A computational-experimental method to determine the effective diffusivity of asphalt concrete

This study utilizes a computational-experimental method to determine the effective oxygen diffusivity of asphalt concrete based on diffusivities of its constituents, i.e., air void, aggregate, and asphalt binder phases. The proposed method enables the estimation of oxygen diffusivity of asphalt concrete, which is very challenging, if not impossible, to determine experimentally, and addresses various controversial factors, such as consideration of accurate microstructures, high contrast in properties of constituents, and high volume fraction of aggregates. Random particle generation algorithm and X-ray computed tomography techniques are used to reconstruct realistic microstructural representation of asphalt concrete materials. Then, finite-element (FE) diffusion simulations are used and the results are compared with closed-form solutions to estimate the effective oxygen diffusivity. Capabilities of the proposed method are illustrated by comparing the simulation results with relevant analytical solutions, rigorous bounds, and available experimental measurements regarding oxygen diffusivity of fine aggregate matrix (FAM) of asphalt concrete. Finally, the proposed technique is used to simulate two-dimensional oxygen diffusion problem in a dense-graded asphalt concrete.