# Study of factors affecting the blend of virgin and aged asphalt binder based on molecular dynamics simulation

## TL;DR

This study uses molecular dynamics simulations to analyze how virgin and aged asphalt binders blend in recycled asphalt mixtures, identifying key factors that influence their blending behavior.

## Contribution

A novel blend model with a rejuvenator system and molecular dynamics simulations to study the microscopic blending mechanisms of asphalt binders.

## Key findings

- The degree of blending increased with rejuvenator content up to 15%, after which it slightly decreased.
- Blending improved with longer simulation time and higher temperature.
- Aged asphalt content negatively affected blending, and simulation time was the most influential factor.

## Abstract

To understand the blending behavior of virgin and aged asphalt binder in thermally recycled asphalt mixtures, a series of studies on the blending behavior of virgin and aged asphalt based on molecular dynamics simulations have been performed. A blend model was developed for virgin asphalt binder and aged asphalt binder with rejuvenator system, which is saturated with 12 different molecules. In-depth analysis of microscopic blending mechanisms through the effects of rejuvenator content, simulation time, temperature and aged asphalt binder content on the degree of blending of virgin and aged asphalt binder. Using Materials Studio, the blend of virgin and aged asphalt binder under different conditions was quantitatively analyzed. It was found that the degree of blending of virgin and aged asphalt increased gradually with the content of rejuvenator, but the degree of blending decreased slightly when increased to 15%. The degree of blending gradually increased with the increase of time and also with the increase of temperature during the simulation time of 2000 ps. In terms of aged asphalt content, the degree of blending of virgin and aged asphalt gradually decreased with the increase of aged asphalt content. And through the fitting analysis found that the order of correlation between the four factors and the degree of blending was: simulation time > aged asphalt content > temperature > rejuvenator content. To verify the reliability of the results of the molecular dynamics simulation, the performance of recycled asphalt was verified using the asphalt rheological properties test (DSR) and the three major indexes (needle penetration, softening point, and ductility) tests. The results of the combined rheological property test and the three major index tests were found to be consistent with the order of influence of the four factors obtained in the molecular dynamics simulation. Therefore, it can be concluded that the use of molecular dynamics simulation in this study to analyze the blend behavior of virgin and aged asphalt in recycled asphalt is relatively accurate.