Macro-micro Analysis For Fracture Characteristics Of Asphalt Mixture Using DEM At Low-temperature

As a type of multi-phase composite materials,microscopic structure of asphalt mixtrues has a signifcant impact on the fracture performance at low-temperature.These indexes are diffcult to mesure through lab tests,and there are complex process and large workload in conventional lab tests.Hence,studying the low-temperature fracture behaviour of asphalt mixture using numerical test method has practical significance.The following studies were carried out in this paper:(1)Loading modes of SCB lab test were determined through analyzing test parameters.Based on this,macroscopic fracture characteristics of asphalt mixtures are investigated at different temperature and fracture loading modes from a view of the fracture toughness,the time corresponding to peak time and the crack length.(2)DEM numerical method including a physical model based on random algorithms and an improved microscopic contact constitutive was built.The contact constitutive has the same mathematical structre under different loading conditions,which brings improved simulation accuracy.(3)SCB numerical test method was built based on Fish codes and verified through lab tests,which can reproduce the whole process of SCB tests.(4)The impact of microscopic structure including geometric characteristics and distribution of voids and aggregates on fracture properties and crack development laws are revelled using numerical test method through changing porosity,void size,void distribution,aggregate orientation,aggregate flatness ratio,aggregate content and aggregate distribution.(5)Aggregate structure characteristics were revealed through contact force network.The impact of different constituents on mastic properties was analyzed through orthogonal design.An optimized gradation of asphalt mixtures was put forward and verified.