GPR-Based Characterization of Multi-Leaf Historic Masonry: Layer Detection and Moisture-Induced Signal Attenuation in a 11th-Century Church

While visual inspections can contribute to understanding the current state of the historical structure, investigating the internal masonry composition is necessary for a comprehensive structural assessment. In this context, non-destructive testing (NDT) plays a crucial role in the investigation of built heritage, as it can provide rapid, efficient, and precise diagnostics of historic masonry. Ground Penetrating Radar (GPR) has emerged as one of the most suitable non-invasive methods for analyzing historical structures in recent decades, particularly due to its ability to provide real-time data with a high degree of accuracy, without compromising the integrity of the building. Aiming to support the characterization of historic multi-leaf stone masonry using GPR, tests were carried out on different masonry segments of the Church of San Frediano, in Pisa, Italy. The investigation aimed to identify recurring electromagnetic wave reflection patterns associated with different internal masonry configurations, embedded elements, and variations in signal attenuation. The results demonstrated that GPR is an effective tool for identifying internal layers and hidden elements. Pronounced signal attenuation observed particularly in the lower portions of some masonry sections reduced the resolution and hindered radargram interpretation.