Molecular simulation and experimental analysis of interaction and compatibility between bitumen and grafting-activated crumb rubber

The pretreatment of crumb rubber (CR) through activation demonstrates potential improvements in compatibility with base bitumen. However, existing studies have mainly focused on macroscopic performance characterization, with insufficient research on microscopic mechanisms. This paper employed molecular dynamics (MD) simulation to explore the compatibility between grafting-activated crumb rubber (GACR) and bitumen. A quantitative analysis of crumb rubber and bitumen compatibility was conducted using indices such as electric dipole moment, solubility parameter, interaction energy, radial distribution function, and electron density. The outcomes of the MD simulation were further validated through segregation and dynamic shear rheology experiments. The results indicated that GACR had a higher polarity, smaller solubility parameter difference, and greater interaction energy with base bitumen than CR. At 160°C, the solubility parameter difference between GACR and bitumen is merely 0.02(J/cm 3 ) 1/2 , and the interaction energy with the asphaltene was enhanced by 31.12 %. Notably, GACR demonstrated a more positive impact on the compactness of base bitumen than CR, indicating superior compatibility. The adsorption mechanism of GACR on bitumen was explored by calculating the electron density, and the enhanced electrostatic interaction between GACR and bitumen explained the compatibility mechanism between the activated crumb rubber and bitumen. The softening point differences and rutting factor segregation indices also confirmed that bitumen modified with GACR had better storage stability. The simulation results strongly correlated with experimental outcomes, providing a valuable reference for proposing effective methods to enhance compatibility between CR and bitumen.