Equilibrium relative humidity method used to determine the sorption isotherm of autoclaved aerated concrete

The sorption isotherm of porous building material is basic information needed for the design and maintenance of materials. The equilibrium moisture content (EMC) method is used to determine this physical property. In this study, the equilibrium relative humidity (ERH) method was used to determine the adsorption data for autoclaved aerated concrete at seven temperatures and found that the ERH method could be used to determine the sorption data within a short time. Comparing with previous published data, no significant difference could be found at humidity >20%. Two different sizes of samples (small and large) revealed the same EMC data throughout the whole relative humidity (RH) range. The Oswin equation was the best ERH model for adsorption isotherm data. A temperature term could be incorporated into model for the adsorption data. Sorption isotherm data for other building materials could be determined with the ERH method.