The Rejuvenating Potential of Plasticizers on Oxidatively Aged Asphalts: Rheological and Molecular Dynamics Perspectives

Recycle and reuse of waste asphalt materials in the pavement industry has brought tremendous contributions to the infrastructure sustainability and environmental preservation. The recent literature has suggested a great potential of plasticizers to be used for rejuvenating the oxidated paving asphalts. This study was aimed at assessing the rejuvenating effectiveness by rheological characterizations of two typical plasticizers, dibutyl phthalate (DBP) and tributyl citrate (TBC), selected based on the molecular structural differences. The underlying rejuvenating mechanisms were approached using molecular dynamics (MD) simulation, for probing the interactions between the plasticizers and oxidized asphaltenes and examining the outcomes in terms of deagglomeration. The results indicated that both plasticizers were highly effective in restoring the stiffness and elasticity properties as well as fatigue resistance of the aged asphalt. According to the simulations, the two plasticizers were able to deagglomerate the asphaltene associations. Owing to the high polarity and hydroxyl group, TBC appeared to be slightly more efficient in dissociating the asphaltenes, which explained its higher effectiveness in restoring the rheological properties as compared to DBP. Both the rheology and simulation results suggested that the plasticizers were rejuvenating instead of simply softening the aged asphalt.