Characterization of Pyroclastic Stones in the Cut Rock Historical Architecture of Kandovan Village

Kandovan historical village, in the vicinity of Osku town is one of the most important attractive sites in East Azerbaijan province which is outstanding and prominent due to the hewn-cut house of rock skirt of the Sahand volcano. This site has been registered in 1998 on the national cultural heritage list of Iran. Kandovan rocky architecture, from geological point of view, is on the surfaces of a thick ignimbrite layer that this layer, due to natural weathering and erosion along the main joints and discontinuities of Kandovan valley, has created conical forms and structures. According to the existing theory, Kandovan village was inhabited and settled in these conical buildings since the Ilkhanid era. Recent developments on rock decay in rock-cut architecture of the Kandovan historical village, have heightened the need for recognizing the role of different factors of weathering process on this site. Therefore, the main objective of this study was to assess the effect of inherent vice as a fundamental factor in deterioration patterns. For this purpose, field and laboratory investigations like sampling and observation, characterization with thin section petrography and X-ray diffraction analyzes, along with the measurement of physical properties and durability of rock in rocky houses, the role of inherent vice rock with intensity of rock mass Kandovan weathering has been done. Nowadays, intensity of decay and weathering in Kandovan village rocks causes of poor living conditions, ruination, and seasonal residence or nonresidential conditions. Based on the rock characterization, water absorption, dry density, total porosity content, saturation coefficient, slake durability and experiment for resistance to freezing-thawing demonstrated that Kandovan ignimbrite rock have poor durability and high sensitive to predisposing factors to deterioration such as wetting and drying and freezing-thawing cycles. The collection of these inherent properties causes of the internal structure to be non-resistance to the tensions arising from the impact of climate cycles. The local climate could be considered (or suggested) as the main reason of weathering and erosion of this rocky architecture.