Quantifying Particle and Interaction Effects of Crumb Rubber on Asphalt Rheology at High Temperatures

To evaluate the respective contributions of the crumb rubber (CR) particle effect (PE) and the CR-asphalt interaction effect (IE) to the high-temperature rheological performance of crumb rubber modified asphalt (CRMA), a CR filtration approach was designed to physically separate CR particles from CRMA. Fluorescence microscopy (FM), dynamic shear rheometer (DSR) tests, and gray relational analysis (GRA) were conducted on CRMA binders with different CR particle sizes and contents before and after filtration. The results indicate that the retained CR ratio (Rcr) increased with the increasing CR particle size and content, and coarser CR and higher CR contents generally increased G* and decreased δ, indicating enhanced high-temperature deformation resistance and recoverable deformation capacity of CRMA. After filtration, G* decreased markedly, whereas δ increased, and the quantified PE and IE results further indicate that the enhanced high-temperature rheological performance is dominated by PE, with IE providing an additional contribution, particularly at higher CR contents. Moreover, Rcr correlated positively with G* and negatively with δ, and GRA suggested that CR content acts as the primary factor affecting high-temperature performance, while CR particle size serves as a secondary factor. Overall, this study provides practical guidance for optimizing CRMA design and supports improved asphalt service performance.