A sorption isotherm is the relationship between the moisture content in a material and the relative humidity of the surrounding atmosphere in an equilibrium situation. Most often, the sorption isotherm is measured with a gravitational method. This work presents a method to measure the adsorption isotherm of a porous construction material (sand-lime) with a hygroscopic method. The set-up of the experiment consists of a glass vessel that contains a humidity and temperature sensor. The measurement starts with drying a sample completely inside the vessel by blowing dry air through the vessel. After injecting a known amount of water into the vessel, the water evaporates and is adsorbed partly by the sample until an equilibrium state is reached. With the known amount of the injected water, the measured humidity inside the vessel and the volume of the vessel, one point of the adsorption isotherm is determined. For measuring the next point, more water is injected into the vessel. The desorption isotherm can also be measured with this technique.
|Title of host publication||1st International Conference on the Chemistry of Construction Materials, 7-8 October 2013, Berlin|
|Editors||D. Stephan, H. Daake, von, V. Markl, G. Land|
|Place of Publication||Berlin|
|Publisher||GDCh Division of Chemistry of Construction Chemicals|
|Publication status||Published - 2013|