Application Instructions
32
Hydromette BL Compact RH-T
4.4 Sorption Isotherms
Sorption isotherms describe the equilibrium state of the sorption of
a material on a surface at a constant temperature. In this
equilibrium state, the relationship between water content and
equilibrium moisture content of the surface (i.e. of the material) can
be described and represented by a curve. Each moisture value can
be allocated to an appropriate water content of the material using
this curve.
Different materials also have different sorption behaviour
depending on the specific properties of the material.
As these processes are extremely complex, the sorption curves are
obtained empirically, i.e. they relate to practical data and
experience. For each material, its own characteristic curve must be
obtained experimentally.
Measuring the relative air humidity/water activity in building
materials
This method is mainly used for measurements at depth in old
building structures where measurements using the resistance
measuring method (sandstone, quarry stone, damp walls with
blooming, etc.) do not provide reproducible results. For this, the
Blue Line Compact RH-T devices with tube lengths of 160 and 350
mm are available. For measurements over a long period at multiple
points or at different depths, drilled holes should be se cured and
closed.
The method for measuring the relative air humidity/equilibrium
moisture content in screeds has been used for a long time in Great
Britain and the Scandinavian countries. Compared to the non -
destructive measurement or the resistance measurement, it is,
however, more time-consuming and requires suitable drilled holes.
However, it provides very reliable results when an equilibrium
moisture content is sought. This method also increases the
