Rejuvenation mechanism of cross-linked epoxy resin on aged asphalt: insights from molecular dynamics and rheology

Asphalt recycling represents an advanced, eco-friendly pavement rehabilitation technology where proper rejuvenation of aged asphalt ensures the economic viability of reclaimed asphalt pavement (RAP). In this study, molecular models of raw asphalt and aged asphalt were constructed using Materials Studio. The reaction between the epoxy resin and curing agent was automated via a Perl script, establishing molecular dynamics models of epoxy asphalt and epoxy-aged asphalt containing approximately 30% epoxy resin and achieving a cross-linking rate of 87.5%. Through a dual-method approach-directly analyzing cross-linked epoxy resin's impact on aged asphalt molecules and comparatively evaluating aging degradation in virgin versus epoxy asphalt-we employed cohesive energy density, free volume fraction, and mean square displacement analyses. Results demonstrate that cross-linked epoxy resin weakens strong polar interactions between aged asphalt molecules, increases molecular free volume and diffusion capacity, and significantly inhibits polar molecule aggregation, thereby collectively enhancing aged asphalt performance. Rheological testing confirms that epoxy resin partially restores the viscoelastic properties of aged asphalt, providing macroscopic validation of molecular simulation results. This multi-scale verification advances fundamental understanding of epoxy-recycled asphalt (ERA) systems and establishes theoretical foundations for optimizing pavement performance in sustainable regeneration applications.

To investigate the effect of epoxy polymers on the aging behavior of asphalt, molecular models of virgin asphalt, aged asphalt, epoxy asphalt, and epoxy-aged asphalt were constructed using the Amorphous Cells module of the Materials Studio 2020 software. Molecular dynamics simulations of these four asphalt models were then performed using the Forcite module, with atomic and molecular interactions described by the COMPASS II force field.