Assessing Moisture Damage of Asphalt-Aggregate Systems Using Principles of Thermodynamics: Effects of Recycled Materials and Binder Aging

Abstract

This study utilized the concept of surface free energy to assess the effect of binder aging, types of aggregate, and recycled mineral fillers on the moisture susceptibility of asphalt-aggregate systems. A total of 12 combinations of asphalt mastic and aggregates were evaluated. The surface free energy for each mastic type was determined based on contact angle measurements obtained using the sessile drop method. Next, the work of adhesion and the work of debonding for all combinations of asphalt mastics and aggregates were quantified based on their surface free energy components. The energy ratio parameter was used to assess the resistance to moisture damage of each mastic-aggregate combination. Moreover, mixes with different asphalt aging conditions—nonaged, short-term aged, and long-term aged—were evaluated to determine the effect of asphalt aging on moisture susceptibility. The results confirmed that limestone aggregates are less susceptible to moisture damage than granite aggregates. Furthermore, the use of recycled mineral fillers, mainly from recycled concrete aggregates (RCA) and recycled asphalt pavement (RAP), significantly reduces the resistance of asphalt-aggregate systems to moisture damage. Last, the results revealed that asphalt-aggregate systems become less able to resist moisture damage as the asphalt ages.