Micromechanical Study of Porosity Effects on Coupled Moisture-Mechanical Responses of Viscoelastic Asphalt Concrete

The present paper offers a micromechanical modeling approach to evaluate the impact of the porosity structure on the response of asphalt concrete as a viscoelastic multiphase material under the combined action of moisture diffusion and mechanical loading. Moisture infiltrates and degrades asphalt concrete material properties and encourages the fast propagation of cracks upon additional mechanical loading. The critical impacts of the porosity structure on the coupled moisture-mechanical responses of asphalt concrete have been highlighted by both experimental and numerical studies. It is therefore imperative to develop a clear understanding of the various impacts that the porosity has on the overall performance of this viscoelastic composite. In this work, a micromechanical modeling approach is used in combination with a methodology to randomly generate realistic pore properties within an asphalt concrete specimen. The relevant effects of the porosity structure are assessed for two sets of moisture diffusion coefficients representing low-end and high-end diffusivities for the aggregates and matrix. Finite-element models are developed using coupled nonlinear viscoelastic-moisture damage-mechanical damage constitutive relationships. The effects of varying the pore content, shape, and size distribution on the stress distribution and damage evolution within asphalt concrete specimens are assessed. A numerical approach is also presented to estimate the effective moisture diffusivity of asphalt concrete as a function of the pore shape and content. The outcome sheds light on our understanding of how the porosity structure of asphalt concrete affects its moisture-mechanical responses. (C) 2021 American Society of Civil Engineers.