Study On Sensitivity Of Skeleton Structure Based On Particle Shape Of Aggregate In Asphalt Mixtures

Asphalt mixture is a typical elastic, sticky, plastic complex, within different temperature range, showing a different state.As a result its mechanical properties are not only affected by the external variables, but also its internal variables.The majority of Asphalt mixture are aggregates, the volume fraction of which is normally around 90% of the total volume of the mixture asphalt. The mechanical property of the asphalt mixture depends also upon the interlock of the particles characterized by the shape of the aggregates and the interaction between them used in the mixture.In view of this, the element of ellipsoidal shape is used in the coarse aggregates modelling in the paper.The model, including the geometric representation of ellipsoidal particles, the contact detection algorithm between particles or between particle and boundary, the determination of the contact point, the calculation of the magnitude of particle overlap, the search algorithm of neighbor particles, the packing method, and the solution of polynomial equation, is described in detail. The random packing program of aggregates based on the geometric potential algorithm is developed on the platform of VC++.The numerical model is applied to simulate the random packing of mono-sized and binary mixtures of ellipsoidal particles. Packing density and coordination number reflecting packing structure properties are used as important research indicators to analyze the effect of particle shape and boundary conditions on the packing structure of mono-sized particles, and discuss the effect of the volume fraction, relative size and geometric shape of particles on the packing structure of binary mixtures of particles. Simulation results show that:relative dimension of the boundary, ratio of particle equivalent radius to length of cubic container, has a significant influence on the packing density and coordination number, both of which increase with relative dimension of the boundary decreasing; The closer three-dimensional size is, the denser the packing of particles is; The trend of changes in packing density is consistent with that in average coordination number, both of which decrease with the aspect ratio increasing; For the binary mixtures of ellipsoidal particles, With the increase in the volume fraction of small-size particles, porosity of the binary mixtures decreases, but increases as the volume fraction increases to above 30%, during which, partial mean coordination number for the contact of small-size to small-size or large-size to small-size particles increases, but for the contact of small-size to large-size or large-size to large-size particles decreases; With the increase in the equivalent radius ratio of large-size to small-size particles, porosity of the binary mixtures gradually decreases, the mean coordination number of individual component for large-size particles increases, but for small-size particles has no major changes; The smaller the aspect ratio is, the denser the packing of binary mixtures is, and the larger the coordination number of individual component is.To verify the reliability of the numerical model, a laboratory test has been performed. Spherical cobble and ellipsoidal cobble are used for coarse aggregates. Influence of particle shape on VCADRC for skeleton structure is tested. The results show that:VCADRC formed by ellipsoidal cobble is obviously higher than VCADRC formed by spherical cobble; VCADRC formed by each single group of aggregates are higher than VCADRC formed by each grade of aggregates for both shapes; The combination of different particle shape would lead to the relative VCADRC value changes for the same grade distribution; Different grade distribution would lead to VCADRC value changes for the combination of same particle shape. From the above analysis, the results of numerical simulation agree well with the test data.