Measurement of the content of unfrozen water in cellular glass at low temperatures
Relevance of the work is due to the active use of cellular glass as a heater in construction and, as a consequence, the requirement to study its physical properties over a wide temperature range. Methods of research. The determination of the amount of water in the liquid state in cellular glass at negative temperatures was performed with the microwave water content measurements. This method is based on measuring the power of electromagnetic radiation in the microwave range that has passed through the cellular glass sample under study when its temperature changes. The measurements were performed at a frequency of 10 GHz. Purpose of the work: to study the possibilities of the method for determining the amount of moisture in cellular glass at the temperature range 0... -100 ° C. Results. Experimental data are given on the measurement of the amount of unfrozen water in fine-pored cellular glass as a function of temperature. Water in a supercooled state has a number of anomalous properties, which should be taken into account when using humidified media at negative temperatures. When calculating the amount of water in a sample, it is necessary to take into account the real and imaginary parts of the relative complex permittivity of supercooled water at the microwave range. The authors have used the empirical dependence of the electromagnetic parameters of water at negative temperatures when calculating the amount of supercooled water in fine-pored foam glass; it was proposed by the co-author of this paper, O. Orlov. As a result of the experiment it was shown that some of the water in the material under study remains in the liquid state to a temperature of -80 ° C. Conclusion. It is established that the major part of the liquid water in coarse-porous cellular glass transforms into a solid phase - ice at a temperature close to 0 °C; in the fine-pored cellular glass, this transition extends to -30 ° C. Moreover, in the cooling-heating cycle of cellular glass, a hysteresis of electromagnetic losses was revealed. The proposed method for determining supercooled water will be useful to civil engineers when calculating buildings and structures using cellular glass as a heat insulation material.