Effect of microwave and deodorant treatments on long-term aging characteristics of crumb rubber modified asphalt

This research examined and compared the effect of microwave and deodorant treatments on the rheological and microscopic characteristics of crumb rubber modified asphalt (CRMA) after long-term aging. Although the emissions from the asphalt modified by microwave treatment of crumb rubber (CR-micr) or high-alkane alcohol deodorant treatment of crumb rubber (CR-de) are reduced significantly compared with the ordinary CRMA, the research on their rheological and microscopic properties after aging is insufficient (especially for the CRMA with CR-de), which may pose a potential risk to their application in road engineering. To address this issue, this paper first used the rolling thin film oven and pressure aging vessel test to imitate the long-term aging of CRMAs. Then, the rheological properties of aged CRMA samples were evaluated using a dynamic shear rheometer and a bending beam rheometer. Meanwhile, the surface micromorphology, micromechanical characteristics and the chemical functional groups of CRMA samples before and after long-term aging were characterized by atomic force microscopy (AFM) and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that the microwave treatment can enhance the fatigue life of the long-term aged CRMA by approximately 29 % under 8 % CR content and 3 % strain level, while effectively improve the resistance to low-temperature cracking. Meanwhile, after long-term aging, the carbonyl index of CRMA with CR-micr is 36 % lower than that of CRMA with CR-de and 50 % lower than that of ordinary CRMA. The micromechanical modulus of CRMA with CR-micr is also lower than that of CRMA with CR-de and ordinary CRMA. These findings manifest that the microwave treatment can improve the ability of CRMA to resist long-term aging, and the deodorant treatment does not have an adverse effect on this ability.