Laminar flow behavior of water through microscale pores of cementitious materials simulated by molecular dynamics method

The non-equilibrium molecular dynamics simulations were employed to study the transport process of water molecules through nanopores formed by cementitious minerals or their hydration products. The effects of pore size, pressure gradient, mineral type, and temperature on the dynamic properties of water flow were systematically examined and interpreted under the laminar flow conditions. The simulation results indicate that the flow behaviour of water molecules is influenced by the size of the pores. The shear viscosity of water is governed by the ratio between the thickness of the adsorbed water film and the pore size. Considering the variation of the self-diffusion coefficient of water molecules in micropores with pore size, it is possible to accurately calculate the permeability coefficients under different pore sizes. As the pressure gradient increases, the water flow characteristics in the microscopic pores are different from those in the macroscopic pores. Specifically, the shear viscosity decreases linearly, resulting in a linear increase of permeability coefficient. The type of mineral exerts a negligible influence on the flow characteristics of water molecules. Within the temperature range studied, both shear viscosity and dynamic viscosity decrease linearly with increasing temperature, while the permeability coefficient exhibits a linear positive correlation with temperature.