Simulation of colloidal aggregate structure in asphalt using dissipative particle dynamics

The colloidal structure of asphalt plays a crucial role in determining mechanical and rheological properties, with asphaltene aggregation significantly affecting stability and performance. This study utilizes dissipative particle dynamics (DPD) simulations to explore the effects of the chemical composition and content of the four main components—saturates, aromatics, resins, and asphaltenes (SARA)—on the aggregation behavior of asphaltenes, offering a novel approach to understanding microstructural regulation in asphalt systems. Coarse-grained models were constructed, and aggregation metrics, including the degree of aggregation (A_degree) and aggregate composition, were analyzed. The results show a strong positive correlation between asphaltene content and A_degree, while resins act as stabilizers, reducing aggregation. Variations in the chemical composition of asphaltenes reveal that asphaltene-phenol promotes aggregation, whereas asphaltene-pyrrole disperses it. Resin molecules such as trimethylbenzeneoxane and benzobisbenzothiophe exhibit contrasting effects on aggregation due to differences in self-interaction and adsorption capacities. Although aromatics and saturates have a minimal influence on A_degree, they significantly regulate aggregate composition, especially in promoting medium and large aggregates. These findings provide new insights into the molecular interactions governing the colloidal stability of asphalt, offering theoretical guidance for optimizing the composition of SARA fractions.