Analysis of dielectric mixing models for the moisture assessment of porous building materials

Abstract

The moisture content in materials has influence on their thermal, acoustic and mechanical properties, what has clear relation to their durability and service life. On this account, there is necessary to monitor liquid moisture content in building materials, and to know its influence on their behavior and performance. This information can find use already in the design of building structures as well in the restoration and reconstruction of existing buildings.In the presented paper, the problem of calibration of high frequency time domain reflectometry (TDR) method for moisture content measurement in porous building materials is studied. In this work there is focused on analysis of dielectric mixing models that can be used for calibration of dielectric moisture measurement methods. Experimentally accessed data were compared with the results of several mixing dielectric models like formulas developed by de Loor, Dobson, Polder and van Santen and Lichtenecker as well as Wiener’s and Hashin-Shtrikman’s bounds, which define a theoretical minimal and maximal value of permittivity for the given moisture content.On the basis of performed experiments and calculations, the suitable mixing models are identified and recommendations for their practical application are formulated.