Investigation of the influence of the variable-intensity ultraviolet aging on asphalt properties

Abstract

Currently, researches related to asphalt UV aging mostly based on constant-intensity UV radiation, which is not consistent with its real service condition. In this study, the variable-intensity and constant-intensity UV radiation conditions were proposed on the principle of constant total radiation. The UV-aged neat asphalt film thickness was 1 mm and 0.5 mm. The temperature sweep, frequency sweep, and multiple stress creep recovery tests were conducted to reveal the rheological properties of UV-aged neat asphalt. Moreover, the Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) tests were performed to reveal the microscopic properties of UV-aged asphalt. Regarding the constant-intensity UV-aged asphalt with 1 mm film thickness, the rutting parameter aging index (RPAI) of 9 cycles was smaller than that of RTFO-aged asphalt. The variable-intensity UV aging induced a much larger aging effect than constant-intensity UV aging for UV-aged asphalt. The ISO and ICO under variable-intensity UV aging conditions is higher than constant-intensity UV aging for the same cycles. Besides, the asphalt thickness is an essential element affecting UV aging. The aging effect increased significantly as the film thickness decreased. SEM test results have indicated that the variable-intensity UV aging caused more microscopic morphology damage to asphalt than constant-intensity UV aging. Variable-intensity UV aging test condition proposed in this study is more accurately simulate the real service conditions. It is meaningful to propose the variable-intensity UV aging process. This study provides new ideas for simulating UV aging conditions and methods in the laboratory.