Non-destructive microtomography-based imaging and measuring laboratory-induced degradation of travertine, a random heterogeneous geomaterial used in urban heritage

Abstract

The aim of this study is to apply X-ray microfocus computed microtomography (μ-XCT), a promising non-destructive 3D microscopy imaging technique, based on measurements of X-ray linear path attenuation coefficient, in order to study a Portuguese travertine, a random heterogeneous geomaterial used in urban heritage constructions. This study evaluates the impact of soluble sulphate salt–induced decay phenomena on texture characteristics at a micrometric scale. This is done to better describing, imaging, measuring and understanding the impact of an artificially induced sulphate-decay process on petrographic/petrophysical properties. A Portuguese travertine was chosen as the object of our study. Its laboratory-induced changes were systematically monitored, using non-destructive techniques, to determine voids (pores + fractures)/matrix fractions and size spectrum evolution based on 3-D images. This investigation demonstrates that the μ-XCT potential constitutes a valid complementary tool when analysing decay processes of complex natural materials in different environmental conditions. It clearly provides suggestive and important qualitative and/or quantitative estimates, at different spatial scales, of environmentally induced stone voids/matrix network spatial structure-texture evolution correlations. Further qualitative/quantitative parameterization assessment and statistical validation will be the next step to be taken on this study.