Influence of temperature on crystallisation and dissolution of salts and salt mixtures in built environment

Abstract Salt weathering significantly degrades building materials, necessitating a thorough understanding of influencing factors. While prior research has focused on relative humidity (RH), temperature effects on salt crystallisation and dissolution remain less explored. This study examines selected single salts and mixtures, using the ECOS/RUSALT thermodynamic model to assess equilibrium behaviour across temperatures from 1 °C to 50 °C and RH values from 15% to 98%. Results show that crystallisation and dissolution RH generally decrease with rising temperature. Single salts exhibit monotonic changes, whereas mixtures behave variably. Calcium-rich mixtures have lower mutual crystallisation and dissolution RH than sulfate-rich ones, with further reductions in magnesium-containing mixtures. Lower temperatures promote the formation of more output salts. Model limitations are acknowledged to explain discrepancies between predictions and real-world observations. These findings enhance understanding of salt behaviour under climatic variations, aiding strategies to mitigate salt damage in building materials.