Gas Diffusion in Cement Pastes: An Analysis using a Fluctuating Diffusivity Model

TL;DR

This paper introduces a fluctuating diffusivity model to analyze gas diffusion in cement pastes, revealing non-Gaussian behavior due to microstructural heterogeneity, which impacts durability assessments of concrete.

Contribution

It applies a two-state fluctuating diffusivity model to describe oxygen diffusion in cement pastes, capturing non-Gaussian diffusion characteristics.

Findings

The model accurately describes oxygen diffusion coefficients.

Non-Gaussian diffusion with heavy tails observed.

Heterogeneous microstructure influences diffusion behavior.

Abstract

This work propose an application of the concept of fluctuating diffusivity to the diffusion of gas molecules in cementitious materials, particularly through a two-state fluctuating diffusivity (2SFD) model. The 2SFD model is utilized to investigate the diffusion of oxygen in cement pastes. The analysis provides a reasonable description of the diffusion coefficient of oxygen in cement pastes, and highlights the presence of non-Gaussian diffusion, which can be attributed to the heterogeneous microstructure. The presence of non-Gaussianity in the probability density of the molecule's displacement, characterized by heavier tails than those of the Gaussian distribution, may have a significant impact on the durability assessments of concrete structures.