Physicochemical characterization and a GIS analysis of the historical mortar of the masonry concerning a nineteenth-century monument

This study provides a detailed physicochemical characterization of historical mortar from a nineteenth-century church in Ilia, near ancient Olympia (Peloponnese, Greece), a monument of high cultural and architectural significance currently undergoing restoration planning. Mortar samples were examined using polarized optical microscopy, scanning electron microscopy, X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy with attenuated total reflectance, thermogravimetric analysis, nitrogen adsorption-desorption isotherms, microelectrophoresis, and equilibrium pH measurements of mortar–water suspensions. The analyses confirm that the material is a lime-based mortar with predominantly calcareous aggregates and minor aluminosilicate and iron-bearing phases. Petrographic observations revealed rounded aggregates of varying sizes, shrinkage cracks, and a layered binder microstructure that generates meso and macroporosity. This pore network facilitates capillary moisture rise, causing binder depletion and progressive deterioration, particularly in lower masonry sections. Surface chemistry data indicate a low electrical surface charge and slight acidity, suggesting limited vulnerability to direct corrosion from atmospheric pollutants such as SO₂ and NOx. These results underline the importance of using compatible repair mortars that replicate the texture, porosity, and composition of the original material, alongside moisture-management interventions at the masonry base. Petrographic and mineralogical evidence further associates the aggregates with nearby Gavrovo-Tripolis geotectonic formations, providing a local source reference for restoration materials. Combining GIS analysis with scanning electron microscopy-energy dispersive X-ray spectroscopy data also demonstrates that mortars used in the surrounding region during the same period share similar characteristics. To our knowledge, this is the first study to apply electrophoretic mobility and equilibrium pH measurements to historical mortars, offering novel insight into their surface properties. By integrating traditional mineralogical and petrographic techniques with advanced surface chemistry analyses, this work sheds light on the deterioration mechanisms of historic masonry mortars and delivers a comprehensive framework to guide the conservation and restoration of heritage structures.