The assessment of mechanical properties of thermally stressed composite materials using radio frequency electrical field

The assessment of mechanical properties of thermally stressed composite materials using radio frequency electrical field

en

The main topic of this paper is the testing of cement-based composite materials that were stressed by high temperature. Impedance spectroscopy has been used as a non-destructive measurement method. The specimens were made from mortar mixture of CEM I type Portland cement, silica sand and fine gravel of various size classes for two sets of specimens. The sets, A and B, differed from each other also by the plasticizer used. The specimens were exposed to high temperatures in the range 23–1200°C. Studying the structural changes in the process of heat build-up is an efficient way to assess the reliability of whole construction. Using the impedance spectra the relative permittivity, electrical conductivity and other characteristics have been obtained. In accordance with Debye‘s theory of dielectrics the changes of impedance parameters have been put into context with structural changes. For higher range of frequencies, 100 MHz up to 3 GHz, R&S ZNC vector analyzer with DAK 12 coaxial probe manufactured by Speag has been used. In this frequency spectrum the electrical conductivity and relative permittivity as a function of frequency have been measured.

The main topic of this paper is the testing of cement-based composite materials that were stressed by high temperature. Impedance spectroscopy has been used as a non-destructive measurement method. The specimens were made from mortar mixture of CEM I type Portland cement, silica sand and fine gravel of various size classes for two sets of specimens. The sets, A and B, differed from each other also by the plasticizer used. The specimens were exposed to high temperatures in the range 23–1200°C. Studying the structural changes in the process of heat build-up is an efficient way to assess the reliability of whole construction. Using the impedance spectra the relative permittivity, electrical conductivity and other characteristics have been obtained. In accordance with Debye‘s theory of dielectrics the changes of impedance parameters have been put into context with structural changes. For higher range of frequencies, 100 MHz up to 3 GHz, R&S ZNC vector analyzer with DAK 12 coaxial probe manufactured by Speag has been used. In this frequency spectrum the electrical conductivity and relative permittivity as a function of frequency have been measured.