2-D image analysis: A complementary tool for characterizing quarry and weathered building limestone

The understanding of weathered processes and, more generally, of transfer properties of building stones, requires a detailed knowledge of porosity characteristics. This study aims to analyze two-dimensional (2-D) images of stones by using mathematical tools that enable the description of the pore and solid phase distribution. We selected two limestones that have been widely used for different types of buildings: a quarried and weathered Tuffeau stone (the latter being used in most châteaux of the Loire) and a quarried Sebastopol stone selected for numerous buildings in Paris. Backscattered electron scanning images obtained on thin sections of the stones were studied by using autocorrelation function analysis and chord distributions. Results showed that these mathematical tools are able to discuss, quantitatively and statistically, differences of pore and solid distributions between quarried limestones, and to discuss the degree of weathering of stones collected from buildings. Thus, very small differences of pore and solid phase distribution between the samples studied were revealed by chord distribution analysis and autocorrelation function analysis. Resulting characteristics obtained with such an analysis are promising information for a better understanding of weathering mechanisms.