Limits on Adhesive Bond Energy for Improved Resistance of Hot-Mix Asphalt to Moisture Damage

TLDR

The loss of physical adhesion between aggregate and asphalt binder is a key mechanism accelerating moisture damage in hot‑mix asphalt pavements. The study quantifies two bond‑energy parameters—adhesive bond energy and free‑energy reduction upon moisture‑induced debonding—using surface energies of aggregate and asphalt. Thresholds for these parameters were derived by comparing them to field performance data across several mixes, and binders from different sources with the same performance grade were evaluated. Significant differences in bond energies across aggregate–binder combinations were observed, underscoring the importance of binder‑aggregate compatibility and the sensitivity of bond strength to surface energy measurements.

Abstract

The loss of physical adhesion between the aggregate and the asphalt binder is one of the important mechanisms that accelerate moisture damage in hot-mix asphalt pavements. In this study, two parameters related to bond energy—adhesive bond energy between the aggregate and the asphalt and reduction of free energy when asphalt debonds from the aggregate surface in the presence of moisture—were quantified with surface energies of both materials. Threshold values of these parameters to identify asphalt-aggregate combinations susceptible to premature moisture damage were derived by comparison of the values of these parameters with observed field performance for several mixes. Results show significant differences in bond energies developed between various aggregates and a given binder. This finding illustrates the importance of binder-aggregate compatibility and the sensitivity of calculated bond strength to surface energy measurements. Asphalt binders from different sources with the same performance grade were ...