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    Material Characterization and Damage Assessment of Byzantine Rock-Cut Monastery: A Case Study of Kiyikoy Hagia Nicholas
    (Istanbul Univ, Research Inst Turkology, Dept Art History, 2024) Ozata, Serife; Akturk, Buesra; Akturk, Engin
    Rock -cut historical structures have been constructed worldwide for various functions throughout history, including during the Byzantine Empire. The Kiyikoy Hagia Nicholas Monastery is an exceptional one of the surviving rock -hewn buildings in the Thrace Region. It has a basilical plan and was constructed in the Early Byzantine Period. The study goals are to provide original material characterization, suggestions for damage prevention and conservation measures for rock -cut structures of Byzantine architecture through this monastery case. Therefore, firstly the distinct architectural style of the building was revealed through a comprehensive analysis and by comparing it with similar structures. Then, a damage reconnaissance was performed and material samples were subjected to mechanical, physical, and chemical analyses and acid treatment experiments. Investigations focused on identifying the original materials and understanding the reasons for various decay and damage types observed in the monastery. Proposals for materials compatible with the original material, considering physical, mechanical, and chemical properties, were developed. The effectiveness of the characterization methods was explained. To prevent the effect of cracks, which is the main structural damage, constructing strengthening structural elements by using suitable materials was recommended. For non-structural damages, the removal of moisture in the main rock was recommended, and possible actions for surface cleaning, conservation and consolidation were described. It is concluded that the documentation, diagnostic and restoration steps developed for this monastery can be applied to similar Byzantine rock -cut structures.
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    Utilization of waste Cappadocia earth as a natural pozzolan in alkali activation: A parametric study
    (Elsevier Sci Ltd, 2022) Ozata, Serife; Akturk, Busra; Yuzer, Nabi
    This study presents the investigation of the possible use of rock-cut carving waste earth in Cappadocia as a precursor in alkali activation. The Cappadocia waste earth was activated by sodium hydroxide (NH) and sodium silicate (WG). In addition, slaked lime (CH) was substituted as a calcium resource. The compressive strength development was determined and the reaction mechanisms were investigated through X-ray diffraction and Fourier transform infrared spectroscopy. It was found that different strength levels can be obtained, depending on the activator type and CH-substitution ratio. While WG-activated mixes presented higher early age values, NH-activated mixes presented higher values at further ages, i.e., ~17 MPa at 28 days. The CH substitution enhanced the compressive strength for both early and further ages, attributing to the available Ca2+ ions resulting in the formation of C-A-S-H gel. The XRD results showed that silicates group minerals prominent in control mixes, while C-A-S-H-like gel was the primary phase in CH-substituted mixes. N-A-S-H and other hydrated compounds were found in all mixes, responsible for strength increment. Moreover, secondary electron microscope images revealed a denser structure in WG-activated mixes. Results of energy dispersive spectroscopy and X-ray diffractions corroborated hydration products and alkali activation. The obtained results of this study depict that alkali-activated Cappadocia earth can be a feasible and alternative sustainable binder to be used as a structural material.