In the rapid development of sponge city construction in China, porous asphalt pavement has been widely used. The high-viscosity modified asphalt used for porous asphalt pavements is utilised in a complex aging environment. In this study, infrared spectroscopy was used to test the changes in the functional groups of high-viscosity modified asphalt under the influence of ultraviolet radiation intensity, high temperature, and water corrosion conditions. The research results showed that under the influence of several environmental factors, the high-viscosity modified asphalt has no chemical reaction but does undergo physical changes. From the perspective of the functional group index, the carbonyl index is more suitable for evaluating the degree of ultraviolet aging, and the sulfoxide group index is more suitable for evaluating the effect of temperature on aging. The high-viscosity modified asphalt aging kinetic models, established with different functional group indexes as indicators, have different activation energies. The aging kinetic model established with the carbonyl index is more suitable for simulating traditional thermal-oxidative aging. This study provides a better plan to reveal the influence of different environmental factors on the aging performance of high-viscosity modified asphalt under complex environmental conditions.

It is significant to capture the microstructure characteristics and evolution of asphalt mixtures since it is well related to the macroscopic pavement performance. The X-ray Computed Tomography (CT) technique is a suitable candidate to gather and analyse the image information of the internal structure for materials. An advanced repeated load permanent deformation (ARLPD) test that could largely simulate the confining pressure and temperature gradient of actual pavements was conducted on several typical newly constructed and overlay pavement structures. CT and digital image processing techniques were used to characterise the evolution behaviour of microstructure and damage in asphalt layers before and after testing at high temperatures. Combining the macroscopic pavement performance with microstructure evolution, the failure mechanism for different pavements and layers was finally discussed. It is found from the ARLPD test that newly constructed hot mix asphalt pavements show much better rutting resistance than the overlay pavements. The middle asphalt layer and the overlay layer, respectively, contribute approximate half of the total rut depth for newly constructed and overlay pavements. After testing, the change of air void content varies in different layers and pavements, indicating different rutting mechanisms (densification or shear flow). In the middle asphalt layer of overlay pavements, some cracks are formed with a great increase in air void aspect ratio and a significant decrease in air void number. Using the crack density as an indicator, the correlation of permanent deformation and cracks at high temperatures is preliminarily found.