Four kinds of polyurethane(PU)prepolymers and one kind of isocyanate monomer were used to modify the base asphalt.The isocyanate(—NCO)content of five samples was determined by toluene/di-n-butylamine and hydrochloric acid standard titration solution method.The mechanism and microstructure of PU prepolymer-modified asphalt were analyzed by Fourier transform infrared spectroscopy(FTIR)and fluorescence microscope.The effect of—NCO content on the rheological properties of PU-modified asphalt was analyzed by dynamic shear rheology(DSR)test.Using AC-13 gradation,the high-temperature rutting test and low-temperature trabecular bending test were carried out on the modified asphalt mixture.The results showed that PU prepolymer-modified asphalt had a chemical modification phenomenon and the increase of—NCO content could improve the high-temperature rheological properties of modified asphalt and the dispersion of the system.The low content of—NCO in PU prepolymer could make the high-temperature performance of the asphalt mixture worse,and the excessive content of—NCO could also increase the brittleness of the mixture.
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