Investigation of the modification mechanism of thermoplastic polyurethane composite modified asphalt

This study aims to investigate the role of thermoplastic polyurethane (TPU) in asphalt modification and its improvements to high- and low-temperature performance and fatigue resistance. To analyze the microstructural characteristics of TPU and rock asphalt (RA) composite-modified asphalt, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) were employed, revealing that the introduction of TPU forms new urethane groups (-NHCOO-) in the asphalt matrix and achieves uniform dispersion. Additionally, multiple stress creep recovery (MSCR) tests indicate a reduction in the Jnr values within the 64 degrees C to 76 degrees C range. Linear amplitude sweep (LAS) tests show that fatigue life increases by over 45 % under low-stress conditions. Bending beam rheometer (BBR) tests demonstrate that at -18 degrees C, the S value decreases by 40.4 % and the m value increases by 5.5 %. Overall, TPU significantly enhances the low-temperature flexibility and fatigue resistance of asphalt, while its combination with RA further improves high-temperature deformation recovery and durability.