Rheological properties and micro-characteristics of polyurethane composite modified asphalt

The objective of this study aims to investigate the rheological properties and micro-characteristics of polyurethane (PU) composite modified asphalt. In this study, the mixture of PU and rock asphalt (RA) was incorporated into base asphalt to prepare PU composite modified asphalt through a self-determined laboratory process. The properties of PU composite asphalt with different PU and RA contents was analyzed by the base performance tests. The dynamic shear rheology (DSR), bending beam rheology (BBR), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermal gravity (TG) were used to clarify rheological properties, chemical and microstructure of the binders, respectively. The results indicated that the PU composite modified asphalt with 5% PU and 5% RA exhibited a favorable performance in terms of the penetration, ductility, softening point and rotational viscosity, respectively. The PU composite modified asphalt with 3%, 5% PU and 15% RA showed the best high temperature performance grade (PG). Both the PU and RA indicated a preferable compatibility with the base asphalt. The unsaturated bond in PU crosslinked with the S-S bond in asphalt, which is helpful to improve the resistance to low temperature deformation. It can be found that the composite asphalt containing 5% PU and 5% RA performed a preferable laboratory performance investigated based on rheological properties tests and the microstructure observation. Also, the isocyanate respectively reacted with the phenol and carboxylic acid in the PU composite modified asphalt leading to the performance improvement. This study also showed that the PU has promising properties, and the PU and RA can be used as composite modification to increase the durability and service life of asphalt pavement