Discrete Element Numerical Simulation Of Hot Recycled Asphalt Mixture Based On Indirect Tensile Test

Recycled mixture is a kind of discontinuous material with complex composition,and the relationship of macro-properties and microstructure are closely,but at present,the research on the microstructure characteristics of recycled asphalt mixture is less.From the perspective of microstructure,some research project interpreted the process of damage,and researcher analyzed the law of recycled asphalt mixture damage,then those research achievements realized the consolidate of microstructure and macroscopic proper.Through those methods,not only the micromechanics became a effective supplement to the traditional indoor test,but also it can theoretically guide the selection of laboratory methods.Therefore,using the discrete element method constructed the microstructure model of recycled asphalt mixture,and it realized the combine of traditional laboratory test and numerical analysis.This method had important theoretical significance.In this paper,firstly,chemical staining was used to dye those new aggregates,then forming some Marshall standard specimens,which was mixed different rate of reclaimed asphalt pavement,indirect tensile test was used to test those specimens' splitting strength.Secondly,using the digital camera obtained the specimen cross section,the image processing technologies were applied to achieve those purposes of highlighting images' detail and complete the classification of aggregates' image size.Thirdly,the stereology method was used to transform from two-dimensional solid to two-dimensional solid about the cross section image,and the uniformity of image particles was calculated.Lastly,according to those above analysis results,gradation of recycled mixture was reasonably determined in the two-dimensional discrete element model,and the numerical model of recycled asphalt mixture was reconstructed.In this model,the actual boundary information and reasonable material micro parameters was used,through the use of servo mechanism,the loads was controlled,the numerical simulation of indirect tensile test was accomplished and the micromechanics characteristics of recycled asphalt was analyzed.The results show that:(1)at blending ratio of 0%,10%,20%,40% about reclaimed asphalt pavement,the splitting strength were 1.57 MPa,1.43 MPa,1.38 MPa,1.33 MPa,and splitting strength with blending rate was decreased,the blending ratio of 10%,20%,40% of specimen strength decreased rate were 8.9%,12.1%,15.3%.(2)Using stereology method corrected the gradation of aggregates in image,the aggregate coefficient was ?/4 and 0.86.the coefficient made the image gradation and aggregate gradation design was consistent;(3)the aggregate uniformity coefficient reached 0.9,it showed that transverse distribution was evenly.there was a linear relationship between the distribution of old and new aggregates in chi square fitting trend chart,those results proved that the old and new aggregates spatial distribution reached a uniform state;(4)Though simulation results of indirect tensile test existed some errors,from the micro perspective,the velocity vector diagram and evolutionary law of the force chain were explained in the numerical model,and the results proved the simulation of the recycled asphalt mixture was effective.