Introduction of a Single-Sided H-NMR System and its First Application to Non-Destructive Moisture Measurement in Brick Masonry Structures
In FY2025, the Center for Conservation Science introduced a single-sided H-NMR system. Moisture contained within porous materials can induce various deterioration phenomena, including physical damage caused by salt crystallization and freezing, deformation due to expansion and contraction, and biological degradation such as mold growth. Therefore, understanding the moisture condition within materials is a key factor in assessing deterioration risks and determining appropriate conservation strategies.
Single-sided H-NMR detects NMR signals from hydrogen nuclei in water by applying a magnetic field generated by the instrument. By analyzing the intensity and temporal variation of these signals, it is possible to evaluate both the moisture content and the mobility of hydrogen in water within the material.
In March 2026, an on-site investigation was conducted on a brick masonry building where deterioration of the wall surfaces had progressed due to salt crystallization associated with the capillary rise of seawater. This survey represents the first field application of the system since its introduction. Non-destructive measurements of moisture content profiles in the direction of depth were carried out. Conventional non-destructive methods are often limited to surface measurements or require smooth surfaces, making it difficult to obtain information about the internal condition of deteriorated walls. In contrast, this method enables the acquisition of depth-resolved moisture distribution profiles regardless of surface condition.
This study was conducted as part of a collaborative research project involving the Tokyo National Research Institute for Cultural Properties (TOBUNKEN), Kyoto University, Nagoya University, and the Nara National Research Institute for Cultural Properties (NABUNKEN), focusing on material treatments and environmental control strategies to mitigate salt weathering in brick masonry structures.
In the future, we aim not only to quantify moisture content but also to extend this technique to the non-destructive evaluation of material properties necessary for developing appropriate conservation measures. Furthermore, we plan to expand its application to a wider range of materials and cultural heritage objects.