Method for Quantitative Assessment of Moisture Content of Porous Building Materials Based on Measurement of Thermal Inertia with Active Infrared Thermography

The presence of moisture in masonry is crucial because it causes and exacerbates various deterioration mechanisms, such as crystallization of salts, mechanical stresses due to freeze–thaw cycles, biological degradation, etc. The assessment of the water content is critical for cultural heritage buildings; thus, on-site non-invasive techniques have been proposed over time. An innovative active thermographic procedure is proposed and tested in a laboratory to assess the amount of moisture via a non-destructive approach. The methodology is based on heating a brick specimen together with a reference sample which has known thermophysical properties. Evaporation is inhibited by an impermeable film applied to the samples. The trends in the surface temperatures of both materials are recorded using infrared thermography and compared with each other: the calculation of the thermal inertia of the wetted material is retrieved from the comparison of the temperature trends in both samples. The water content value is thus determined from the thermal inertia of the sample.