Bitumen Surface Energy Characterization Using a Contact Angle Approach

The ability to quantify adhesion based on surface energies of the bitumen and aggregate components enables selection of compatible materials and quantitative assessment of moisture susceptibility. Reliable surface energy characterization is required in order to implement this technology successfully. One proven method to estimate bitumen surface energy is to calculate it using contact angles measured with various liquids. However, improper selection of probe liquids or interpretation of resulting data can easily mislead users into drawing inaccurate conclusions. This paper presents a refined test method and analysis procedure customized to estimate bitumen surface energy using contact angles measured by the Wilhelmy plate. Results for five neat and three modified bitumen are presented and results are interpreted to study the relationships between contact-angle based surface energies and damage in hot mix asphalt. In a separate study by Bhasin et al. in 2004, surface energy characteristics of bitumen determined using methods described in this paper were combined with surface energies of aggregates to successfully predict moisture susceptibility of mixes.