Study On Rutting Resistance Of SFP-20 In Middle Surface Of Asphalt Pavement

Asphalt pavement is a typical form of pavement structure in our country,and the pavement performance of ordinary asphalt mixture is poor under the action of high temperature and heavy traffic.Rutting is one of the diseases of traditional asphalt concrete pavement.Rutting is mainly caused by shear flow in high temperature environment of asphalt mixture,so road workers have been using modified asphalt to alleviate it.The long-term effect of the existing rutting disease is not satisfactory,so a kind of pavement mixture which can meet the high temperature stability is urgently needed.Semi-flexible composite material is a kind of composite material with the advantages of asphalt concrete and cement concrete.It has excellent shear resistance at high temperature.At home and abroad,semi-flexible composite material has been widely used in the upper layer of asphalt pavement structure,and good results have been achieved.Through a lot of research,it is concluded that the rutting is mainly caused by the fact that the shear resistance of the surface layer in the pavement structure can not meet the requirements,and the semi-flexible composite material applied in the middle layer can meet the shear strength of the middle layer of the asphalt pavement.Therefore,this paper will take improving the rutting resistance of the asphalt pavement structure as the core objective,and apply the semi-flexible composite material to the asphalt pavement structure.And some achievements have been achieved.First of all,based on a large number of domestic and foreign literature,this paper carries out a finite element modeling for the typical asphalt pavement structure of high-grade pavement.Through the analysis of the size of the shear stress peak and the distribution area of the average shear stress,it can be concluded that: first,the shear stress peak in the asphalt pavement structure increases first and then decreases in the surface layer,and the shear stress peak under different thickness of the asphalt pavement all occur in the middle surface layer.Secondly,in the same pavement structure,the mean value of shear stress of the middle layer is the largest,which is14.8% higher than that of the upper layer and 43.1% higher than that of the lower layer.Therefore,comprehensive analysis of the peak value of shear stress,thenumerical value and distribution of the mean value of shear stress in the asphalt pavement structure shows that the middle layer exists as anti-rutting layer in the asphalt pavement structure and fundamentally solves the problem of the road.For surface rutting,it is necessary to study a mixture with high shear strength for middle surface layer.Aiming at the research of rutting resistance layer of asphalt pavement structure,this paper uses SFP-20 mixture for middle layer,while SFP-20 semi-flexible composite mixture is designed to meet the performance requirements.The first step is to design three kinds of matrix asphalt mixture with void ratio of 22%,25% and 30%by grading mixing method and volume method based on particle interference theory,and through comprehensive flying test and leak analysis test.The optimum asphalt-aggregate ratio of the parent asphalt mixture is obtained.The second step is to prepare high performance cement mortar according to the requirement of semi-flexible mixture grouting and dry shrinkage and low temperature shrinkage of cement slurry,and to preliminarily determine the mix ratio of cement mortar.In the last step,the asphalt mixture and cement grouting material were prepared,and the grouting rate was tested.The average grouting rate was 95%,and the grouting effect was good.Finally complete the SFP-20 mixture on grouting in 22%,25% and 30%respectively under the void fraction,experimental study on the mechanical properties and road performance test including uniaxial penetration test,indirect tensile test,bending creep test and modulus of resilience test,freeze-thaw splitting test,low-temperature bending test and rutting test,the test results show that a flexible mixture performance is far beyond the traditional AC-20 asphalt mixture,especially under the environment of high temperature deformation of shear resistance and high temperature resistance ability,According to the road performance index of semi-flexible mixture with different voids,the suitable voids range is 22%?25%.According to the results of laboratory test,the discrete element under the theory of virtual uniaxial penetration test,indirect tensile test and virtual rutting test,and to establish a discrete element model,using 3d laser scanning technology for the external characteristics of aggregate,and using geometry command imported into the software internally generated aggregate,on the basis of the generated virtualaggregate software used to own Bubble Pack algorithm to generate virtual specimens,by using the method of inverse calculation of "drills" to the assignment of model,and simulated the whole process of the three trials,reveals its failure mechanism from the mesoscopic level.Finally,the virtual rut test is improved on the basis of the previous three virtual tests,and compared with the traditional asphalt pavement model,it shows that the SFP-20 mixture has excellent road performance.