A comparative study of the properties CO2-based polyurethane modified asphalts prepared by prepolymer and in-situ polymerization methods

•PPC-PU prepolymer and PPC-PU were successfully prepared.•P-PUMA and I-PUMA can be cured in natural environment, with a curing rate higher than 80 % after curing for 15 d.•PPC-PU and its prepolymer have good compatibility with asphalt.•PPC-PU and its prepolymer improve the high and low temperature performance of asphalt. Polyurethane (PU) modified asphalt has become a hot research topic, but the PU used is usually synthesized from non-renewable petroleum resources. In this paper, the feasibility of using environment-friendly polyurethane to modify asphalt by prepolymer and in situ polymerization methods and the curing properties of the PU modified asphalts in natural environment were studied. CO2-based PPC-PU prepolymer and PPC-PU were prepared with poly (propylene carbonate) diol (PPC). The Fourier transform infrared spectroscopy and thermogravimetric analysis were used to examine their chemical structures and thermal characteristics. Then, PU modified asphalts were prepared by prepolymer and in situ polymerization methods respectively and cured in natural environment for different periods. After that, the chemical functional groups, physical properties, storage stability, low temperature and high temperature properties of various modified asphalts were tested. The results revealed that the PPC-PU prepolymer and PPC-PU prepared had good thermal stability and could enhance the low temperature and high temperature properties of the asphalt. The PPC-PU modified asphalts can be cured in natural environment, with a curing rate higher than 80 % after curing for 15 d. The modifiers have good compatibility with asphalt. Except for the low temperature performance, the properties of the modified asphalts were gradually improved with curing. It is concluded that the environment-friendly PPC-PU and its prepolymer can improve performance of asphalt, offering a fresh concept for production of green PU modified asphalt.