may vary temporally, other than spatially, with the climatic season: like for the sulfates in Yoshimi Hundred Caves, almost all crystallizing during the dry winter season. The conditions of lower and variable RH are associated with more frequent cycles of crystallization/dissolution, hydration/dehydration, hygroscopic adsorption/desorption, and more damaging mechanical stresses generated on the stone. The rate of stone decay related to the simple interaction with liquid water, instead, upsurges in summer and early fall, when most precipitations are concentrated and typhoons may occur.
The results suggest that the chemistry of salt weathering is often controlled by the contribution of the rock-forming minerals. Another source that is worth mentioning is related to the efflorescences in Taya Caves that, given their composition and the presence of a cultivated land above the cave vault, is possibly represented by the agricultural chemicals used therein, which migrated downwards in solution.
Summary and conclusions
The studied sedimentary rocks share the silicate composition, often notable content in clay minerals, low strength, and very high porosity. The microenvironment of the underground sites under investigation is characterized by an extremely high humidity, and salt weathering occurs more easily where/when the RH is lower and inconstant, and the cave walls are not wet. Sulfates are the most common secondary phases, especially gypsum, which has low solubility and the highest DRH, crystallizing even when the RH is close to 100 %. In this regard, the pyrite contained in the rock seems to be the main precursor. On the other hand, water-driven deterioration is greatly affected by the abundance of clay minerals.
These preliminary results need further investigations, which will concern the continuation of the 226microclimatic monitoring for at least one entire year, the chemical analysis of rainwater and the groundwater collected in the caves, and the finalization of salt sampling and analysis in different seasons.
The completion of this research will serve as support for the conservation and valorization of the underground cultural heritage of Japan that, because of its own understated form and the low-key advertisement, is often not well known and out of the main tourist circuits.
Acknowledgements
This research was funded by JSPS (Japan Society for the Promotion of Science), under a postdoctoral fellowship “standard” granted to L. Germinario (ID no. P18122).
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227
MATERIAL CHARACTERIZATION AND DECAY OF THE LIMESTONES USED IN HISTORICAL STRUCTURES OF MARDİN, TURKEY
Felat Dursun
IN: SIEGESMUND, S. & MIDDENDORF, B. (EDS.): MONUMENT FUTURE: DECAY AND CONSERVATION OF STONE.
– PROCEEDINGS OF THE 14TH INTERNATIONAL CONGRESS ON THE DETERIORATION AND CONSERVATION OF STONE –
VOLUME I AND VOLUME II. MITTELDEUTSCHER VERLAG 2020.
Dicle University, Department of Mining Engineering, Diyarbakır, Turkey
Abstract
Situated on a scenic hillslope overlooking the Mesopotamian plain, Mardin bears the traces of many civilizations from prehistoric to modern times. With its highly crafted historical structures, Mardin significantly contributes to the cultural heritage of Turkey. Most buildings of architectural heritage in Mardin and its surroundings are constructed with the locally quarried limestone. Like many other historical buildings, the historical structures located in Mardin are also suffering from stone deterioration. This deterioration of the structures damages their integrity, aesthetic value and structural stability. The major aim of this study is to investigate the material characterization of the limestone in which the historical structures of Mardin were constructed. In order to identify the physico-mechanical and petrographic properties of rock material, it is essential to analyze their index properties. For this purpose, limestones from different quarries were collected for laboratory studies. To determine their physical and mechanical properties, such parameters as effective porosity, water absorption, uniaxial compressive strength, thermal conductivity, volumetric heat capacity, saturation coefficient and wet to dry strength ratio of the material were studied. In addition to this, the major deterioration forms were determined. It is understood from the experimental studies that the presence of water has a great impact on the durability of the material. Moreover, it is observed that efflorescence, erosion, alveolization, scaling, and deposits are the most common weathering forms developed on the historical structures of Mardin.
Keywords: Decay, limestone, physico-mechanical properties, weathering, Mardin
Introduction
It is known that all naturally occurring materials on the earth’s surface are subject to destructive weathering processes, whether in their natural settings or in construction. Weathering is a continuous and destructive process that changes the characteristic properties of stone. The weathering of stone may result in the loss of integrity, aesthetic value and structural stability of the historical structures. Even a small amount of surface weathering may deteriorate priceless pieces of monuments (Bristow 1990; Vincente et al. 1993; Siegesmund et al. 2002). Stone monuments are the most visible and essential structures of our cultural heritage; however, many of the historical structures around the world are now suffering 228from the above-mentioned weathering and associated deterioration (Fitzner et al. 2002). Mardin is a historical city situated in southeastern
