Investigation on the physico-mechanical properties of the materials used in the historical structures: A case study of Cizre Castle (Birca Belek)

Historical structures are the most important relics of the history of a society. Locally available materials have been used in most of the historical structures. Natural stones specific to the region are often used in historical buildings. Basalt has been used a lot in historical buildings due to its strenght and durability. It has been observed that, in some historical structures, basaltic stones have been used together with limestones. Although this use is generally considered aesthetically preferred, research on the use of two materials together is limited. As a result of the observation on historical structures located in Cizre( a town of Sirnak province), mostly basalt has been used in historical buildings and limestone has been used in some details. Birca Belek (Belek Bastion) has been chosen to be investigated this study because of those facts; It is registered historical masonry structure that has not been restored before and basalt-limestone were used together. This bastion has a square structure compared to normal bastion. This bastion consists of a row of limestone and a row of basalt stones. As a result of observational reviews in Birca Belek was seen that the most common forms of deterioration in the bastion were material loss, discoloration and biological colonization. These deteriorations are mostly located on the northern façade and in limestones of the bastion. For determine the physic-mechanical properties of the stones used in Birca Belek, possible basalt and limestone quarries were identified, which are thought to have supplied the stones used in this bastion. Fresh samples have been taken from these determined quarries. Physic-mechanical properties such as dry and saturated unit volume weight, mass water absorption capacity, porosity, dry and saturated P ultrasonic wave speed, thermal conductivity and single-axis pressure resistance of fresh basalt and limestone samples have been determined. In addition, aging tests such as MgSO4 and Na2SO4 salt crystallization were performed to determine deterioration behaviour. These studies will be an important data source for the stone structure in terms of defining the physic-mechanical properties of basalt and kietas and predicting deterioration behaviour. Fresh basalt and limestone samples and basalt and limestone samples taken from Birca Belek, thin section, XRD and XRF results showed that the thermal conductivity coefficient of the 1st group of limestones close to the limestones in Birca Belek was higher than in other groups and this was associated with crack development in limestones in the structure. As a result of all these studies and determinations, it was determined that it would be appropriate to use basalts from the possible quarry designated as basalt in Birca Belek and 1st group of limestone as limestone in future restoration studies. This determination needs to be confirmed with regular examples from the Birca Belek bastion.