between asphalt and mineral fines. Chromatography and centrifugation techniques were used to separate the adsorbable, polar asphalt components from aggregate surfaces. Infrared spectroscopy was used to determine the quantities and natures of adsorbed molecules. The results of these asphalt-aggregate experiments have shown what types of organic molecules in asphalt adsorb onto aggregate surfaces. Aggregates are shown to adsorb large concentrations of the most polar functional groups found in asphalts. In addition, the theory of Interfacial Morphological Stability has been used to model air-asphalt film and asphalt film-glass substrate interfacial systems. Separately, a wet-packing chromatographic technique was developed to use pulverized aggregate to separate cyclohexane solutions of asphalt into polar and non-polar components. Furthermore, the DSC evidence suggests the immobilization of a surface layer of binder in contact with aggregate induces a large rigid, amorphous fraction of the binder. These methods have been employed to characterize the fundamentals of asphalt-aggregate interaction in order to devise improved road performance predictive tests.