CHARACTERIZATION WITH X-RAYS OF LIQUID LOCATION AND MIGRATION INSIDE BUILDING MATERIALS

Liquid migration inside building materials is influenced by the microstructure of the porous medium and by the physical characteristics of the solids and the fluids that occupy its pore space. Understanding the relationship between microstructure and transport is of great theoretical and practical interest since this has an influence on the macroscopical behaviour of a building material. Highly advanced imaging techniques like high-resolution X-ray Computed Tomography (HRXCT) and scanning micro X-ray Fluorescence (µ-XRF) were originally not designed to answer geological questions, but can actually generate imagery of geological materials at a micron scale. These new approaches enable to monitor liquids inside porous materials in a rapid, non-destructive, two- and three-dimensional way. While HRXCT provides information on the X-ray attenuation, which is depending on the internal density and atomic number of the component minerals, µ-XRF allows obtaining element-specific images of a sample surface. For the µ-XRF experiment, the sample is illuminated with a poly- or monochromatic X-ray beam and the characteristic fluorescence radiation emitted by the sample is detected with an energy dispersive detector. As the energy of the fluorescence radiation depends on the atomic number, elemental identification is possible. By scanning the sample along a vertical and horizontal raster through a micro-focus X-ray beam, two-dimensional images of the elemental distributions can be obtained. HRXCT was used to examine porous limestone and sandstone. The 3D analysis software Morpho+ was used for extraction of 3D data of the pore network. Additionally HRXCT and X-ray radiography were used to monitor liquid migration like water, water repellents and consolidants inside these stones and to detect their location in 3D. The same samples were examined with µ-XRF in order to localise the liquids based on their chemical composition. Both techniques can generate complementary 2D and 3D imagery of geological materials, opening up new gateways in the study of liquid migration inside porous rock types