Low-temperature rheological behavior of ultraviolet irradiation aged matrix asphalt and rubber asphalt binders

In order to investigate the influence of ultraviolet (UV) irradiation aging on the rheological properties of asphalt binders at low temperatures, this paper analyzes the low-temperature rheology characteristics (stiffness modulus S and tangent slope m) of matrix asphalt and rubber asphalt in the bending beam rheometer (BBR) test. The beam of asphalt binder was shaped in an advanced mold to receive more ultraviolet irradiation. The asphalt samples were subjected to different given UV-irradiation time (50 h, 100 h, 200 h, and 300 h) after thin film oven test (TFOT), with an indoor UV-irradiation aging simulation system. As comparative groups, corresponding original samples and thermal-oxidative aged samples from TFOT and pressurized aging vessel (PAV) test were also measured in BBR. Furthermore, based on the viscoelasticity theory, Burgers model was utilized to describe the constitutive relationship. In order to achieve a global solution, genetic algorithm (GA) was adopted for the nonlinear regression of viscoelasticity parameters (Ee, Ed, η1, and η2) under different aging conditions. The results show that TFOT-UV aging had a different influence on the matrix asphalt and rubber asphalt. The effect of TFOT-PAV aging to the (relative variation ratio of) viscoelastic parameters was equivalent to that of TFOT-UV aging during the irradiation time less than 100 h to the rubber asphalt. Along with the UV-irradiation time increasing, the S increased and m decreased, therefore, the low-temperature performance of asphalt binders became worse.