Study On Dynamic Viscoelastic Model And TSRST Test Of Superpave Asphalt Mixture

With the increase of passenger and freight volume of asphalt pavement,it is developing towards large-scale and heavy-duty.In recent years,Superpave Asphalt pavement has been widely used in asphalt pavement construction.In this paper,based on the Haibowan belt project of the 217 provincial road in Wuhai City,Inner Mongolia,two Superpave Asphalt Mixtures（sup-13 and sup-20）are designed,the dynamic modulus test and thermal stress restrained specimen test（TSRST）are carried out,the HS dynamic viscoelastic models of the two Superpave Asphalt Mixtures are established,and the HS models are transformed into GKV and GM models.Finally,GM model is applied to tspave asphalt mixture TSRST finite element numerical simulation,and compared with TSRST curve.The main contents and achievements of this paper are as follows:（1）According to the Superpave volume design method and the supporting project,three（coarse,medium and fine）composite gradients are designed for the two mixtures to determine the design gradation and the optimal asphalt content.The results show that the design gradation of sup-13 and sup-20 asphalt mixtures is 2（medium）;The optimum asphalt content of sup-13 and sup-20 asphalt mixtures is4.66% and 4.19% respectively;The water stability of the two asphalt mixtures meets the Superpave standard.（2）Uniaxial compression dynamic modulus tests of two asphalt mixtures were carried out at five test temperatures and seven frequencies;The grey correlation degree method is used to analyze the grey correlation degree of the influencing factors on the test results of two kinds of asphalt mixtures.The results show that the dynamic modulus and storage modulus of the two asphalt mixtures increase with the increase of frequency and the decrease of temperature,while the change trends of phase angle and loss modulus with frequency at different test temperatures are inconsistent.The dynamic modulus,storage modulus and loss modulus of sup-20 are greater than that of sup-13,and the difference of phase angle between the two mixtures is small;Under the test conditions,the test frequency is the main factor affecting the dynamic modulus,storage modulus and loss modulus,and the test temperature is the main factor affecting the phase angle.（3）Based on the time temperature equivalence principle,the HS viscoelastic model and WLF shift factor are used to establish the viscoelastic master curves of two kinds of asphalt mixtures（sup-13 and sup-20）when the reference temperature is20 ℃,and the HS model parameters and WLF shift factor are determined by the least square method;The HS model is transformed into a generalized GKV and GM model with three parameters,and compared with the viscoelastic master curve of the HS model.The results show that HS model can accurately describe the dynamic viscoelastic mechanical behavior of two asphalt mixtures in a wide range of temperature and frequency,and there are few experimental parameters to determine the model,so the fitting parameters obtained have certain physical significance;HS model can be transformed into GKV and GM models,and GKV and GM models with11 parameters can better describe the viscoelastic dynamic characteristics of the two asphalt mixtures.（4）The TSRST of the two asphalt mixtures has small group variability.The relaxation ability of sup-13 asphalt mixture in the first stage with stress relaxation is better than that of sup-20 asphalt mixture.At the same temperature,the temperature stress of sup-20 is greater than that of sup-13 asphalt mixture.（5）The finite element model of TSRST is established by ABAQUS software,and the prony series obtained by GM model is used as the viscoelastic input parameter to carry out the finite element numerical calculation under three cooling rates,and the results are compared with those measured by TSRST.The results show that the TSRST curve of the two asphalt mixtures is in good agreement with the numerical simulation curve in the first stage with stress relaxation during the continuous cooling process.The slope of the TSRST curve is slightly different from the numerical results in the second stage without stress relaxation because the temperature difference inside and outside the specimen is not considered in the numerical simulation process.The greater the cooling rate,the weaker the relaxation capacity of asphalt mixture,and the faster the stress accumulation.However,the change of cooling rate has little effect on the slope of stress-free relaxation stage,which verifies the HS model.