Evaluating the aggregate structure in hot-mix asphalt using three-dimensional computer modeling and particle packing simulations

In a hot-mix asphalt (HMA) pavement, the aggregate structure serves as a backbone and is primarily respon- sible for resisting pavement distresses. A sound aggregate structure implies optimal packing of aggregates providing both particle-particle contact and sufficient void space to fill in asphalt. In this paper, three-dimensional particle pack- ing concepts are applied to the study of aggregate structure in HMA. A sequential deposition packing algorithm was used for packing typical aggregate gradations. The packing fraction and the distribution of particle-particle contacts in the simulated compact were studied. The packing simulation gave satisfactory results when aggregates above a certain minimum size were considered. Regression models were established to estimate the coordination number of any size aggregate in the compact. Such studies, in conjunction with the recent advances in X-ray computed tomography imag- ing techniques and discrete element modeling (DEM) simulations, have tremendous potential to help develop a deeper understanding of the HMA aggregate structure, develop and optimize the various parameters that describe the aggregate structure, and relate these parameters to the performance of pavements in a scientific way.

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