Hygric properties of porous building materials (Ⅳ): Semi-permeable membrane and psychrometer methods for measuring moisture storage curves

摘要

The moisture storage curve is an important hygric property of porous building materials. It describes the moisture storage characteristic of a material via the relation between the moisture content and the moisture potential. Current experimental protocols for measuring moisture storage curves are not satisfactory, as they often require extensive facilities while still lacking the capability to handle the adsorption process in most of the over-hygroscopic range. This paper proposes two novel and simple methods - the semi-permeable membrane method and the psychrometer method - to solve these issues. Measurements on calcium silicate, autoclaved aerated concrete and ceramic brick are performed and validated by comparing the experimental outcomes obtained from these two novel methods and from other existing protocols. It is proven that the semi-permeable membrane method and the psychrometer method are applicable for both adsorption and desorption processes, the latter both from saturated and capillary moisture content. Limited by the accuracy of the psychrometer and the condensation caused by temperature fluctuations, these two methods show their best applicable range for capillary pressures below -1.10(5) Pa. The semi-permeable membrane method and the psychrometer method also feature in low cost, simple handling and application efficiency.