AbstractUltraviolet (UV) radiation and thermal oxidation are two leading causes of the aging of asphalt pavements. However, there is a lack of a suitable analytical model to consider both when the field aging gradient of asphalt pavement is analyzed. This work develops a framework of using coupled diffusion-kinetics aging model (CDKAM) to quantify the field aging gradient in asphalt pavements, which considers the influence of both UV and thermal conditions. First, the general diffusion model based on Fick’s second law is proposed to analyze asphalt aging extent and aging gradient due to UV radiation. Then, the kinetics model that could quantify the thermal aging of asphalt is revised and coupled with the diffusion model to develop the CDKAM. Both the diffusion model and CDKAM are validated using the experimental data from the literature. The results exhibit the efficacy of using the diffusion model to analyze the asphalt aging gradient under UV radiation. The CDKAM is demonstrated to be an effective model in assessing the field aging gradient in asphalt pavements. The required inputs for CDKAM are discussed, and future works are recommended to improve the accuracy of using the CDKAM to predict the field aging in asphalt pavements.

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