Assessment of the influence of moisture content in enclosing concrete structures on heat losses

The purpose of the study is to determine the effect of wetting of internal surfaces of enclosing concrete structures on heat losses. Based on the experimental data earlier received by the authors, the increase in the value of heat losses under different conditions has been proved. The irreversible character of wetting of concrete in operating conditions at increased humidity has been experimentally proved. The multi-layer model of large-panel residential buildings and the theory of heat conduction at a constant value of the coefficient of heat conductivity inside the layer have been used in the studies. M250 concrete samples made by different manufacturers were chosen as the basic material for the research. Wetting was carried out in laboratory conditions, in a humid environment with a relative humidity of 100% with partial immersion in water at atmospheric pressure and temperature of 200C. The flux through each layer of a given thickness was estimated according to the Fourier law. According to the results of theoretical and experimental research, it was found that: the time of drying of concrete exceeds wetting time more than twice, therefore wetting process in conditions of ineffective ventilation becomes irreversible; when wetting only the internal layer of the building envelope increases heat losses by about 5%, and wetting of internal layer leads to wetting of intermediate layer of building envelope and increase heat losses by 25%.