Geochemical and physical properties of historical mortars from the Tyana Octagonal Church: implications for restoration

Abstract This study aims to investigate the mineralogical, petrographic, geochemical, and physical properties of mortar samples from the Octagonal Church in the Ancient City of Tyana using multiple analytical methods to provide critical data for both the characterization of ancient building materials and the restoration process. Mortar samples were analyzed by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM-EDS), X-ray fluorescence (XRF), salt tests, grain size analysis, water absorption capacity, unit volume weight, and porosity analysis. The findings show that the mortars are largely composed of local materials, which are compatible with the geological structure of the region. The findings indicate that the mortars were made of local materials and contained air-hardening calcite and gypsum. High CaO and MgO contents indicate the use of dolomitic lime, while high porosity indicates the risk of water-salt interaction deterioration. This study provides important data for the preservation and durability of the mortars of the Octagon Church.