Aging effects of ultraviolet lights with same dominant wavelength and different wavelength ranges on a hydrocarbon-based polymer (asphalt)

To investigate the effects of different wavelength ranges of UV lights on chemical compositions and macro-properties of asphalt, three UV lights were used to conduct the aging test of asphalt for 1-288 h. The elemental analysis and Fourier transform infrared spectroscopy (FTIR) were performed to analyze the chemical changes of asphalt, the surface micro-topographies of asphalt before and after UV aging were studied by atomic force microscopy (AFM). In addition, the physical performance, viscosity and rheological performance of asphalt was studied with softening point test and dynamic shear rheometer (DSR), respectively. The chemical compositions and structures analyses show that the oxidation mechanism exists during the UV aging of asphalt binder. The numbers of bee-like structures in AFM height figures decrease obviously after UV aging, meanwhile the sizes of which increase. The relationships of RCC, RCS and SPI values with UV expose time follow a power function model in the first 24 h, while follows a liner model after 24 h. UV lights with different wavelength ranges have significantly different effects on the chemical compositions and macro-properties of asphalt. The UV 350-370 nm has the most obvious aging effect on asphalt binder, second is the UV 340-380 nm, the UV 200-400 nm has the lightest aging effect.