COOEE bitumen. Chemical aging

TL;DR

This study uses molecular dynamics simulations to investigate chemical aging in COOEE bitumen, revealing how aging causes molecular aggregation and dynamics slowdown, with detailed insights into molecular roles.

Contribution

It introduces a molecular simulation model for COOEE bitumen to analyze chemical aging and its effects on molecular dynamics and aggregation behaviors.

Findings

Aging significantly slows molecular dynamics.

Asphaltene aggregation increases with aging.

Different molecule types have distinct roles in aging.

Abstract

We study chemical aging in "COOEE bitumen" using molecular dynamic simulations. This model bitumen is composed of four realistic molecule types: saturated hydrocarbon, resinous oil, resin, and asphaltene. The aging reaction is modelled by the chemical reaction: "2 resins $\rightarrow$ 1 asphaltene". Molecular dynamic simulations of four bitumen compositions, obtained by a repeated application of the aging reaction, are performed. The stress autocorrelation function, the fluid structure, the rotational dynamics of the plane aromatic molecules, and the diffusivity of each molecule, are determined for the four different compositions. The aging reaction causes a significant dynamics slowdown, which is correlated to the aggregation of asphaltene molecules in larger and dynamically slower nanoaggregates. Finally, a detailed description of the role of each molecule types in the aggregation and aging processes is given.