Deagglomeration of oxidized asphaltenes as a measure of true rejuvenation for severely aged asphalt binder

To promote sustainable engineering practices in construction, repeated use of reclaimed asphalt pavement (RAP) has been promoted. This in turn has led to the second and third generation of reclaimed materials containing severely aged asphalt binders. To facilitate recycling and reuse of these resources, there is a need to synthesize sustainable chemicals and modifiers, which can truly rejuvenate severely aged asphalt binder. This paper investigates mechanisms of true rejuvenation and introduces the ability to deagglomerate asphaltene nano-aggregates as a measure of true rejuvenation. Molecular dynamics simulations followed by rheometry and chemical characterization is used to evaluate the effect of a Bio-Rejuvenator (BR) made from bio-mass on asphalt binders aged for 60 h and 100 h in the laboratory as surrogates for highly aged asphalt binders found in the 2nd and 3rd generation of RAPs, respectively. Introduction of BR is found to be effective to disturb the nano-aggregates formed during oxidation due to the increased polarity of oxidized molecules. Some of the BR molecules are found to be more effective than others to interact with the oxidized asphaltene molecules and cause deagglomeration, whereas others play as dispersant agents to promote separation of nano-aggregates. Chemical characterization of the aged asphalt binder doped with BR shows that the colloidal stability of the systems increases and the large molecule size decreases when the BR is introduced to the aged asphalt binder. It is further observed that addition of 10% and 30% Bio-Rejuvenator to the aged asphalt binder reduces its complex modulus by 34% and 76%, respectively, bringing it closer to that of the neat binder. Overall, the study results show that the ability to de-agglomerate oxidized asphaltenes can be used as one of the measures of true rejuvenation. Such findings can help manufacturers develop effective rejuvenators to facilitate recycling and promote sustainability of construction practices. (C) 2019 Elsevier Ltd. All rights reserved.