Comparing effects of physisorption and chemisorption of bio-oil onto rubber particles in asphalt

Use of recycled rubber particles in asphalt pavements has shown to be advantageous to extend pavement service life. The challenge with the use of rubber particles which limits its wide-spread application is the segregation of rubber from asphalt matrix demanding continuous agitation; this in turn increases the cost of applying rubberized asphalt pavement. This study compares the efficacy of chemisorption and physisorption of bio-derived molecules to rubber particles and their effect on rubberized asphalt properties. The chemisorption is studied via grafting biomolecules onto the rubber surface by heat-treatment to create surface activated rubber (SAR). The physisorption is studied via bio-oil's absorption into rubber particles to produce pre-swelled crumb rubber (PsCR). The grafting process was accomplished by microwave-assisted bio-chemical treatment while the rubber particles pre-swelling was carried out by direct mixing rubber with bio-oil. Both SAR and PsCR are then added to asphalt to create rubberized asphalt for further analysis. The efficacy of each rubberized asphalt was studied via thermo-mechanical characterization. The study of storage stability showed SAR was more effective to reduce segregation index, reducing segregation of rubber and asphalt by 41%. However, the study of elastic recovery showed higher recover for PsCR. The elastic recovery of PsCR was 156 percent higher than rubberized asphalt containing non-swelled particles. PsCR also presented improved anti-cracking performance with 39% creep stiffness decrease and 17% m-value increase. The fluorescence microscopy showed that bio-oil was successfully absorbed by rubber particles significantly improving the dispersion of rubber in asphalt. Both grafting and pre-swelling of rubber particles using biomolecules improved properties of rubberized asphalt. The study results promote the use of recycled rubber to enhance the sustainability of pavement construction while promoting resource conservation and environmental protection.