Effect of Presence of Salt on Hygric Performance of Ceramic Bricks

Abstract

The effect of presence of a salt on parameters of moisture transport and accumulation, namely water vapour sorption and dependence of water vapour permeability on moisture content is studied. The analysis is done for three types of commonly used burnt clay bricks with different hygroscopic ability. The experimental work consisted in determination of mineral composition, pore structure parameters, adsorption curves and water vapour permeability of the salt-free and saline specimens. The presence of salt resulted in a significant increase of the hygroscopic moisture content. In the case of practically non-hygroscopic ceramic bricks, the sorption measurement has confirmed the acceptable agreement with a simplified calculation, based on the assumption of independence of the moisture adsorption by salt and by material. A deviation from the calculation was observed at high relative humidity values, where the sorbed amount of moisture was lower than the calculated one. In case of the hygroscopic brick, an interaction between the hygroscopic moisture of the material and the moisture of the salt was also identified at lower relative humidity values. Salt presence had practically no influence on water vapour transport at higher moisture contents where the cumulated effect of the water vapour diffusion and the surface diffusion was present. On the other hand, at low moisture contents salt crust formation occurring during the dry cup measurements caused a noticeable decrease of the resultant water vapour flow.