Multi-disciplinary characterisation of a sandstone surface crust.

Sandstones are used in many contemporary and historical buildings. With time, these buildings become dark and a surface crust is formed. Generally, these crusts mainly consist of minerals of which the constituents were mobilised from the interior of the stone, and material from the surrounding environment like air pollutants and dust. Many traditional techniques, such as optical microscopy, Scanning Electron Microscopy and the Drilling Resistance Measurement System, have been used to study these crusts in the past. The advent of more advanced techniques allows a better characterisation of sandstone surface crusts, commonly present in urban stone decay. High-resolution X-ray radiography and tomography, micro X-ray absorption spectroscopy (micro-XANES) and 2D micro-XRF scanning at laboratory and synchrotron sources, combined with more traditional research methods were applied to the study of a sandstone surface crust. This shows that the combination of these highly advanced techniques, which were not designed with the purpose of answering geological or environmental questions, can generate complementary 2D and 3D imagery of geological materials, opening up new approaches in the study of element migration inside porous geomaterials. CAPSULE: I hereby state that this work is significant to the rest of the scientific community.