Study on the Effects and Mechanisms of Different <scp>RPE</scp> / <scp>RPP</scp> Ratios on the Properties of Modified Asphalt

ABSTRACT Recycled polyethylene (RPE) and recycled polypropylene (RPP) are the most abundant types of plastic waste. Developing novel base asphalt modifiers (additives used to enhance the properties of asphalt) by blending RPE and RPP in different ratios is of significant importance, as the composition directly influences both the properties of BM (blend modifiers of RPE/RPP) and the performance of BM‐modified asphalt (the asphalt obtained by adding modifiers (such as rubber, resin, and polymer) to improve its performance). This study investigated the performance of BM and BM‐modified asphalt prepared with different RPE/RPP ratios, as well as the underlying mechanisms. The results show that the notch impact strength and elongation at break of BM increase with a decrease in the RPE/RPP ratio, with a turning point observed at a 6:4 ratio. However, the influence of the ratio on tensile strength and flexural strength is relatively small. The findings are supported by infrared spectroscopy analysis. For BM‐modified asphalt, the penetration at 25°C, ductility at 25°C, and viscosity exhibit an increasing trend from an RPE/RPP ratio of 10:0 to 6:4, followed by a decrease as the ratio shifts from 6:4 to 0:10. Conversely, the softening point follows the opposite trend. Infrared spectroscopy analysis of the BM‐modified asphalt indicates that the ester group index reaches its maximum value of 0.812 at the 6:4 RPE/RPP ratio, suggesting that the interaction between RPE and RPP in BM significantly influences the properties of the modified asphalt. The physical blending between pure BM and the matrix asphalt has also been confirmed. Microstructural analysis of BM and BM‐modified asphalt demonstrates that when RPE/RPP = 6:4, the compatibility between BM and matrix asphalt is optimal. The conventional property changes of the BM‐modified asphalt are also validated, reinforcing the effectiveness of RPE and RPP. These findings suggest that selecting the optimal RPE/RPP ratio can significantly enhance the mechanical and rheological properties of BM‐modified asphalt, offering a promising approach for improving asphalt performance through recycled plastic waste utilization.