Voids and masonry behind finishing mortars detected by infrared thermography and ultrasonic measurements

Infrared thermography (IRT) and ultrasonic velocity (USV) measurements were combined in an experimental study to evaluate their effectiveness when detecting holes and type of masonry behind 15-mm thick finishing mortar. The voids were detected in three prototypes using IRT activated by solar radiation or artificial heat source; masonry was also approximately identified. USV semi-direct measurements gave lower values around the boles. However, differences in mortars' stiffness affect the results obtained in USV measurements, and this was confirmed by tests on samples made with the same mixtures of the finishing mortars