Research On Properties Of Polyurethane (PU) Modified Asphalt And Mixture For Deck Pavement

This paper developed a new type of material suitable for steel bridge deck pavement structure-polyurethane(PU)modified asphalt,aiming to solve the existing problems of the bridge deck pavement materials,and verified the technical issues involved in PU modified asphalt and its mixtures: systematically studying the formulation system,rheological properties,modification mechanism and road performance of PU modified asphalt mixture,by a series of laboratory tests.In this paper,two kind of different types of polyurethane resin were used to modify the 70# matrix asphalt,the optimal dosage of each component and the curing temperature were determined by tensile test,segregation test,fluorescence microscope test and Brookfield viscosity test.Finally,the optimal dosage of the two PU modified asphalt were:45%JM-PU,4% compatibilizer,12% chain extender,3% coupling agent and 3% thinner;40%JZ-PU,3% compatibilizer,12% chain extender,4% coupling agent and 4% thinner;and the curing temperature of the two PU modified asphalt was 130°C.The rheological properties of the two kinds of PU modified asphalt with different amounts of polyurethane were studied by DSR and BBR tests.It was found that:the high temperature performance,low temperature performance,temperature sensitivity and load frequency of the two kinds of modified asphalt were improved by polyurethane;but with the increase of resin content,the high temperature properties of the two modified asphalts will increase to a certain extent,the low temperature performance will decrease to a certain extent.When the polyurethane dosage is 45%,JM-PU modified asphalt will achieve the best temperature performance;when the polyurethane dosage is 40%,JZ-PU modified asphalt reaches the best temperature performance.The modification mechanism,thermal stability and micro-morphology of two kinds of PU modified asphalt were studied by FTIR,TGA,and AFM.The results of FTIR showed that:there were new absorption peaks in the FTIR spectra of the two PU modified asphalts,and the modification mechanism of the two kinds of PU modified asphalts were chemically modified;the results of TGA showed that: the thermal stability of the asphalt was improved by the two polyurethanes,and the JZ-PU had a better effect on it;AFM results showed that: the composition of the asphalt molecules was changed by the two kinds of polyurethanes,and the overall length of the “bee” structures was elongated,the height was reduced and the rigidity was impoved,in the two kinds of PU modified asphalt.The strength and road performance of the two kinds of PU modified asphalt mixtures was studied through a series of laboratory tests.The results showed that: the JM-PU modified asphalt has high flexural tensile strength,good high temperature stability,great low temperature crack resistance,fatigue crack resistance and aging resistance;and JZ-PU modified asphalt mixture has higher strength and high temperature stability than JM-PU modified asphalt mixture.But the water stability of the two kinds of PU modified asphalt mixtures is poor,it can be improved by adding a suitable amount of liquid anti-stripping agent in its.