Influence of Recycling Agent on Surface Free Energy of Asphalt Cement

Abstract

Reliable surface free energy characterization is required in order to implement the suitable recycling agent into aged asphalt. One proven method to estimate asphalt surface free energy is to calculate it using contact angles measured with various liquids. The efficiency of recycling agent in terms of its impact on rheology and surface free energy of asphalt cement is vital in the decision of recycling aged asphalt concrete. In this investigation, asphalt cement of penetration grade 40-50 was subjected to aging using the thin film oven test. The aged and the control asphalt cement samples have been digested with various percentages of two type of polymer recycling agents (Polyethylene and crumb rubber). Recycled and control asphalt cement specimens were subjected to physical and rheological properties determination, while the surface free energy was determined using Wilhelmy plate and Sessile drop methods. It was observed that the surface free energy decreases after aging, while it increases after digestion with polymers. Digestion of aged asphalt cement with polyethylene was able to retain the original surface free energy of asphalt cement before aging, while a higher percentage of 1.5 polyethylene has improved the surface free energy beyond the requirements. Digestion of aged asphalt cement with crumb rubber was able to increase the surface free energy of asphalt cement by one-fold of that before aging when Wilhelmy plate method was implemented, while a higher percentage of 1.0 of crumb rubber has improved the surface free energy beyond the requirements.

Modeling the Influence of Surface Free Energy on Moisture Damage of Recycled Asphalt Concrete

“…The surface free energy was calculated using the mathematical models presented by Little and Bhasin, (2006). Details of the testing and test results were published elsewhere, Sarsam and Hamdan, (2019).…”