Evaluation of Fluid Transport Characteristics in Natural Stones Using Dual Source X-Ray Radiography

Abstract: This paper deals with experimental investigation of fluid penetration processes in natural stones by utilization of X-ray radiographical methods. Long-term exposure of building materials to weathering effects leads to their deterioration and consequently to reduction of the building’s bearing capacity. Here understanding of fluid transport processes in porous natural stones is fundamental for development of appropriate measures (e.g. conservation, consolidation) for their mitigation. In our previous study we investigated fluid penetration process in porous Maastricht calcarenite commonly used for restoration purposes experimentally by real-time radiography as well as numerically by utilizing finite element method (FEM) for simulation of steady-state fluid flow through a porous medium. Here, we extend our findings by employment of advanced dual-source/dual energy (DSCT/DECT) radiographical system TORATOM designed as a multi-purpose X-ray imaging device equipped with two pairs of X-ray tubes and detectors in an orthogonal arrangement with independent control of beam parameters. The device developed at the Centre of Excellence Telč was used for real-time dual source observation of fluid penetration process in two mutually perpendicular directions in specimens with fluid source/specimen width ratios 0.06 - 0.1. Furthermore, DSCT measurement of intact sample was used to develop detailed volumetric model of the investigated material for 3D FE simulation of the penetration process. The radiographical measurements were used to evaluate saturation characteristics (i.e. saturation time/saturation depth and saturation depth/saturated volume ratios) in two different scenarios to improve understanding of natural processes during in-situ water uptake measurements and application of conservation methods on historical objects.