Low Temperature Cracking Behavior Of Asphalt Concrete Based On Synergistic Effect Of Meso-structure

Low-temperature cracking is one of the main diseases of asphalt pavement.A complex cracking state will be gradually formed under the influence of traffic load,temperature,and other factors,resulting in irreversible material macro-performance deterioration.Meanwhile,asphalt concrete,as a multiphase composite system composed of aggregates,voids,and asphalt mastic,has a close relationship between its meso-structural characteristics and macroscopic behavior.The traditional perspective based on the aggregate gradation and porosity is difficult to meet the needs of deep cracking analysis of asphalt concrete.As a result,the related research based on the characteristics of meso-structure has become a hot spot in recent years.Mesostructural characteristics of asphalt concrete not only refers to the geometric characteristics of the mesoscopic structure itself(such as the aggregate morphology,pore size,etc.),but also includes the differences of the spatial distribution of different mesoscopic structures(such as coarse aggregate spatial location,uneven distribution of air voids,etc.).Obviously,under the certain conditions of raw materials,aggregate gradation,and total porosity,the random combination of space distribution characteristics of mesoscopic structure can provide nonnegligible effect on the crack resistance of asphalt concrete.Therefore,in-depth study of the synergistic effect of spatial combination of meso-structure on low-temperature fracture performance and crack propagation law of asphalt concrete is of positive significance for clarifying the mechanisms of low-temperature crack resistance of asphalt concrete.In view of this,aiming at the problem of low-temperature cracking of asphalt concrete,this dissertation took the combined characteristics of aggregate and void space as the entry point to carry out the following research work using semi-circular bending tests(SCB)and discrete element numerical simulations(DEM):(1)Based on SCB indoor tests,the laws of fracture toughness and crack distribution of asphalt concrete at low-temperature was analyzed at different temperatures(5 ℃,10 ℃),porosities(2%,4%,and 6%),and fracture loading modes(type I,type II,and mixed type I &type II).(2)A detailed asphalt concrete model was constructed by DEM random algorithm.The contact constitutive between different meso-structures was determined,and the corresponding parameter calibration was realized.A virtual test method for low temperature cracking of asphalt concrete was put forward after reproducing the whole process of SCB test.The reliability of the virtual test was verified by comparing with the laboratory tests.(3)12 DEM models of asphalt concrete were constructed to characterize the differences of spatial distribution and combination characteristics of meso-structure by transforming the spatial location of large particle size aggregates and non-uniform distribution characteristics of porosity.Moreover,based on the proposed virtual test method,the low-temperature fracture toughness,meso-contact force and crack distribution,and crack strike of asphalt concrete were studied under different temperatures and fracture loading modes with the changes of spatial distribution characteristics of meso-structure,thus revealing the synergistic effect of mesostructure on the low-temperature cracking behavior of asphalt concrete.The research results of this paper are helpful to deepen the understanding of the scientific problem of low-temperature cracking of asphalt concrete,and provide a certain basis for improving the anti-cracking design of asphalt concrete.