Optimization of composite-modified asphalt ratio and performance evaluation of rich bottom layer mixes

This study focused on developing a high-toughness composite-modified asphalt (CMA), to enhance the performance of rich bottom layer mixes and its crack resistance. The content of crumb rubber (CR), epoxy resin (ER), and polyaryl polymethylene isocyanate (PMDI) were chosen as design parameters. Response surface methodology (RSM) was employed to develop models for creep strength (S), fatigue performance parameter (N_f), yield energy (YE), and Brookfield viscosity (BV) of CMA. Then, these models were used to optimize the content of modifiers. Additionally, rich bottom layer mixes were designed using SBS-modified asphalt (SMA) and the newly developed CMA as binders, and their performances were evaluated. The results demonstrated the accuracy and predictive ability of the RSM models. The composite-modified asphalt mixes (CMAM) showed superior road performance and crack resistance compared to SBS-modified asphalt mixes (SMAM). Importantly, CMAM aligned effectively with the functional requirements of the rich bottom layer. This research contributes novel materials and methods for enhancing pavement crack resistance, providing valuable insights for improving the durability and longevity of pavements.