Research On Road Performance Of Polyurethane Modified Asphalt And Its Mixture

With the influence of heavy load and channelized traffic,ordinary asphalt is more difficult to meet the requirements of traffic development.,and high-quality modified asphalt has been sought in engineering.Although SBS modified asphalt has good comprehensive properties,it has strong selectivity to matrix asphalt,and there are some problems in thermal storage stability.In recent years,poly(phosphoric acid)(PPA),vinyl reactive terpolymer(RET),polyurethane(PU)and other modifiers which can react with asphalt have gradually come into our field of vision.Polyurethane modified asphalt has the advantages of good thermal stability,obviously improving the high temperature performance of asphalt,but at present,most of the polyurethane used in the research is solid,which is not easy to disperse in asphalt,and can achieve better modification effect when the content is large.In this paper,the preparation technology of liquid polyurethane(I-PU)modified asphalt with the content of 0% ? 4% and the changes of three indexes before and after aging,rotational viscosity,storage stability and shear rheological properties were studied.The results show that polyurethane modified asphalt has good high-temperature stability,better rut resistance,anti-aging performance and lower temperature sensitivity.Polyurethane has good compatibility with asphalt,and its viscosity meets the requirements of construction technical specifications.Secondly,atomic force microscopy(AFM)was used to analyze the micro morphology of polyurethane modified asphalt before and after aging;differential scanning calorimetry(DSC)was used to determine the glass transition temperature and analyze the aggregation state of components in asphalt;FTIR was used to analyze the modification mechanism of polyurethane modified asphalt.The results showed that polyurethane had a chemical reaction with asphalt and produced new functional groups.The heat flux curve of polyurethane modified asphalt changed more flatter,glass transition temperature was lower,and had better temperature sensitivity and low temperature performance.Polyurethane addition changed the composition of matrix leachate,and polyurethane had better aging resistance.Then,AC-13 type grading type is selected to prepare the recommended content of polyurethane modified asphalt mixture.SBS and matrix asphalt samples are formed at the same time.The rutting test and Hamburg immersion rutting test,the bending test of the mixture beam,the immersion Marshall and freeze-thaw splitting test,the long-term aging test of the mixture and the dynamic modulus test are carried out respectively.The experimental results show that the polyurethane modified asphalt mixture has better rut resistance,low temperature stability and aging resistance than the base asphalt.The dynamic stability of 2% polyurethane modified asphalt mixture is similar to that of SBS,but its water resistance ability is insufficient.Finally,the adhesion of asphalt and aggregate is evaluated by the method of combining boiling with scanning electron microscope,and the surface morphology and roughness of the sample are observed by AFM to explain the failure behavior of the water stability of asphalt mixture.The best content of hydrated lime is determined to be 25% by replacing part of mineral powder with different content of hydrated lime,respectively forming the test pieces of immersion Marshall and freeze-thaw splitting At this time,the freeze-thaw cleavage increased by 13.07%.Finally,the performance of polyurethane modified asphalt mixture with hydrated lime was verified.The results show that the high temperature stability,low temperature crack resistance,water stability and other road performance of the mixture can meet the requirements of the construction technical specifications.