Non-invasive moisture measurements after flooding simulation of stone and brick masonry full-scale models: effectiveness of GPR

A high frequency GPR system was used to perform static measurements on selected points of the small houses at selected intervals during the drying period. The results were compared with the reference measurements taken before the two flooding simulations. The observation period for GPR experiments was extended along a couple of months. Different measurement methodologies and different procedures for signal analysis were tested in order to find the most effective way to use this equipment. Radar velocity, radar amplitude in transmission and in reflection mode, radar wave distortion and spectra were analyzed vs. time after flooding and were compared with moisture levels assessed with the powder drilling method. Radar velocity measurements were found meaningful and consistent with the expected drying process and with the powder drilling results. On stone masonry houses, the radar velocities were also indicative of different indoor vs. outdoor moisture evolution. A correlation between the radar wave distortion and the moisture level was observed on the brick masonry houses. Simulations were performed to define which frequencies and TX-RX separations would be needed to assess with this method also the lower moisture levels measured on the less porous stone masonry. Radar amplitudes do not seem to be promising and competitive with the other radar parameters to the purpose of moisture assessment.