A micromechanical model to evaluate the impact of air void content and connectivity in the oxidation of asphalt mixtures

• This paper presents a FE micromechanical model of oxidation in asphalt mixtures.
• The impact of the void phase on oxidative hardening of mixtures is evaluated.
• The model includes oxygen diffusion, chemical kinetics and mechanical simulations.
• Dynamic modulus was numerically computed in the first 5 years of pavement service.
• Air void content and connectivity strongly impact oxidative hardening in pavements.

Asphalt oxidation is a chemical reaction between asphalt binders and oxygen that causes irreversible changes in the properties of asphalt materials used in pavement structures. This paper explores the influence of the air void phase of asphalt mixtures on oxidation. Microstructures of an asphalt mixture with probable internal air void structures were generated and implemented in finite elements, and they were used in combination with oxygen diffusion and chemical kinetics models to estimate the changes generated in the mechanical properties of the material. The results confirm that the air void phase strongly impacts the stiffening processes caused by oxidation in asphalt mixtures.