Study on the Properties of Waste Oil-Activated Crumb Rubber-Modified Asphalt Based on Molecular Dynamics Simulation and Rheology

To investigate the effect of activated crumb rubber content on the molecular interactions and the properties of crumb rubber-modified asphalt (CRMA) with waste oil, six models of asphalt with various rubber dosages were developed using Materials Studio software, and the molecular dynamics performance of the system was further examined. Then, the fatigue and high- and low-temperature performances of the CRMA binders were characterized by dynamic mechanical experiments in the laboratory. The mean square displacement and diffusion coefficient were used to quantify the migration of molecules. The aggregation state of the components was evaluated using a radial distribution function. The bulk modulus of the CRMA models was calculated to study the mechanical properties. Dynamic shear and bending beam rheometer tests were implemented to evaluate the road performances of the CRMA binders. The results show that increasing the amount of powder could improve the mechanical properties of the asphalt, that is, the modulus of 70% of the asphalt was improved by 57.5%. The rubber and waste oil were evenly dispersed in the system, and the distribution of asphalt components was in accordance with the colloid theory. The temperature-sensitive properties of the rubber led to the improvement of road properties of the CRMA binders with the increase of the admixture. Combined with the distribution of molecules in the asphalt model, the results of rheological indexes show that the waste oil could improve the rheology and stability of binders. This will provide theoretical support for upgrading the content of crumb rubber in CRMA binders.