Surface free energy and moisture susceptibility evaluation of asphalt binders modified with surfactant-based chemical additive

Warm mix additives are used to lower the production and application temperature of asphalt mixtures. Moisture damage is one of the main reported issues with warm mix asphalt due to its lower production temperature and the possible presence of moisture being trapped during the mixing process. This paper considers the use surface free energy evaluation as a fundamental material property to assess mixture performance. Cecabase® chemical surfactant additive was used to prepare warm mix asphalt binders. Contact angle measurements were determined with a Goniometer to evaluate surface free energy measures such as work of adhesion, work of debonding and compatibility ratio. The results show that the use of the surfactant-based additive reduces surface free energy. It increases after short-term (Rolling Thin Film Oven) and reduces after long-term (Pressure Aging Vessel) aging. The analytical measurements based on surface free energy results illustrate that the surfactant-based warm mix additive improves the spreadibility of asphalt binder over the aggregate particles. The work of adhesion slightly improves with the addition of Cecabase® content. Compatibility ratio is an indicator of moisture susceptibility and indicates that the granite aggregates are less resistant to moisture damage compared to the limestone aggregates used in this laboratory study.