Hygroscopic behavior of zeolite lightened mortars contaminated with Na2SO4.

Masonry, rendering, and plastering mortars are during their lifetime impressed with many harmful factors that negatively affect their functional, technical, and durability parameters. Inorganic salt and water are considered as the most aggressive agents damaging mortars and other inbuilt structural materials. The excessive salt presence and high moisture content are typical especially for older buildings, where water-proof horizontal insulation is missing or in the case of accidents of water or sewage pipeline, flooding, improper restoration treatments, buildings usage, etc. Except salt crystallization, their hygroscopicity represents serious risk for material vulnerable to moisture induced damage. On this account, the analysis of hygroscopic behavior of non-hydrophobized mortars that should find use in masonry repair is the subject of the presented research. The examined mortars were produced from different type of binder: i) lime hydrate, ii) natural hydraulic lime, iii) lime-cement blend, and zeolite, which fully replaced silica sand in reference samples. The basic characterization of mortars was done by the assessment of their structural parameters, mechanical and thermal properties. Specific attention was paid to the analysis of water vapor storage capacity of mortars, which was done by the measurement of sorption and desorption isotherms. The use of zeolite enabled to produce highly porous mortars with sufficient mechanical strength and high sorption capacity for water vapor which can find use in passive control of indoor climate. According to IUPAC classification, the sorption/desorption isotherm were of type IV, i.e. with hysteresis loop and obvious capillary condensation. [ABSTRACT FROM AUTHOR]