Bitumen Surface Energy Characterization Using a Contact Angle Approach

TLDR

Quantifying adhesion via surface energies of bitumen and aggregates is essential for selecting compatible materials and assessing moisture susceptibility; reliable characterization is needed, and contact‑angle measurements with various liquids are a proven method, but incorrect probe selection or data interpretation can mislead. The study refines a test method and analysis procedure to estimate bitumen surface energy. The refined method uses Wilhelmy plate contact‑angle measurements to calculate bitumen surface energy. The method yields contact‑angle based surface energies for five neat and three modified bitumen, revealing correlations with hot mix asphalt damage, and earlier work showed that combining these energies with aggregate energies accurately predicts moisture susceptibility. Related work by Bhasin et al.

Abstract

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.