Application of instantaneous profile measurement of moisture content and moisture potential in porous materials

摘要

Due to limits in current moisture content and moisture potential measurement technology, moisture transport is normally investigated under equilibrium conditions. Most processes we observe in nature are, however, transient and hardly ever reach an equilibrium stage. This means that future experimental methods in moisture transport investigation will focus on transient processes. One such method is the instantaneous profile measurement (IPM) technique frequently used in soil science. It can be applied to investigate moisture transport under transient conditions. Two measurement principles are combined in one material to record data for moisture content and moisture potential at the same time and at various points. As output, moisture content and moisture potential profiles are plotted against space and time. The method was applied to different porous materials, and hygroscopic loading and deloading cycles were conducted in the relative humidity range between 30 and 97%. The data obtained is not in strict agreement with static or steady-state observations. This reveals information about moisture transport kinetics. These findings are discussed in the context of the literature and with regard to their significance for current moisture transport models, which are typically based on equilibrium data.