HYSTERESIS AND TEMPERATURE DEPENDENCY OF WATER VAPOR SORPTION

Moisture in porous building materials plays an important role in almost all durability problems. The sorption characteristics of building materials exhibit hysteresis in the way the equilibrium curves develop between adsorption and desorption. The sorption curves are also somewhat temperature-dependent. These facts are most often neglected in models for combined heat and moisture transport in materials. This study provides the sorption isotherm and its hysteresis of different porous building materials. The paper seeks to contribute to the knowledge base about such sorption characteristic by presenting some new measurements of hysteresis and temperature dependency of the moisture sorption characteristics of different porous building materials: concrete, porous concrete, cement plaster, limes cement plaster, brick, and spruce. Scanning curves are measured for all materials where periods with adsorption and desorption interrupt each other intermittently between 0% and 97% of relative humidity.