Moisture Transport in Salt Free and Salt Contaminated Ceramic Bricks

AbstractIn this work the effect of salt contamination on moisture transport parameters - the water vapor permeability and moisture diffusivity is studied for case of ceramic bricks with very low and low hygroscopic ability. The analysis is focused to small salt concentrations, having practically negligible effect on the material porosity but significantly increasing hygroscopic moisture content of the bricks.The simply experiment, consisting in monitoring of isothermal one-dimensional capillary uptake and following drying was carried out for salt free and salt contaminated bricks. Tests were done for two different salt concentrations. The moisture uptake and release during the tests was determined by weighting the samples. The experimental results were compared with numerical simulation of the process of drying. In the simulations, desorption curves, measured from capillary moisture content were used as moisture storage functions. Within the hygroscopic range, moisture transport was specified by water vapor permeability, determined from standard cup measurements. Beyond the hygroscopic range, moisture diffusivity function, obtained from absorption coefficient for water and capillary saturation water content, was used for simulation of moisture transport.On the basis of the comparison, the effect of salt contamination on moisture transport parameters was evaluated. The presence of salt significantly lowered the water vapor permeability by the salt crust formation on the drying surfaces. However, the actual crust formation differed on the particular surfaces and was dependent on the initial moisture content at the surface as well as on the surface roughness