Improving recycled asphalt using sustainable hybrid rejuvenators with enhanced intercalation into oxidized asphaltenes nanoaggregates

This paper introduces a new bio-rejuvenator made from a blend of high-protein algae and high-lipid animal manure and studies its interaction with aged bitumen molecules to revitalize aged asphalt. True revitalization requires restoring not only the chemical balance but also the molecular conformation. Therefore, rejuvenators should be able to de-agglomerate oxidized asphaltenes while compensating for components that are lost during aging. This study uses a balanced feedstock to control the composition and concentration of active molecules in a rejuvenator to increase its efficiency. To do so, a balanced combination of high-protein algae and high-lipid manure were used to synthesize bio-rejuvenator having different concentration of straight chain hydrocarbons and aromatic compounds, with the former helping to restore chemical balance, and the latter working to de-agglomerate oxidized asphaltene. This in turn can restore aged bitumen's molecular conformation, leading to restoration of its physicochemical and rheological properties. The study results showed that bio-rejuvenator produced from the algae-manure balanced feedstock was more effective rejuvenator than using either of algae or manure solely. The superiority of rejuvenator made by co-liquefaction of a balanced feedstock verified by comparing its dosage efficiency with that of its counterparts made from isolated bio-mass sources. The comparison was done based on the extent of increase in crossover modulus and crossover frequency of an aged bitumen doped with a constant dosage of each rejuvenator with co-liquified scenario showing a much higher increase than other scenarios. Molecular dynamics simulation results revealed that latter bio-rejuvenator's molecules have a peptizing effect on oxidized asphaltene molecules leading to a significant decrease in the radial distribution function of oxidized asphaltene molecules restoring their molecular conformation. This in turn leads to revitalizing aged asphalt physio-chemical properties to enable reuse and recycling of aged asphalt composites and improve recycling of asphalt pavements to promote sustainability.