Selective adsorption of bio-oils’ molecules onto rubber surface and its effects on stability of rubberized asphalt

This study examines the merits of surface activation of rubber using various bio-oils to improve rubber-asphalt interaction. To do so a hybrid method combining microwave irradiation and bio-chemical treatment was used to graft biomolecules onto the exterior surface of the rubber. Five surface activated rubbers were prepared using waste vegetable oil, wood pellet, miscanthus, corn stover, and castor oil. The effectiveness of each oil was examined by measuring the chemisorption of the bio-oil and elastic recovery of bitumen containing rubber particles treated with each bio-oil. Our quantum-based density functional theory calculations showed presence of both physical and chemical interactions between polar aromatic components of bio-oils and rubber. Among studied bio-oils, wood-based bio-oil found to have the highest content of polar aromatics such as phenolic resins leading to its enhanced interaction with rubber. This was evidenced in percent recovery, which was nearly doubled (from 13% to 24%) when wood-based bio-oil molecules were grafted onto the surface of rubber. Overall, wood-based bio-oil was shown to adsorb well to the rubber surface and reduce its tendency to separate from bitumen by 82%. The study results showed how composition of bio-oil affects its efficacy to activate rubber surface. It also proved the technical merits of using surface activated rubber to reduce segregation between rubber and bitumen which commonly occurs in rubberized asphalt. Therefore, the outcome of this study promotes recycling of waste tire to promote sustainability in pavement construction.