Role of rejuvenator properties in determining the activation effects on aged asphalt based on molecular simulations

Activating the aromatic aggregates by rejuvenators is essential to improve asphalt performance but sufficient understanding is further needed. This study provides a method to evaluate the activation state of aromatic aggregates and the activation effect of rejuvenators on asphalt performance through molecular simulations. Herein, seven types of aromatic aggregation are investigated to obtain representative types by measuring the number of monomers in aggregates at large aggregation determination distances to characterize the aggregates. Solvent accessible surface area is used to examine the aggregates at close distances. Thus, the activation state of aggregates and the effect of rejuvenators are determined. The activation mechanism of rejuvenators on their affinity to aggregates is clarified by radial distribution function (RDF) and interaction energy. Activation efficiency is evaluated by the diffusion coefficient. Viscosity and tensile properties are used to represent asphalt performance. Results show that asphaltenes and resins constitute the aggregate cores, and the aggregation of resins and aromatics determines the expansion of each core. The dispersion and expansion of aggregate cores contribute to forming the aggregation network in the asphalt system, which determines tensile properties and is enhanced by rejuvenators of plasticizer type. A less or weak network resulting from rejuvenators of saturated structures tends to improve the activation efficiency and viscosity. In addition, these activation effects of rejuvenators are determined by their interactions with asphalt fractions as revealed by RDF and energy results.