Experimental Studies on UV Aging of Asphalt Using Rheological and Image Analysis
摘要
An inherent characteristic of asphalt is aging. Apart from thermo-oxidative aging, photo-oxidative aging predominantly causes the aging of asphalt in Asian countries due to its higher exposure to UV radiations, which constitute 3–5% of the solar spectrum. To investigate the UV aging in different binders in India, which included VG40 and PMB 70-XX binders were exposed to UV aging in the laboratory and natural exposure conditions after short-term aging. In the laboratory, 1000 μm thin asphalt film was aged, while for natural exposure conditions, 100, 500, and 1000 μm thickness were considered. 1000 μm thick specimen in the laboratory was aged at 70 °C for a duration of 7 days at a UV intensity and wavelength of 63.66 W/m2 and 365 nm, respectively. During lab aging, the wind speed was maintained at 15 kmph. For natural exposure conditions, the binders were aged for 1, 3, and 6 months duration. The appearance of the binder surface after UV aging depicted a loss of luster in the lab while depicting significant cracking in the natural exposure condition. The cracked area was quantified using image analysis, which indicated a steep increase as the binder film became thinner. The rutting parameter of UV-aged binders in the lab almost increased by 100% compared to STA-aged binders after 7 days of UV aging. Further, %recovery reduced with UV aging indicating damage to the polymer chains in PMB. Overall, the study recommends that UV aging plays a major role in constructing climate-resilient pavements and should be considered in selecting appropriate asphalt types.