Optimization of aggregates skeleton using laser-scanning technology and discrete element method

The skeleton of aggregates has a significant effect on the performance of porous asphalt mixtures. In this study, laser-scanning technology was utilized to obtain two-dimensional digital images of four groups of aggregates with different particle sizes. Digital image processing technology was used to obtain the basic dimensional indices such as area, perimeter, and equivalent ellipse of aggregate particles. Based on these indices, the morphological characteristics of the aggregates, including aspect, roundness, and angularity, were evaluated. Then, virtual uniaxial penetration tests were simulated via the discrete element method (DEM) and verified by the results of laboratory uniaxial penetration tests. On this basis, the visualization design of the optimal main skeleton for the porous asphalt mixture was conducted. Results show that the shapes of the aggregates were close to cubes. Aggregates with sizes greater than 4.75 mm had a more significant structural effect on the skeleton than those with sizes smaller than 2.36 mm. Coarse aggregates could form a stable skeleton by interlocking with each other, whereas the skeleton formed by fine aggregates was fragile. Coarse aggregates primarily withstood the external load while fine aggregates primarily limited the displacement of coarse aggregates. The optimal main skeleton designed by combining the DEM with the laser-scanning technology can provide new possibilities for the gradation design of porous asphalt mixtures.