Monitoring of weathering and conservation of building materials through non-destructive X-ray computed microtomography

X-ray computed microtomography (μCT) is a promising non-destructive imaging technique based on measurements of the attenuation of X-rays. It provides information on the internal structure of small samples with a maximum resolution of 10 μm. For this study, two porous local natural building stones, the sandstone of Bray and the limestone of Maastricht, were selected. Possible applications of the μCT-technique for qualitative monitoring of changes comprise (1) to non-destructively determine porosity based on 3-D images, (2) to visualise weathering phenomena at the micron-scale, (3) to understand the rationale of weathering processes, (4) to visualise the presence of water repellents and consolidation products, (5) to monitor their protective effects during decay in order to understand the operating mechanisms and (6) to provide advise on the suitability of products for the treatment of a particular rock type. The μCT-technique proves to be a powerful monitoring tool for the future as the combination of 3-D visualisation and 3-D data provide new insights that could optimise conservation and restoration techniques of building materials.