Investigation of the Adhesion and Debonding Behaviors between Warm-Mix Recycled Asphalt and Aggregates Based on Molecular Dynamics Simulation

Abstract

Warm-mix recycling technology has gained increasing adoption in practical engineering owing to its notable environmental and economic advantages. Nevertheless, the intricate interfacial mechanisms governing the interaction between asphalt and aggregate during the reprocessing process remain unclear. The objective of this study is to investigate the adhesion and debonding behaviors between warm-mix recycled asphalt and aggregates through the utilization of molecular dynamics simulation. Molecular models representing the asphalt-aggregate interface in four different states (virgin, long-term aged, recycled, and warm-mix recycled) were developed to assess the interaction effects between various asphalt binders and aggregates. The aggregation of asphalt components under both dry and humid conditions was evaluated using mean square displacement and molecular radial distribution function. Furthermore, the debonding behaviors of different asphalt-aggregate interfaces were analyzed by defining the adhesion energy. The findings indicate that aging enhances the aggregation behavior of the molecular structure while diminishing the contact area and molecular activity between the asphalt binder and aggregate. Although the compound regenerant fails to fully degrade the oxidation functional groups in aged asphalt, it effectively penetrates and fills the intermolecular aggregation spaces, thereby increasing the contact area and molecular activity between the asphalt and aggregate. The warm-mix regeneration process primarily enhances the activity of lightweight components to improve adhesion between the aged asphalt and aggregates. The present study provides a certain research basis for the microinterface mechanism between warm-mix recycled asphalt-aggregate.