Performance of asphalt anti-aging agents under coupled temperature-humidity-irradiance conditions – A case study in Ningxia, China

Asphalt pavement aging under diverse climatic stresses impairs road durability, yet climate-adaptive anti-aging strategies remain underdeveloped. Most studies focus on generic anti-aging mechanisms but overlook the impact of regional environmental heterogeneity on modifier efficacy. Particularly in regions like Ningxia with three typical microclimates, there is a lack of targeted selection systems for anti-aging agents. This study adopted seven modifiers (SiO 2 , montmorillonite, rutile/anatase TiO 2 , Mg-Al LDH, carbon black, mineral powder), which were added at a 6% dosage in #90 base asphalt. Aging tests were conducted under simulated climatic conditions of southern Ningxia (low temperature, high humidity, low irradiance), central Ningxia (moderate temperature, moderate humidity, moderate irradiance), and northern Ningxia (high temperature, low humidity, high irradiance). A climate-responsive evaluation framework for anti-aging agents was established via DSR, four-component analysis, FTIR, elemental analysis, random forest algorithm, and principal component analysis (PCA). Results showed that the efficacy of anti-aging agents was significantly climate-dependent: anatase TiO 2 (A-TiO 2 ) performed well in southern climates, the O/C ratio change rate only 1.5%, Mg-Al LDH exhibited the best performance in central climates, and carbon black (CB) was optimal in northern high-temperature and high-irradiance environments,effectively inhibiting carbonyl group formation. Random forest analysis confirmed that Resin content and saturate content were the core components regulating asphalt rheological properties. PCA reduced 8 aging evaluation indices into two principal components, enabling comprehensive quantitative assessment of anti-aging performance. Mechanism analysis revealed that LDH blocked oxygen diffusion via physical barrier effects, carbon black exerted dual functions of ultraviolet shielding and free radical scavenging, and TiO 2 stabilized asphalt components through photocatalytic activity. The region-specific anti-aging agent selection system established in this study provides a scientific basis for climate-resilient pavement design in Ningxia and similar climate-zoned regions. Future research will further explore combined climatic conditions and the road performance of anti-aging asphalt mixtures.