Influence of polyurethane-precursor-based reactive modifier on microstructure and micromechanical properties of bitumen by finite element simulation

As traffic demand continues to rise, the use of liquid chemical materials, such as polyurethane precursor-based reactive modifiers (PRM), to replace traditional bitumen modifiers presents a dual benefit. It not only contributes to decarbonization by reducing production temperatures and costs but also enhances pavement performance. This study aims to investigate the impact of PRM on the microstructure (comprising bee and interstitial phases) and the micromechanical response of bitumen using the finite element (FE) method. The microstructure FE models of polyurethane precursor-based reactive modified bitumen (PRMB) were developed from Atomic Force Microscopy images, and the micromechanical responses of PRMB with various PRM contents were analyzed. The findings indicate that the load-bearing capacity of the bee and interstitial phase first decreases and then increases as the PRM content increases. Meanwhile, the magnitude of von Mises stress increases with higher modifier content, with a more pronounced amplification in the bee phase compared to the interstitial phase. Furthermore, the modifications lead to a reduction in the tensile deformation ratio of bitumen. This research enhances the understanding of how PRM influence the microstructure and micromechanical properties of bitumen.