An improved model incorporating Pitzer’s equations for calculation of thermodynamic properties of pore solutions implemented into an efficient program code

Salts in porous building materials are not only considered as a major cause of damage but also strongly affect the hygric and capillary transport properties of such materials. This paper describes a model implemented into an efficient computer code that can be used for predicting the non-ideal behavior of pore solutions of complex composition. The model is based on the Pitzer ion interaction approach. Model parameters are provided and validated for the system Na+–K+–Cl-–NO3-–SO42-–H2O in the temperature range relevant to most buildings, i.e. from the temperature of freezing to 45 °C. This offers a number of potential applications including the incorporation in chemical equilibrium and humidity and moisture transport models.