Evaluation Of Particle Segregation Of Paving Asphalt Mixture And Its Influence On Pavement Performance

The segregation of asphalt mixture particles is one of the main reasons for the early disease of asphalt pavement,such as pits,rutting,etc.,which greatly reduces the performance and service life of asphalt pavement.The segregation makes the technical indicators of asphalt mixture deviate from the design value,thus speeding up the damage of pavement.Therefore,it is of great practical value to study the evaluation index of asphalt mixture segregation and the influence of segregation on pavement performance of asphalt mixture.Paving process of asphalt pavement,this paper particles segregation phenomenon happened in indoor simulated the fine aggregate segregation,coarse aggregate,mild,moderate,severe four different degree of gradation segregation of asphalt mixture,and combined with laboratory test and theoretical analysis of quantitative evaluation index of segregation was proposed,and studied the asphalt mixture performance of different levels of segregation.According to the sampling results of asphalt mixture,the gradation of mixture with different segregation degrees was determined,and the corresponding asphalt-stone ratio was calculated through the effective asphalt film thickness.The volumetric parameters of asphalt mixtures with different segregation were studied by laboratory tests,and the gradation composition was analyzed by grey correlation analysis method.According to the change of volume parameters,the segregation evaluation index based on the voidage of asphalt mixture was put forward.Under the condition of uniform distribution of aggregate,the coefficient of variation of static moments was taken as the segregation evaluation index according to the calculation method of four sides of static moments.The effects of segregation on the construction workability,compaction characteristics,bending and tensile resistance,rutting resistance at high temperature,cracking resistance at low temperature and water damage resistance of asphalt mixture were quantitatively analyzed through laboratory tests.The fatigue cracking resistance of asphalt mixture with different segregation degrees was studied through four-point bending fatigue test.Triaxial creep tests under repeated load were carried out to study the permanent deformation resistance of asphalt mixture with no segregation and medium segregation of coarse aggregate under three temperatures and three deviator-stress conditions.The indexes used to quantitatively evaluate the particle segregation of asphalt mixture were obtained by laboratory simulation test and theoretical analysis.When coarse aggregate segregation occurs in asphalt mixture,the construction workability becomes worse.The same compaction work can not reach the prescribed degree of compaction;The mechanical strength of bending pressure was significantly reduced.With the increase of segregation degree,the water stability decreases greatly.The rutting resistance at high temperature increased slightly at mild and moderate segregation,while the high temperature stability decreased at severe segregation.Under low temperature,the ultimate strain of bending and tension decreases to different degrees.Fatigue crack resistance decreased slightly at mild segregation,decreased by half at moderate segregation,and greatly decreased at severe segregation.The permanent deformation resistance decreased significantly after moderate segregation.Fine aggregate segregation has little effect on workability,water stability,bending tensile properties and fatigue properties of asphalt mixture,but rutting resistance of asphalt mixture is significantly reduced at high temperature,and cracking resistance is slightly decreased at low temperature.In the process of production,transportation,spreading and rolling of asphalt mixture,the causes and influencing factors of segregation are analyzed,and the prevention measures of segregation are put forward.Mixture segregation makes asphalt pavement appear various forms of early damage,which not only increases the cost of pavement early maintenance,but also shortens the service life of pavement.Therefore,it is of great significance to evaluate the segregation of asphalt mixture and study the influence of segregation on the pavement performance of asphalt mixture.