Dissolution kinetics of trapped air in a spherical void: Modeling the long-term saturation of cementitious materials

The saturation of air-entrained cementitious materials governs their resistance to freeze-thaw cycles. Upon immersion in water, water is sucked in the capillary porosity and part of the air initially present is trapped. This trapped air slowly dissolves and diffuses outward, leading to a slowly increasing saturation. Building on efforts in fields ranging from gas-liquid interfaces to multi-phase transport and cement sciences, a model is derived to describe the governing physics behind the long-term saturation rate in immersed cementitious materials due to the dissolution and diffusion of trapped gaseous air in a spherical air void. We model how liquid water continuously enters a single air void and how various material properties influence the time to complete dissolution of air trapped in the spherical void. The relative influence of advection, diffusion, and various materials properties are studied and the model results are found to agree with imaging studies and theoretical models.