On enhancing the performance of modified bitumen through the synergistic mechanism of polyurethane and waste rubber powder

Despite advancements in bitumen technology, traditional bitumen often fails to meet the increasing demands for durability and environmental sustainability. In this study, thermoplastic polyurethane (TPU) and waste rubber powder (WRP) were utilized to prepare a composite-modified bitumen to overcome the performance limitations of conventional bitumen. The performance of this composite-modified bitumen was comprehensively evaluated through rheological tests, thermal stability tests, infrared spectroscopy, and micro-morphological analysis. Molecular dynamics simulations revealed the molecular-level interactions between TPU and WRP, further explaining the enhancement mechanisms. The study showed that WRP undergoes a crosslinking reaction at high temperatures, enhancing the thermal stability of the composite-modified bitumen, while the elasticity of TPU promotes a microlevel interlocking mechanism that improves mechanical properties and deformation resistance. The optimal mixing ratios of TPU to WRP were determined to be 8 % and 10 %. The three-dimensional network structure formed by the long polymer chains of TPU as the main framework, interspersed with WRP, effectively optimizes the temperature stability and elastic recovery of the bitumen. This study not only fills a critical gap in research on the synergistic effects of TPU and WRP but also provides a theoretical and experimental foundation for developing low-noise, durable bitumen pavements.