Laboratory Evaluation of Cold Patching Asphalt Mixture with Refined–Processed Recycled Asphalt Pavement

This study investigates the effects of two separation processes: traditional separation technology (TST) and refined separation technology (RST), on the characteristics of recycled asphalt pavement (RAP) and the performance of cold patching asphalt mixtures (CPAM). The research evaluates the RAP separation efficiency, focusing on asphalt content and agglomeration degree, and examines the mechanical, high- and low-temperature, moisture susceptibility, anti-stripping, and fatigue performance of CPAM with varying RAP content (0–75%). A key innovation of this study is the exploration of using RST-RAP for CPAM production in comparison to TST-RAP. The findings reveal that the RST process significantly enhances the separation of coarse aggregates from asphalt mortar, leading to improved gradation, reduced agglomeration, and better overall RAP quality compared to TST. Incorporating RAP into CPAM improved the Marshall stability, with RST-RAP showing higher performance gains than TST-RAP, particularly at higher RAP content. Additionally, the dynamic stability, low-temperature cracking resistance, moisture resistance, and fatigue life of CPAM were positively influenced by RST-RAP, with optimal performance achieved at 25–50% RAP content. In contrast, excessive RAP content, especially with TST-RAP, negatively impacted the mixture’s properties, leading to higher brittleness and reduced stability. This study highlights the novelty of using RST-RAP to enhance CPAM performance, suggesting that the RST process is more effective in improving CPAM performance. However, RAP content should be carefully controlled (25–50% for RST-RAP and ≤25% for TST-RAP) to meet technical standards and ensure optimal durability. These findings provide valuable insights for optimizing RAP utilization in sustainable pavement maintenance practices.