Study on Performance of Polyurethane Prepolymer Modified Asphalt with Different Isocyanate Content
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.