Study On Micromechanics Model For Asphalt Concrete Based On Aggregate Inlay And Extrusion

Asphalt mixture is a kind of multiphase composite viscoelastic material.Its basic viscoelastic properties mainly depend on the composition of mixture material and its internal microstructure.It is of great significance for the integration of the material design of asphalt mixture and the structural design of asphalt pavement to use the composite micromechanics to explore the influence of the micromechanics and structural composition of asphalt mixture on its mechanical properties,and to establish a mathematical model to predict the mechanical properties of asphalt mixture.In order to accurately predict the viscoelastic parameters such as dynamic modulus and phase Angle of asphalt mixture through mathematical physical model,it is necessary to verify the validity of the model by comparing the experimental data with the predicted data,and analyze the influence of the model parameter value on the prediction results,as well as the influencing factors of the model parameter value.In this paper,based on self-consistent micromechanics model proposed by Luo,the effect of the gradation for the mixture on its dynamic modulus is taken into account,and the mixture is considered as consisting of a number of aggregate particle units wrapped with a certain asphalt film,and the dynamic modulus prediction model based on the grading design is established.Four kinds of asphalt mixtures are designed to verify the validity of the model.The results show that the determination coefficients of the model and the measured data are both above 0.98,which indicates that the model has a good accuracy in the prediction of dynamic modulus.Than,in order to evaluate the viscoelastic mechanical properties of asphalt mixture,the phase Angle of mixture should be predicted in addition to the dynamic modulus of mixture.The self-consistent model is extended in the complex domain,and the complex number micromech model is established.By predicting the storage modulus and loss modulus of the mixture,the dynamic modulus and phase Angle of the mixture can be predicted at the same time.The effectiveness of the model was verified by four forward mixes using a forward model and a reverse model.It is found that there is a big gap between the same aggregate modulus in different mixtures calculated by the reverse model.Through the analysis of the model,the defect was attributed to the fact that the model did not take into account the strengthening effect of aggregate intercalation and extrusion on its mechanical properties.To this end,the model is modified by introducing aggregate inlay factor,and the micromechanical model of asphalt mixture based on aggregate inlay is derived.Through the embedded modulus,the model was verified by four kinds of asphalt mixture.It was found that the same aggregate modulus was consistent in different mixtures calculated by the inverse model after considering the aggregate intrusion.The prediction results of dynamic modulus and phase Angle predicted by forward model changed with the change of p value and q value in the embedding factor.The values of p and q are chosen to be 0.01,0.1,0.5,1,2,5,7,and 10,respectively,and the dynamic modulus and phase angle master curves are analyzed at 20 ℃.Under the condition of p = 1,the predicted dynamic modulus master curve fluctuates less with the change of q value,and the phase angle curves at the top when q = 0.01;while under q=1,the dynamic modulus master curve has a gap at the low frequency and basically coincident at the high frequency,while the master curve of phase angle shows a larger p-value and a more regular curve.Finally,in order to further study the model parameters,seven different gradation types of asphalt mixture were selected to qualitatively analyze the influence of gradation types on the p value and q value in the model nesting factor.The results show that the larger the nominal maximum particle size of aggregate is,the larger the p value and q value of nesting factors,and the increase of void ratio will lead to the decrease of p value and q value of nesting factors,the more coarse aggregates in the grading,the more obvious the degree of intrusion,the greater the p and q values.At the same time,AC-13 mixture was selected to conduct different times of abrasion of the aggregate,and the influence of the aggregate’s apparent characteristics on the model’s nesting factor was quantitatively analyzed.The results show that with the increase of abrasion times,the sphericity of the aggregate increases,the angularity and texture index decrease,and the extrusion factor of the mixture obtained by molding also decreases,and it changed linearly with the sphericity,texture index and angularity index.