Moisture content of natural stone: static and dynamic equilibrium with atmospheric humidity

Among hygric properties of stone material, the sorption behaviour is of essential importance because of the permanence of the processes involved. New results from static sorption experiments performed by standard techniques and by a new tool are reported for six different building stones. Furthermore, an example of dynamic sorption behaviour under continuously changing humidity is presented. For the static equilibrium sorption measurements a close relation to the stone type, its pore properties, such as specific inner surface, pore volume, pore size distribution as well as capillary water uptake and water saturation, is drawn. The comparison of the different data allows us to retrieve correlations between material features that are crucial for weathering processes. The sorption-desorption processes respond spontaneously on even small humidity changes as shown by the dynamic sorption experiment. A permanent 'breathing'-process of the material is imposed.