Modeling the Oxidative Aging Kinetics and Pathways of Asphalt: A ReaxFF Molecular Dynamics Study

Abstract

The ReaxFF molecular dynamics simulations, which can predict chemical reactions, were performed on integral asphalt and individual asphalt molecules at different temperatures and oxygen levels to investigate the oxidation mechanism of asphalt and develop a molecular model suitable for aged asphalt. The simulation of integral asphalt suggests that the main oxidation products of asphalt are C–O, H–O, and S–O bonds. The oxygen level has the greatest influence on the yield of C–O bonds, and the temperature has the greatest influence on the H–O bonds. The simulation of individual asphalt molecules indicated that the oxidation of asphalt is accompanied by the decomposition of the aromatic rings, and thus, the aromaticity of the oxidized asphalt is decreased. Oxidation of asphaltenes starts with the oxygen molecules attacking the aromatic ring and generating a ketone, while the initial reactions of the other components are diverse. In addition, the simulation results were validated with Fourier transform infrared spectroscopy and nuclear magnetic resonance tests and were used to study the effects of oxidation on the characteristics of asphalt. The results suggested that the introduction of oxygen-containing functional groups decreases the component compatibility of asphalt and causes the aged asphalt to be harder and more viscous.

A Review on Multiscale Modeling of Asphalt: Development and Applications

“…Furthermore, ReaxFF, as a bond-orderdependent forcefield, has been used to investigate the oxidation mechanism and the self-healing behaviors of asphalt [148]. Experimental measurements have verified the results of Reactive MD simulations, and the obtained asphalt model is also considered valid [149].…”

Reactive molecular dynamics study of the oxidation behavior of iron‐based alloy in supercritical water

“…The ReaxFF method is an empirical force field, which is developed to bridge the gap between the quantum mechanical (QM) method and experiment. [26] The ReaxFF method is several orders of magnitude faster than QM simulation, which allows fully reactive atomic-scale MD simulations of chemical reactions. Considering its accuracy and low computational expense, the ReaxFF method is applied to evaluate the FeCr-H 2 O reaction system in this paper.…”

“…Re-axFF reactive MD simulations bridge the gap between first-principles empirical force-field methods, which could conduct large simulations and maintain a high accuracy. [25][26][27] The ReaxFF can simulate chemical reactions at the interface and provide a reasonable description of atom-exchange dynamics. [27,28] The success of ReaxFF Reactive MD simulations depends critically on the fidelity of interatomic potentials.…”

Mini-Review on the Application of Nanomaterials in Improving Anti-Aging Properties of Asphalt

“…As an important component of asphalt pavement, asphalt material bonds loose aggregate into a whole after compaction . However, after aging, the brittleness of asphalt material increases, and the adhesive strength between asphalt and aggregates decreases. , It makes asphalt easy to peel from the surface of aggregates, causing pavement distress such as looseness and peeling. − Furthermore, the increasing brittleness of asphalt could reduce the tensile strength and fatigue resistance of asphalt concrete. , Consequently, asphalt pavement is prone to cracking in low-temperature environments or under repeated loading. Further, the generation of cracking greatly increases the risk of water infiltration into the pavement structure.…”