Pore scale modelling of moisture transfer in building materials with the phase field method

Abstract

This study explores the applicability of the phase field method for modelling moisture storage and transport in porous materials. Accordingly, the system is treated as a continuum where the phases (liquid and humid air) are separated through a diffuse interface, which evolves in the pores until the equilibrium state is reached. The interface thickness is related to the surface tension, while the contact angle is defined as a boundary condition. The mass transfer in the porous matrix is driven by the Cahn-Hilliard equation and the phase transition is controlled by an equation of state. The above method is tested for a simple geometry (infinitely extended parallel plates), by comparing the numerical outcomes against available measured data and analytical solutions. The challenges arising for a further application to complex pore structures and real building materials are discussed.