Investigating the effects of antioxidants on the aging characteristics of crumb rubber modified asphalt

Abstract

Crumb rubber modified asphalt (CRMA) has gained significant interest due to its eco-friendly properties. However, there is still a limited understanding of its anti-aging properties, particularly with regards to the impact of antioxidants on its physical and chemical structure. This study aims to investigate the effect of three antioxidants (Irgafos 168, Irganox 1098, and Irganox 1076) on the chemical and physical properties of CRMA binders during short-term and long-term aging. The physical, rheological, and chemical properties of different samples were analyzed before and after aging using conventional physical and rheological tests, as well as Fourier transform infrared spectroscopy (FTIR). The results showed that the plastic deformation behavior of CRMA at low temperature was enhanced by modification with antioxidants, with Irgafos 168 exhibiting the most pronounced effect. After aging, CMRA showed a decline in both physical and rheological properties. In contrast to the control sample (CMRA), the three types of antioxidants displayed superior ability to alleviate the decrease in asphalt properties during short-term aging. Nevertheless, their effectiveness decreased significantly during long-term aging, possibly due to antioxidant degradation. The FTIR results revealed that the inclusion of antioxidants can effectively retard the increase of carbonyl index, with Irganox 1098 displaying the most notable impact. Nonetheless, the presence of sulfides in rubber powder limits the utility of sulfoxide index as an indicator for the degree of CRMA aging.