Optimization of the Preparation Process and Performance Evolution of High-content Crumb Rubber Modified Asphalt

Abstract: Despite the extensive application of waste tires in asphalt modification, there is a distinct lack of systematic research regarding high-content (>20%) crumb rubber and its coupled modification mechanisms. Consequently, this study employed 70# base asphalt and 15%–27% recycled crumb rubber (20–100 mesh) to evaluate their interaction and performance evolution. Correlation mechanisms between process parameters and performance were revealed through macroscopic performance tests (e.g., penetration, softening point, ductility) and microscopic characterizations (e.g., SEM, EDS, FTIR). The results indicated that as the modification temperature increased, the penetration increased linearly from 4.2 ± 0.33 mm to 6.2 ± 0.25 mm, the softening point remained stable initially and then decreased (with a peak value of 65.8 ± 4°C), and the ductility increased continuously from 5.1 ± 0.61 cm to 8.96 ±0.64 cm. The optimal process parameters were determined as follows: temperature of 210-220°C, time of 90 min, dosage of 21%, and mesh size of 60 mesh. Under these conditions, Marshall stability reached 8.6 kN, and dynamic stability was 5382 ± 106.4 cycles/mm, exhibiting both excellent mechanical properties and environmental adaptability. Microscopic analysis showed that a uniformly dispersed system was formed by physical blending of crumb rubber with base asphalt. A desulfurization effect was observed under high- -speed shearing (with sulfur content reduced by 12%-15%). FTIR confirmed the absence of new functional groups, indicating that the modification was primarily physical cross-linking. This study provided process parameters and Theoretical foundation for the engineering application of asphalt modified with high-content recycled crumb rubber, promoting the high-value utilization of waste tires in green pavement materials and reducing carbon emissions.