Green environmental protection and sustainable utilization of straw: Investigation for molecular dynamics of highland barley straw fiber to enhancing road performance of asphalt

This study explores the impact of highland barley straw fiber (HBSF), an environmentally friendly material, on the molecular dynamics and performance of asphalt. Despite the widespread use of fibers in enhancing asphalt performance, molecular-scale investigations are lacking. In this study, molecular dynamics software was employed to model matrix asphalt and three types of HBSF-modified asphalt with varying cellulose contents (8.62wt%, 15.88wt%, 22.06wt%). Thermodynamic parameters mean squared displacements (MSD), radial distribution function (RDF), free volume fraction (FFV), and mechanical parameters were analyzed through simulation to understand the diffusion behavior of highland barley straw cellulose molecules in asphalt and study the modification mechanism. The findings revealed that the 8.62wt% cellulose-modified asphalt had the slowest diffusion rate, with the most favorable temperature for asphalt diffusion being 298.15 K. Integration of highland barley straw cellulose molecules facilitated the self-aggregation process of asphaltene-asphaltene and improved the compatibility between asphaltene-resin, resulting in asphalt stabilization. However, the study found that moisture damage weakened the water resistance of highland barley straw cellulose-modified asphalt binder. Specifically, modifying asphalt with 8.62wt% cellulose increased the Young modulus by 28.37%, bulk modulus by 39.77%, and shear modulus by 26.45%, demonstrating the overall improvement achieved with the combined effect of 8.62wt% highland barley straw cellulose-modified asphalt. These findings have significant implications for repurposing highland barley straw as a solid waste material and enhancing the low-temperature crack resistance of asphalt binders.