Electrical Impedance Used for Measurement of Moisture Distribution in Thermal Insulation Plasters

Abstract

High moisture in building materials has a negative influence on their physical and thermal insulating properties. When building materials incorporated in a structure exceed the maximum permissible moisture, the material could change its properties to such an extent that its next usage is unfeasible. In case of thermal insulating materials, it causes serious degradation of thermal insulating properties. During the development of advanced thermal insulation plasters, long-term laboratory experiments were performed using masonry construction fragments, which focused on the study of their moisture proportions. For this purpose a new non-destructive method of electrical impedance was used, which enables measurements on defined levels in a matrix of test samples. Results obtained by measurements made on the surface of the samples were compared with the results obtained by a capacitive hygrometer. It was concluded that these methods provided similar results. The least moisture sensitive was the mixture, which was applied on masonry pillar E. In comparison with used thermal insulation plasters commonly used today this plaster shows considerably lower value of mass moisture under laboratory conditions, 1.38%. This pillar also exhibited the most uniform course of conductance measured along its height.