Monitoring water transfers in limestone building materials with water retention curve and Ground Penetrating Radar: A comparative study

The rehabilitation of older buildings is necessary to achieve both a reduction in energy consumption and the preservation of cultural heritage. To ensure a successful building rehabilitation project, an efficient diagnosis makes it possible to determine the various existing pathologies and their causes. In this study, we focus on the “Tuffeau”, which is a kind of limestone widely found in older buildings of the Loire Valley region in France. The durability is strongly affected by the water content for such kind of material. However, very few studies can be found in this field. Moisture condition measurements are currently carried out using punctual sensors placed into the walls. These sensors record highly localized measurements through structural alteration (coring). This paper proposes two non-destructive testing (NDT) methods with the application of Ground Penetrating Radar (GPR) in order to compare the ability of the two methods to analyze the water transfer in limestone blocks. A modified water retention curve model is proposed here to characterize the water gradients in limestone blocks: the limestone - water characteristic (LWC) model. The analysis of the results shows good agreement between the two GPR methods, which shows good capability of monitoring water ingress linking to the results of LWC model.