Uniformity and mechanical performance of recycled asphalt mixtures with high RAP content based on refined decomposition: a comparative study with conventional separation

In view of the challenges of limited natural resources and environmental pollution, recycled asphalt pavement (RAP) is increasingly utilized in asphalt mixtures. To enhance the utilization efficiency of RAP, it is essential to separate the aged asphalt from the aggregates within RAP. Currently, commonly used physical separation technologies include conventional separation as well as refined decomposition. The objective of this study is to compare the uniformity and mechanical performance of recycled asphalt mixtures (RAM) with high RAP content based on the 2 separation technologies. Firstly, RAP materials were pre-processed by these two technologies (named as RAP-CS and RAP-RD respectively), followed by the preparation of RAM with varying RAP contents. Subsequently, the uniformity of the RAM was evaluated by analyzing deviations in gradation and the asphalt-aggregate ratio. Furthermore, digital image processing (DIP) technology was employed to analyze the cross-sectional images of the compacted specimens of RAM. Finally, the mechanical performance of RAM were evaluated through dynamic modulus tests, dynamic creep loading tests and low-temperature semi-circular bending (SCB) tests. The correlation between the uniformity and mechanical performance of the RAM was analyzed. Results indicate that compared to RAP-CS, RAP-RD show superior uniformity in gradation and asphalt-aggregate ratio. Moreover, RAM prepared with RAP-RD shows superior aggregate dispersion uniformity and enhanced mechanical performance. Pearson correlation analysis revealed that better dispersion uniformity corresponded to lower dynamic modulus at low frequencies and higher values at high frequencies, greater axial strain and axial strain rate at elevated temperatures, and enhanced the low-temperature SCB strength.