Infrared thermography (IRT) was used to map
moisture distribution and to identify areas with
anomalous water content in modern and ancient
building structures. This paper describes two
different approaches that used IRT to map evaporative
flux on wall surfaces, and to assess the potentials
and limits of the technique. The first part of
the paper describes a set of laboratory measurements
to evaluate water diffusion inside the wall,
as well as evaporation rate versus moisture
content. Measurements of evaporative flux on
laboratory samples provided an empirical relationship
between evaporative flux and cooling under
specific conditions inside mesopores and micropores
allowing the typical trend of the evaporation
rate to serve as a key for reading thermographic
surveys to identify areas at greatest risk of surface
degradation. Capillary rise (water rising from soil
due to capillary of porous materials) was also
evaluated under laboratory-controlled conditions.
In addition, active and passive tests were applied
in-situ to map different areas on the building
surface according to water evaporation. The output
was not the absolute moisture content, but rather
a value ranked according to a scale on which the
saturated condition represented the minimum
negative value and zero represented the physical
moisture content (dry). This map was coupled with
the surface temperature as given by the natural
evaporation when equilibrium conditions with the
environment were reached, as in the passive
approach. This was obtained by processing the
experimental data using a robust algorithm that
synthesized the surface temperature history during
the test with enhanced evaporation. Finally,
outputs of the processing algorithms were overlapped
with the visible image and put in the same
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