For several decades, rutting in asphalt pavements has not been fully addressed or prevented. Study on the microstructure of asphalt concrete may provide a good alternative way to approach a solution. Conventional microstructure modeling based on computed tomography (CT), however, is expensive, time consuming, and specimen destructive. In this paper we present a study on discrete element modeling of asphalt concrete in which the microstructure is described based on the compositional phases. This approach is less expensive, more rapid, nondestructive, and easier to use relative to the CT approach. First, a new algorithm for generating coarse aggregate elements with irregular shapes is developed. It considers the shape and orientation distribution of particles in the microstructure of asphalt concrete. The irregular shapes are created based on the mechanism of sieving analysis. The random distribution of orientations is modeled with a rotation algorithm. Some particular problems such as the issue of “floaters” are solved with an iteration method in the proposed algorithm. Second, the air void phase, which is treated as the second microstructure component of asphalt concrete, is established with a regression model based on data measured from specimens fabricated with a Superpave gyratory compactor. Finally, the developed microstructural model of asphalt concrete is validated with volume fractions of phases in actual asphalt mixture specimens. The results are quite satisfactory.
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