Influence of Infiltration Velocity on the Measurement of the Surface Energy Components of Asphalt Binders Using the Wilhelmy Plate Method

Two common test methods measure the surface energy of asphalt binders: the Wilhelmy plate method and the sessile drop method. In contrast to the sessile drop method, the Wilhelmy plate method introduces the influence of infiltration velocity. As a result, significant differences exist between the Wilhelmy plate method and the sessile drop method in determining the surface energy of the same asphalt binder, despite the fact that the surface energy of the asphalt is constant. To solve the problem caused by infiltration velocity, mathematical models were developed for test samples when the contact angle was obtuse, right, and acute, respectively, to determine the actual dynamic contact angles when considering the influence of infiltration velocity in the Wilhelmy plate method. Based on the relationship between the actual dynamic contact angle and infiltration velocity, a modified Wilhelmy plate calculation method is proposed. The measurements and analyses reflect that the modified Wilhelmy plate calculation method is capable of reducing deviation of asphalt surface energy measured by the Wilhelmy plate method and sessile drop method to less than 10%.