Virtual Indirect Tensile Test Of Asphalt Mixture Based On Computer Tomography Scanning Technology

Asphalt mixture is a kind of three-phase composite composed of asphalt mortar,aggregate and void.On account of the different materials,construction equipment and load conditions,the mechanical properties of the mixture will become more complex,and it is not easy to find the change law in the project test.In order to overcome the limitations of traditional methods,the research on the performance of asphalt mixture has gradually turned to its heterogeneity and microstructure.This paper established virtual indirect tensile test based on CT(Computer Tomogrphy)scanning technology and finite element method,and used numerical method to study the mechanical properties of asphalt mixture.Firstly,the microstructure image of asphalt mixture was obtained based on CT scanning technology,and the two-dimension numerical model of asphalt mixture including aggregate,asphalt mortar and void is established by combining digital image processing technology and finite element method.The viscoelasticity of asphalt mortar was described with Burgers model,the viscoelastic parameters were obtained through creep test and input into the ABAQUS software to establish the virtual indirect tensile test.The accuracy of the finite element method was verified by taking the splitting stiffness modulus as the verification index of the virtual test,and the error of the comparison with the indoor test was no more than 10%.Secondly,taking the stress concentration parameter and splitting stiffness modulus as evaluation index,the influence factors of indirect tensile test of asphalt mixture were analyzed by numerical method.The result shows that the stress concentration parameter and the splitting stiffness modulus of AC-20 mixture is larger than that of AC-13 mixture,indicating that the tensile property of AC-13 mixture is better than AC-13 mixture;with the same gradation,the different distribution of aggregate will affect the internal stress distribution of asphalt mixture;the variety of asphalt will affect the deformation resistance of asphalt mixture;the change of loading rate will result in the change of splitting stiffness modulus of asphalt mixture;the existence of voids will lead to the increase of stress concentration parameters of asphalt mixture,which is more likely to lead to stress concentration and reduce the crack resistance of asphalt mixture to a certain extent.Then,in order to study the effect of aggregate microstructure on the mechanical properties of asphalt mixture,the motion trajectory and shape characteristics of coarse aggregate were analyzed.With the help of Image Pro Plus,it was found that the aggregate will have translation and rotation phenomena under the splitting load,and the flat momentum and rotation angle of AC-13 mixture were larger than that of AC-20 mixture,the influence of graduation on the tensile performance is analyzed from the perspective of microstructure.Finally,the correlation between different aggregate shape evaluation indexes and the splitting stiffness modulus ofasphalt mixture was analyzed,it was founded that the splitting stiffness modulus increases with the increase of the angular index,and the angularity index of AC-13 mixture is smaller than that of AC-20 mixture on the whole,indicating that the microstructure of aggregate will affect the tensile performance of asphalt mixture.