Modelling of salt crystallization in building materials with microstructure

Modelling of salt crystallization in building materials with microstructure – Poromechanical approach

Koniorczyk, Marcin / Gawin, Dariusz

Highlights ► The influence of pore micro-structure on the salt transport and crystallization is investigated. ► FEM and FDM are used to solve the governing equations. ► The effective stress principle is applied to account for the crystallization pressure. ► The equation defining solid surface fraction in contact with the salt crystal is derived. ► The fine micro-structure reduces the development of the crystallization pressure.

Abstract A novel mathematical model of chemo-hydro-thermo-mechanical behavior of porous building materials considering salt transport and crystallization is presented in the paper. The additional pressure, which is generated during the salt crystallization, is taken into account by means of the effective stress principle. The solid surface fraction in contact with the growing crystal is calculated based on the pore distribution model obtained by mercury intrusion porosimetry. The Pitzer ion interaction model and the Freundlich non-equilibrium isotherms are utilized to define the kinetics of salt crystallization/dissolution. The properties of the solution and the magnitude of crystallization pressure depends on the internal pore structure of the material. The model equations are solved by means of the finite element and finite difference method. Some test problems, as well as the drying examples of brick and concrete wall saturated with the NaCl solution, are presented.