Evaluating surface energy components of asphalt binders using Wilhelmy Plate and Sessile Drop Techniques

In this Study, the surface energy was investigated for six penetration grade 70/100 bitumen binders. Wilhelmy Plate and the Sessile Drop were used to determine the contact angles. The purpose of this study was to compare the Wilhelmy Plate method with the Sessile Drop method, and to compare the significance of Owens-Wendt model with the significance of Acid Base model by correlating surface energy components. Better R2 –values were found for surface energy components by using the Owens-Wendt model than by using the Acid Base model. It was concluded here that Owens-Wendt model is a better model for determining surface energy components of bituminous binders than the Acid Base model since bituminous binders have low energy surfaces. For both instruments: When using Diiodomethane as a probe liquid the biggest variations among the binders were observed. When using water as a probe liquid the least variations among the binders were observed. The advancing contact angles for water determined for these six bitumen binders using the Wilhelmy plate method do not exceed the 90 degree by much, suggesting that bitumen is not extremely hydrophobic. The Sessile Drop method offers a faster and more convenient way to measure the surface energy components of bitumen binders than the Wilhelmy Plate method.