Investigation of the rheological modification mechanism of crumb rubber modified asphalt (CRMA) containing TOR additive

Crumb rubber obtained from scrap tires has been incorporated with asphalt binder to improve the performance of asphalt mixtures in the past decades. However, rubber asphalt mixtures demand higher production temperatures than conventional asphalt binders due to the higher viscosity of asphalt rubber binder. The objective of this paper is to evaluate the rheological properties of crumb rubber modified asphalt by adding trans-polyoctenamer rubber (TOR) additives and investigate the modification mechanism between TOR and crumb rubber modified asphalt. In this study, CRMA was prepared by mixing Karamay 70 penetration grade base asphalt at 15%, 20% and 25% crumb rubber proportions by weight of asphalt. TOR, a typical reactive modifier, was added to CRMA at two percentages of 0% and 4.5%, respectively. Several conventional laboratory rheological tests were carried out to evaluate the performance of CRMA with and without TOR additive at different temperatures. Furthermore, in order to investigate the interaction mechanism of TOR and CRMA, a series of advanced tools, including the scanning electron microscopy (SEM) test, differential scanning calorimeter (DSC) test, Fourier transform infrared spectroscopy (FTIR) test were conducted. From the experimental results obtained, it may be concluded that CRMA with adding TOR not only improves the engineering properties of the rubber modified asphalt, but also improves the performance of asphalt rubber. From the microscopic tests, it is concluded that there is a complex chemical reaction between TOR and CRMA, which changes the rheological properties of CRAM and contributes to the storage stability of asphalt binder.