## 1 Introduction  
Asphalt pavement has been widely used in the road field because of its good elasticity and plasticity, high driving comfort and strong load capacity [1, 2]. At present, asphalt pavement is made of hot mix asphalt (HMA). However, HMA needs to heat the asphalt to more than 160 \({}^{\circ}\)C, and the temperature of the paving and compaction of the mixture is usually not lower than 140 \({}^{\circ}\)C [3]. Heating asphalt and mineral materials consumes a large amount of energy. Large amounts of smoke and toxic gases are emitted during construction, which have many adverse effects on the construction workers and the environment. While global warming and energy shortages are receiving increasing attention, researchers and users in the asphalt industry are working hard to find some environmentally-friendlymaterials and technologies. Warm mix asphalt (WMA) is a mixture that can be mixed and compacted at relatively low temperatures using some WMA techniques [4]. WMA yields numerous mechanical, environmental, economic, and operational benefits through lowering its production temperature by 10 \({}^{\circ}\)C to 38 \({}^{\circ}\)C compared to conventional HMA [5]. As a green road construction technology with energy saving and emission reduction, WMA has attracted widespread attention. At the same time, its technical characteristics of reducing mixing and compaction temperature of asphalt mixture make its moisture damage more complex than that of HMA. Because of these numerous potential benefits, the use of WMA has increased rapidly over the past decade [6; 7]. WMA may cause moisture damage because of the lower production temperature. Many studies have been performed on the moisture damage of WMA mixtures [8]. It was observed that WMA was more water sensitive than HMA [9; 10]. Evotherm WMA and foamed bitumen WMA have better water stability than the other WMA [11; 12]. The water stability of Sasobit WMA is significantly lower than that of HMA. As a result, the adhesion capacity of the interface between WMA and aggregate is low, and water damage is more likely to occur than in HMA [13; 14]. Most of the research was carried out in the laboratory without considering the changes of moisture susceptibility of WMA under the usual conditions. During the construction process and long-term use, the asphalt material is inevitably affected by environmental factors such as light, heat, and water, which cause the asphalt binder and the mixture to age, to a certain extent, thus affecting moisture damage. Research on the heat aging of asphalt has been carried out, and uniform test standards and specifications have been established. However, research on photo-oxidation aging of asphalt is relatively rare, and there is no uniform test standard. Furthermore, the aging effect of light cannot be ignored [15; 16]. Although ultraviolet light accounts for only 5% in the solar spectrum, its shortest wavelength and highest energy can destroy the molecular structure of the material, resulting in performance degradation of the asphalt binder [17; 18]. Ultraviolet (UV) aging mainly occurs on the surface of asphalt. Photo-oxidation aging has a significant effect on the performance of asphalt at a depth of 3 \(\upmu\)m, which gradually decreases with the increase of asphalt film thickness [19]. Macroscopically, the degree of penetration, ductility decrease, viscosity, and softening point increase. Microscopically, resulting in an increase in colloidal instability index and relative carbonyl index, large-molecular-weight substances are formed, and asphalt performance deteriorates [20; 21]. The performances of UV aging and pressure aging vessel (PAV) aging on asphalt by means of penetration, ductility, softening point, and viscosity were compared. It was found that UV 100 h \(<\) PAV \(<\) UV 200 h [22; 23].