Permanent Deformation Behavior Of Asphalt And Asphalt Mixtures And Its Simulation Analysis

Due to heavy load,overload,canalized traffic and summer high temperature,asphalt pavement tends to produce rutting diseases,which seriously affect the smoothness,driving safety and comfort of asphalt pavement;meanwhile,the further development of rutting will also cause net crack,pit slots and other diseases,which seriously affect the structural performance and serviceability of asphalt pavement.Therefore,the rutting of asphalt pavement has always been a hot scientific issue at home and abroad.In this paper,the permanent deformation characteristics of asphalt binder（asphalt,mastic,mortar）and asphalt mixture are studied respectively.At the same time,the rutting development of asphalt pavement is simulated by the combination of test results and Finite Element Modeling（FEM）.Firstly,the Dynamic Shear Rheometer（DSR）was used to conduct the multi-stress creep recovery test（MSCR）for asphalt,mastic and mortar.The permanent deformation property of three kind of asphalt binder were studied,and the relationship between high temperature performance of asphalt binder and rutting performance of mixture were also studied.The experimental results show that the unrecoverable creep compliance（Jnr）of asphalt,mastic and mortar show the power function increases with the increase of temperature,while the creep recovery rate decreases with the increase of temperature;at the same condition the anti-permanent deformation capacity of the mortar is greater than the mastic and asphalt,compared to the Jnr value of the asphalt,compared with asphalt,the high temperature performance of mastic and mortar improves 5-10°C and20°C,respectively;the Jnr value of mastic was reduced by 70%⁸5%and mortar was reduced by more than 99%;the Jnr values of asphalt binders show a power function relationship with the rutting of the mixtures,when the Jnr value of asphalt,mastic and mortar were less than 0.383 kPa^-1,0.082 kPa^-1,0.0031 kPa^-1 respectively,the corresponding asphalt mixture show better rutting performance,can be used in heavy traffic roads.Secondly,the uniaxial repeated creep test and the wheel track test（WTT）were used to investigate the permanent deformation of the asphalt mixture.The influence of temperature,load and water on the rutting development of the asphalt mixture was studied;the three-stage permanent deformation characteristics of the asphalt mixture were analyzed;and the influence of multi-stress on the rutting development of asphalt mixture was also studied.The results show that the temperature has the greatest influence on the rutting development of asphalt mixture,followed by water and load.The transition point of the first and second stages rutting‘Fs’and the flow number F_N had a strong linear relationship,Fs can also be a rutting indicator of asphalt mixtures;and the rutting rate of the three stages also have a strong linear relationship,with the increase strain rate of the initial stage,the strain rate of the latter two stages also increases;furthermore,in the multi-stress wheel track test,the larger the load,the larger the deformation rate,and the rutting caused on the first stage is the largest,followed by the second stage and the third stage,they are independent of the load order.The initial load of asphalt pavement has a greater impact on the development of rutting.Finally,based on the time-hardening creep model the rutting development of the asphalt mixture was simulated by using the finite element analysis software.The results show that the creep model parameters of asphalt mixtures can be determined by fitting the wheel track testing data,and the range of parameters A,n and m was 1.4×10^-3 to7.5×10^-3,0.5 to 1.3,and-0.6 to-0.8 respectively;by applying a correction coefficient in the range of 1.2 to 1.5 for the parameter A can make simulation more reliable.Meanwhile,the finite simulation results of the multi-stress testing well describe the development of the rutting evolution to the asphalt mixture under different loads.At the same time,the simulation results of rutting evolution to the pavement structure show that the rutting depth of middle layer was the largest,which are consistent with the calculation results of the asphalt pavement permanent deformation checking model in the specification,and was accord with actual road rutting depth,can be used to predict the rutting development of asphalt pavement under complex traffic conditions.