2024 Volume 52 Issue 2 Pages 83-89
The diffusion of lightweight molecules in cementitious materials is an extremely important phenomenon, as it determines the lifetime and long-term reliability of structures made from cement-based materials, including reinforced concrete structures. Conventionally, the field in cement and concrete has employed a diffusion equation with an effective constant diffusion coefficient to predict the dynamics of the molecule, although this approach cannot treat non-Gaussian diffusion. Recently, the authors initially applied the framework of the fluctuating diffusivity, which can describe the non-Gaussian diffusion in heterogeneous nature, to the diffusion of oxygen molecules in dry cement pastes [Nakai and Ishida, Construction and Building Materials, 407, 133411, 2023]. In addition to oxygen molecules, low molecular gases such as hydrogen, nitrogen, and helium have traditionally been collected as benchmark data for discussing diffusivity in cementitious materials. This paper discusses the non-Gaussian nature of hydrogen and oxygen molecules diffusing in dry cement pastes.
