This paper uses a multiscale approach to study the preferential surface adsorption of bio-based rejuvenators to siliceous substrates, used here as surrogates for mineral stones like quartz in bituminous composites. Bituminous composites are the main building blocks of asphalt pavements and roofing shingles. Various rejuvenators, including bio-based rejuvenators, are commonly used to extend the service life or facilitate the recycling of aged bituminous composites reclaimed at the end of their service life. While rejuvenators may be able to restore the thermomechanical properties of aged asphalt, the rejuvenators' susceptibility to moisture damage is a rising concern as various types and dosages of biorejuvenators gain traction in the market. Here, we hypothesize that by controlling the composition of rejuvenators, the adsorption of rejuvenators to siliceous minerals in a wet environment can be increased, leading to enhanced resistance to moisture damage in revitalized aged asphalt. To test this hypothesis, we specifically designed a rejuvenator from a balanced feedstock of algae (high in protein and nucleic acids) and manure (high in lipid), and we compare its resistance to moisture damage with that of two commercial rejuvenators, using molecular modeling and laboratory experiments. Molecular modeling was geared toward simulation, and laboratory experiments were performed using the moisture-induced shear-thinning index (MISTI) and the wheel-tracking test under water. The study results showed that even though the aged asphalt was not susceptible to moisture damage, its moisture susceptibility varied significantly after it was revitalized by each of the three rejuvenators tested. Our molecular simulations showed that water promoted the desorption of molecules of low-performing rejuvenators from the siliceous stone surface, giving rise to moisture damage. This finding was supported by laboratory experiments showing a water-stripping inflection point (SIP) and a significant change in the shear-thinning slope after water exposure. The hybrid rejuvenator did not show any evidence of desorption or a stripping inflection point; this can be attributed to the presence of amide-enriched compounds in the hybrid rejuvenator that resulted from feedstock with a balanced combination of protein, nucleic acids, and lipids. The results of this study highlight the importance of accounting for a rejuvenator's composition to ensure that the rejuvenator's introduction to aged bitumen does not negatively impact the durability of the bituminous composite. This is even more critical for severely aged asphalts, which may require a higher concentration of rejuvenators to restore their properties. The study outcome provides insights to formulators and manufacturers to account for durability in their attempts at recycling and resource conservation to enhance sustainability in construction.
ASJC Scopus subject areas
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering