Deterioration of different stones used in historical buildings within Nigde province, Cappadocia

Abstract

The Cappadocia region hosts various historical buildings constructed by several civilisations from long in the past until more recently. Some of these are big and significant buildings and their artistic, cultural and aesthetical features are quite attention-grabbing. The stones used in most of these buildings have deteriorated due to various effects. The correct identification of the deterioration mechanisms is of fundamental importance to design retrofitting and restoration procedures. In this study we aimed to determine the engineering properties and deterioration of the stones widely used in the different historical buildings in the Nigde region that forms the southern boundary of Cappadocia. 17 block samples (2 marble, 2 travertine, 6 tuff, 5 ignimbrite and 1 andesite) were taken – in accordance with the obtained permits – from stones that had fallen from the buildings and could not be used again as part of any restoration. With the purpose ofidentifying the deterioration of the building stones due to their geological structure and external effects, chemical and petrographic analyses were conducted along with detailed field observations. To determine the geomechanical properties (dry unit weight, water absorption, effective porosity, P-wave velocity, uniaxial compressive strength, slake durability index, capillary water absorption, Bohme abrasion value and Schmidt hammer rebound value) of the stones comprehensive laboratory research was carried out. The main cause of the deterioration observed in ignimbrites (UK3) and tuffs (AK3) with low strength and high porosity was humidity, especially at the capillary level. Significant deterioration observed on some stone samples was also due to the use of stones that exhibited poorer properties than the rest, although they came from the same quarry. Adding the negative effects of ground and surface water on top of these, severe damage on the stones in the formof flaking, discolouration and loss of strength were observed.