Investigating Aging and Rejuvenation Mechanism of Biomodified Rubberized Bitumen

Abstract

This study examines the effects of five biomodifiers on the aging and rejuvenation of biomodified rubberized bitumen. It further discusses the challenges associated with restoration and reuse of aged bitumen, especially bitumen located in a geographic area with high ultraviolet intensity. Exposing bitumen to oxidation changes its colloidal stability, whereas the content of asphaltene increases, and the content of aromatics decreases as aging progresses. In addition, bitumen’s evolution during aging includes oxidation, aromatization, chain scission, and carbonization, which alters bitumen’s molecular structure and subsequently its restoration capacity. To revitalize aged bitumen, a need exists to restore bitumen’s molecular conformation. The latter becomes more complex when rubber molecules are involved because the presence of polymeric structures and carbon black in tires could have counteracting effects on bitumen’s aging. The polymer structure can degrade and act as a sacrificing agent, whereas carbon black might work as an ultraviolet blocker and free radical scavenger. In addition, the presence of other modifiers, such as bio-oils, could alter the evolution of aging. To study the interplay of modifiers on the aging evolution of rubberized bitumen, this study compares the resistance to the ultraviolet aging of various biomodified rubberized bitumens. It further examines the efficacy of a rejuvenator to restore each aged bitumen. This study found that not all biomodified rubberized bitumens had similar restoration capacity. The results indicated that bitumen containing a wood-based modifier has the least signs of aging among all scenarios studied. This finding can be attributed to the presence of a significant content of furfural in the wood-based modifier that helped reduce molecular-level changes. After aging, each specimen was rejuvenated using a biobased rejuvenator. The success of rejuvenation was tracked using the rejuvenating index calculated based on the extent of the changes in the chemical and rheological properties of rejuvenated bitumen. Aged wood-based rubber modifier was found to need the lowest dosage (5.7%) of the rejuvenator to be restored, followed by corn stover (8.3%), miscanthus (8.4%), waste vegetable oil (9.81%), and castor oil-based rubber modifier (10.87%). The study results indicate that the composition of biomodified rubberized bitumen not only affects its evolution during aging but also its rejuvenation capacity.