Conservation studies of cultural heritage: X-ray imaging of dynamic processes in building materials

Abstract

High-resolution X-ray computed tomography (HRXCT) is a 3 D -imaging and analysis technique frequently used for the investigation of internal structures of a large variety of objects, including building materials. The 3 D information is important for the characterisation of internal dynamic processes ( e.g ., water and salt migration, the influence of temperature and/or relative humidity changes) in natural stone, mortars, bricks and concrete. One of the main advantages of HRXCT is the fact that it is a non-destructive characterization technique, which allows 3 D monitoring of internal structural changes at resolutions in the (sub)micrometre scale. Because of its non-destructive nature, it is possible to measure changes in porosity, evolution of micro-cracks, crystallization of salts and migration paths of liquids in the same rock sample over a specific time period. Driven by the technological and computational progress, the technique is continuously growing as an analysis tool in the Geosciences and is becoming an important method in the field of Cultural Heritage. In this manuscript, a short summary of the principle, the advantages and limitations of X-ray computed tomography are presented. In addition, an overview of some current applications of imaging dynamic processes (such as liquid migration, artificial stone weathering and treatment) is provided by means of HRXCT. This is demonstrated in studies related to conservation of Cultural Heritage.