Dynamic Contact Angle (DCA) Analyzer in Dr.O'Rear's lab is used to measure the angle of contact between the asphalt binder film and a probe liquid. The DCA analyzer uses a WINDCA software to precisely record the change in mass of the sample while immersing it into and withdrawing from the probe liquid. The results are processed to determine the contact angle: advancing contact angle during advancing and receding contact angle during withdrawing. Advancing contact angle, as per Young-Dupre postulate, can be used to calculate the Surface Free Energy (SFE) components of the asphalt binder, namely acid SFE, base SFE, Lifshitz-van der Waals SFE, acid-based SFE, and total SFE. The SFE components are further used to quantify the wettability, adhesion and debonding of the asphalt binder from aggregates.
For sample preparation, a 25 mm x 50 mm standard glass plate is dipped in the liquefied asphalt binder preheated to a certain temperature such as 145°C. The plate is kept vertically in the oven to get a thin-film of the asphalt binder. Finally, the plate is placed in a desiccator overnight. Usually, DCA with three probe liquids such as water, glycerin, and formamide is required to determine the SFE components.