Abstract
The thermal and moisture properties of building envelope materials determine their performance over many years of use. Moisture has a particularly negative impact, impairing all the technical parameters and adversely affecting the microclimatic conditions inside the building. This article presents research and analysis on the moisture behavior of partitions made of autoclaved aerated concrete. Autoclaved aerated concrete is a very popular material for building external walls because of its relatively good thermal insulation and sufficient strength, if it is not subjected to increased moisture. This study investigated how the moisture content of this material changes with the change in relative air humidity. The four most popular density classes were studied. The sorption isotherms were determined by the static gravimetric method throughout the whole hygroscopic range. Moreover, the applicability of various models to describe sorption isotherms of this material group has been extensively evaluated. The tested models (Peleg, Redlich, Chen, Oswin, Henderson, Lewicki, Caurie, and GAB) all provided a very good fit with the experimental results for the tested material group (R2 ranged from 0.9599 to 0.9978). This paper indicates that the use of two additional approximation parameters (SSE and RMSE) allows a more precise assessment of the quality of individual models.
Highlights
The properties of a building envelope made of hygroscopic materials strongly depend on the moisture content—with an increase in moisture, the thermal insulation performance of the partitions decreases, and both the quality of the indoor climate and the durability deteriorate
The shape of the measured isotherms corresponded to a type III isotherm in the Brunauer and International Union of Pure and Applied Chemistry (IUPAC) classifications
Based on moisture sorption studies, this process was found to proceed with similar intensities in four classes of tested aerated concretes
Summary
The properties of a building envelope made of hygroscopic materials strongly depend on the moisture content—with an increase in moisture, the thermal insulation performance of the partitions decreases (increased energy loss), and both the quality of the indoor climate (mold growth, increased VOC emissions) and the durability (physical, chemical, and biological damage) deteriorate. Significant attention has been paid to problems associated with the dampness of building materials, and in particular to the research and modeling of sorption isotherms. Sorption isotherms describe the adsorption properties of a porous material. The shape of a sorption isotherm depends on the adsorbent microstructure (in particular, the pore size) as well as adsorbate–adsorbent interactions; different hygroscopic materials exhibit very different sorption isotherm characteristics.
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