Exploring the deagglomerating behaviors of selected additives on oxidized asphaltenes using the steered molecular dynamics approach

Abstract

Recycling agent plays an increasingly important role in promoting asphalt pavement sustainability, as it allows to bump up the incorporating dosage of recycled asphalt materials. The desired characteristics of a recycling agent includes not only the softening effect but also the capability of deagglomerating the oxidized asphaltenes by effectively interacting with them. The objective of this study was to provide novel insights into the deagglomerating potential of three additives selected based on the structural and compositional discrepancies, including an aromatic extract C12H16, a bio-additive myristamide C14H29NO, and a common plasticizer tributyl citrate (TBC) C18H32O7. Steered molecular dynamics simulation was performed to obtain the intercalation in which each additive was intercalated between the stacking asphaltene sheets, with the objective to simulate the outcome of blending and mixing. These configurations were then subjected to long-time simulations during which the structural changes and the interactions were tracked. The results indicated that the aromatic extract yielded the least impact on the asphaltene dimer configuration during intercalation and had little deagglomerating effectiveness. Owing to the higher molecular flexibility and polarity, the other two additives produced more pronounced changes in the dimer structure during intercalation. They were able to disintegrate the dimer by exfoliating off and separating an asphaltene monomer, even though the effects were only temporary before re-dimerization occurred. Different types of interactions of the additives with the asphaltenes were visualized based on quantum chemical computations and discussed with respect to their contributions to the deagglomerating behaviors.