Hydrogen peroxide activation of waste tire crumb rubber for improving compatibility with bitumen: Laboratory and molecular dynamics insights

Enhancing rubber-bitumen compatibility is crucial to improve pavement performance and durability. To investigate the compatibility improvement between H₂O₂-activated waste crumb rubber (AWCR) and bitumen, coarse and fine waste crumb rubber (WCR) were treated and analyzed through multi-scale characterization and molecular simulation. Microstructure and chemical changes of WCR and AWCR were analyzed with scanning electron microscope (SEM), contact angle tests and Fourier transform infrared spectroscopy (FTIR). Compatibility was also indirectly evaluated through modified boiling tests and storage stability tests. Besides, molecular dynamics was used to explore the interaction between WCR/AWCR and bitumen. SEM, contact angle, and FTIR results showed bond breakage of CC and C–C and increased polar groups like –OH and –COOH in AWCR, resulting in a rougher texture and higher surface energy. Compared with WCR, AWCR showed a lower bitumen stripping rate after boiling, and the binder with AWCR also had a lower softening point difference and segregation rate after storage. Molecular dynamics simulations further confirmed that AWCR has a closer solubility parameter and higher binding energy to bitumen than WCR, reflected in a relatively slower diffusion rate. This study provides comprehensive evidence for an eco-friendly method of WCR surface treatment for more efficient recycling of tire rubber in asphalt pavements.