Evaluation of stones to be used instead of Küfeki stone in historical buildings in İstanbul

Küfeki stone, a fossiliferous limestone, is one of the essential stone types in many monumental structures and historical buildings constructed throughout the history of İstanbul. For this reason, selecting a suitable stone instead of the Küfeki stone is a critical issue in restoration. In this study, the petrographic, mineralogical, physical, and mechanical properties of travertine and different types of limestone obtained from quarries close to the region, which have been used instead of Küfeki stone in restorations so far, were compared with the properties of Küfeki stone. After all analyses and experiments, microscopic and petrographic analyses were found to be determinative studies in interpreting the physical and mechanical properties of the stones and the effects of durability tests on them. In addition, it is important to perform color and ultrasonic velocity measurements as they are easily applicable, non-destructive methods in the field and provide interpretable and meaningful results. Care should be taken to ensure that the durability tests planned to be carried out represent the environmental conditions of the structure where the stone will be used. The stones most similar to Küfeki in matrix and allochem type generally gave the most compatible results.