Chemo-rheological, mechanical, morphology evolution and environmental impact of aged asphalt binder coupling thermal oxidation, ultraviolet radiation and water

Thermal oxidation, ultraviolet radiation and water significantly affect the aging of asphalt pavement, and the aging causes more serious emissions into aqueous environment. This study designed four aging methods to conduct coupling aging tests, and the dynamic shear oscillatory test, FT-IR spectrometer, gel permeation chro-matography (GPC), binder bond strength test (BBS), fluorescent microscope, scanning electron microscope, and surface free energy (SFE), and zebrafish aquatic toxicity tests were used to explore the rheological, chemical, adhesive, surface evolution, and the environmental impact of asphalt binder. The aging degree increased under four aging methods, which led to a higher modulus, a lower phase angle, more oxygenated chemicals and asphaltenes, and higher water sensitivity. Thermal oxidation and ultraviolet radiation had the most significant aging acceleration effect. Although water greatly weakened the aging acceleration effect of UV radiation, through physical diffusion and chemical hydrolysis, water led to crack propagation, rougher surface and even holes coupling with high temperature, which increased the damage to the asphalt binder and the BBS failure mode changed from cohesion failure to adhesion failure. The results of the environmental impact of the organic matter released from the aged asphalt indicated that the asphalt leaching solution had certain biotoxicity. Moreover, the aged asphalt leaching solution was diluted 10 and 100 times, and the biotoxicity decreased significantly with the decrease of the concentration.

Automated summary

Thermal oxidation, ultraviolet radiation, and water all have significant impacts on asphalt pavement aging, which in turn leads to more serious emissions into aqueous environments. This study used four aging methods to conduct comprehensive aging tests on asphalt binders, evaluating their rheological, chemical, adhesive, surface evolution properties, as well as their environmental impact. The results showed that the aging degree increased under all four aging methods, resulting in increased modulus, decreased phase angle, higher presence of oxygenated chemicals and asphaltenes, and increased water sensitivity. Thermal oxidation and ultraviolet radiation had the most significant acceleration effect on aging. Water, while weakening the aging acceleration effect of UV radiation, led to crack propagation, rougher surface, and increased damage to the asphalt binder. Additionally, the biotoxicity of the leaching solution from aged asphalt was found to decrease significantly with decreasing concentration.