Modified pressure plate method for measuring adsorption moisture retention curves

Abstract

The pressure plate is one of the most widely used methods to measure the moisture retention curves of porous materials in the over-hygroscopic range. Due to its working principle and operational protocol, the traditional pressure plate method is only applicable to the desorption process. In this study, we propose a novel method to measure the moisture retention curves for the adsorption process. Only simple modifications to the traditional pressure plate setup are needed, and minor changes in the experimental procedures are required. Validation measurements are performed on three representative porous building materials: calcium silicate, autoclaved aerated concrete and ceramic brick. Results from the modified pressure plate method are compared with those from the semi-permeable membrane and the psychrometer methods. The modified pressure plate method successfully provides similar results to the other two established methods for all three materials, and hence proves to be reliable in determining the adsorption moisture retention curves in the over-hygroscopic range.