Mechanical and internal structural damage evolution in cold recycled mixture under fatigue loading

Cold recycling technology has the virtue of lower cost, fewer pollutant emissions, and less consumption of raw materials and fossil fuels in pavement maintenance and construction. This study aimed to investigate the evolution of fatigue damage in cold recycled mixtures and provide a theoretical basis for improving the service life of cold recycled pavements with high reclaimed asphalt pavement (RAP) utilization rates, ultimately contributing to energy and resource conservation. To achieve this objective, we conducted a study on the mechanical and internal structural damage evolution of cold recycled mixtures produced using different agents (cement and asphalt emulsion). This was accomplished by combining indirect tensile fatigue testing with X-ray CT scanning techniques. The results indicate that the mechanical response of cold recycled mixtures under fatigue loading is closely related to the evolution of their internal structure during various stages of fatigue. Furthermore, it is found that the type of stabilization agent used in these mixtures has a significant impact on their initial air void content and volume distribution, which ultimately affects both the rate and extent of their mechanical and structural damage evolution. Based on these results, recommendations have been proposed for enhancing the fatigue performance of cold recycled pavement through appropriate mixture design strategies that account for these factors mentioned above.