Assessment of the Current State of Construction Materials of Some Historical Monuments in Georgia

The study aims to assess the current condition of construction materials used in four significant historical monuments in Georgia - Sioni Cathedral (Tbilisi, VI-XI century), Anchiskhati Basilica (Tbilisi, VI century), Barakoni Church (Racha region, XVIII century), and Nikortsminda Cathedral (Racha region, XI century) - through mineralogical and physical-mechanical analyses. The methodology combines X-ray diffraction (XRD) analysis and standard physical-mechanical tests, and the results are compared with established reference values. XRD analysis revealed distinct mineralogical compositions for each structure. In Sioni’s tuff slabs (19th century), the dominant phases include quartz (40%), kaolinite, and Na-montmorillonite - all of which are highly hygroscopic and sensitive to moisture-induced degradation. Anchiskhati’s dressed tuff showed 25% quartz, Ca-Na feldspar, clay phases, and traces of kaersutite, indicating a relatively complex and weather-sensitive matrix. Barakoni’s dolomitic stone contains (Ca, Mg)CO₃ dolomite and CaCO₃ calcite, both susceptible to chemical weathering, especially from acid rain and salt crystallization. In Nikortsminda’s sandstone, dominant phases include calcite, quartz, and clinoptilolite (a zeolite), which contributes to increased capillarity and water retention, enhancing decay risks. Physical-mechanical analysis indicates significant deterioration across all sites: the porosity of the Sioni building material increased by 12.5%, water absorption increased by up to 5%, and the strength decreased by 24%. In Anchiskhati, the porosity increased by 5%, and the strength decreased by 28%. In Barakoni, the strength decreased by 38%, while the porosity of Nikortsminda sandstone increased by 33%, and the strength decreased by 29%. The results demonstrate that the presence of clay minerals, zeolites, and carbonates correlates with increased porosity, reduced strength, and higher susceptibility to environmental factors. These findings emphasize the necessity of tailored conservation approaches to ensure the long-term protection of Georgia’s architectural heritage.