Investigating bio-rejuvenation mechanisms in asphalt binder via laboratory experiments and molecular dynamics simulation
M Zadshir and DJ Oldham and S Hosseinnezhad and EH Fini, CONSTRUCTION AND BUILDING MATERIALS, 190, 392-402 (2018).
Oxidative aging can have a detrimental impact on the asphalt binder's thermo-mechanical properties and consequently the performance of the pavement. This paper investigates effects of three modifiers (one petroleum-based and two bio-based) on thermo-mechanical properties of an oxidized asphalt binder. Rheological tests and chemical characterization analyses were performed to examine whether oxidized asphalt binder properties could be restored. Accordingly, physiochemical and rheological characteristics of oxidized and rejuvenated asphalt binder were examined via a combined experimental and modeling approach. The effect of rejuvenators was evidenced by the rejuvenators' ability to successfully reduce large molecular size ratio of asphalt that was increased due to oxidation. Moreover, colloidal stability evaluation showed that rejuvenators were effective in improving the stability of the asphalt matrix, which was disturbed due to oxidation. Study of intermolecular interactions using molecular dynamics simulation further showed that amide groups in bio-rejuvenators interact with asphaltene molecules increasing the stacking distance of asphaltene dimers while changing their conformational packing. This, in turn, may explain some of the observed improvements in rheological properties. Experimental results showed that the rejuvenators were effective in restoring oxidized asphalt's thermo-mechanical properties as reflected in the reduction of viscosity and stiffness as well as an increase of stress relaxation capacity and fracture energy. (C) 2018 Elsevier Ltd. All rights reserved.
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