Influence of stone conservation actions on the long-term weathering behaviour of natural stones

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The decay of natural stone depends on the mineral content, the binding behaviour, the pore space conditions as well as the type of stress and type of weathering. By the use of preserving agents, stone decay can be influenced or even reduced. This research project focuses on the stone decay after stone conservation over time. To evaluate the long-term effect of a stone conservation action under natural weathering conditions, the Deutsche Bergbaumuseum provides for this research proposal about 25-year-old weathered natural stones of a free exposure study. These samples are untreated as well as treated with water repellent agents or rather in combination with stone strengthener. They provide a unique material basis to analyse the stone decay of conserved stones and to develop a non-destructive testing measuring system based on unilateral NMR-technique. The depth-dependent correlation between stone weathering over time and degradation of active substances by the use of non-destructive testing methods is rarely examined. This research project aims to develop the NMR-technique in order to validate the long-term effect of stone protective substances. Aim of this proposal is the final conception of a scientifically proven database to generate weathering models for time-dependent stone decay. The main data basis for this aim consists of the measurement results of the analysed natural stones of the free exposure study. The results were determined by destructive as well as non-destructive laboratory investigations. These values will be merged in a GIS-assisted database and visualised on a web-GIS interface with open-access, so that future users can refer to the generated state of knowledge. Forecast models based on this database will enable the simulation of the parameter-dependent weathering potential of natural stones. This research project provides a technological development of a non-destructive testing method as well as a long-term structured performance test for repair measures.