material.
Calibration procedures are developed, and tests are carried out to highlight the degree of saturation by mean of electrical and IR thermography imaging. The identification of the material properties (like petrophysical properties) can be used to describe phenomenological patterns affecting the in-situ structure. Nevertheless, such point of view must be completed to highlight accurately the water content and its evolution to better understand the damages and evolution of the historical monuments.
The two combined methods seem to be well adapted to characterize the water transfer in the structures and for a better accuracy of the proposed diagnosis, the conclusions coming from another calibration scenario will be added.
Such a combination of NDT is very promising regarding other generally used methods.
References
D. Benavente, G. G.-H. Cultrone, The combined influence of mineralogical, hygric and thermal properties on the durability of porous building stones, Eur. J. Mineral. 20 (2008) 673–685.
ICOMOS ISCS, Illustrated glossary on stone deterioration patterns. Monuments and Sites XV, 2008.
EUROPEAN STANDARD EN 16682: Conservation of cultural heritage – Methods of measurement of moisture content in materials constituting immovable cultural heritage, European Committee for Standardization, Brussels, 2017.
V. Di Tullio, N. Proietti, M. Gobbino, D. Capitani, R. Olmi, S. Priori, C. Riminesi, E. Giani. Non-destructive mapping of dampness and salts in degraded wall paintings in hypogeous buildings: the case of St. Clement at mass fresco in St. Clement Basilica, Rome, Analytical and Bioanalytical Chemistry, vol. 396, no 5, p. 1885–1896, 2010.
E. Grinzato, N. Ludwig, G. Cadelano, M. Bertucci, M. Gargano, P. Bison, Infrared thermography for moisture detection: A laboratory study and in-situ test, Mater. Eval. 69 (2011) 97–104.
M. A. Hassine, K. Beck, X. Brunetaud, M. Al-Mukhtar, Use of electrical resistance measurement to assess the water saturation profile in porous limestones during capillary imbibition, Constr. Build. Mater. 165 (2018) 206–217.
D. Vermeersch, Le complexe religieux des Vaux-de-la-Celle à Genainville (95): nouvelle proposition de phasage du sanctuaire d’après les dernières fouilles, in: Etudier Les Lieux Culte Gaule Romaine, 2009.
BRGM, Carte géologique 1/50 000, feuille de: MANTES-LA-JOLIE, (1974).
257
EXPERIMENTAL CONSERVATION AND FIRST INVESTIGATIONS ON THE WEATHERING OF GEGHARD MONASTERY (ARMENIA)
Wanja Wedekind1, Emma Harutyunyan2, Nevenka Novakovic3, Siegfried Siegesmund1
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.
1 Geoscience Centre of the University of Göttingen, Goldschmidtstr. 3, 37077 Göttingen, Germany
2 National University of Architecture and Construction of Armenia, Teryan 105, 0009 Yerevan, Armenia
3 Cultural Heritage Preservation Institute of Belgrade, Kalemegdan Gornji grad 14, 11000 Belgrade, Serbia
Abstract
The mediaval monastery of Geghard is located in the Kotayk province of Armenia in the Azat River Gorge. Since 1986, the stone formations and the monastery are included in the UNESCO World Heritage List.
The main church was built in 1215, whereas the monastery complex was founded much earlier in the 4th century by Gregory the Illuminator. The church is constructed out of basalt ashlar. Parts of the monastery complex are carved from the rock formation of the Azat Valley.
Onsite investigations were carried out, and the petrophysical properties of the different building stones were investigated.
Further investigations show a high impact of hydric dilatation and a potential sensitivity to salt weathering on the rock parts of the monastery. Experimental conservation was carried out to reduce the hydric dilatation and to strengthen the poor hardness of the rock material.
Introduction
The Geghard Monastery is an outstanding example of the pinnacle of Armenian medieval architecture (Fig. 1a).
The complex of medieval buildings contain a number of churches and tombs, some of which are cut into the natural rock (Fig. 1b to d, 3a).
In 1679 the monastery was badly damaged by an earthquake. Restoring the monastery for the purpose of tourism started in the first half of the 20th century. This includes the relatively new roof made of basalt in the 1980s.
Geology
The Geghard Monastery is located some 40 kilometres east of Yerevan, 1650 m above sea level.
Armenia is located in the northeastern part of the Anatolian–Armenian–Iranian plateau (Meliksetian et al. 2014). During Armenia’s entire geological history, the country was subjected to volcanic activity. Most building stones are therefore tuffs and basaltic rocks.
Methods of investigation and experimental conservation
Petrographic analyses of the material were done on thin sections under a polarization microscope. Hydrostatic weighing on sample cubes of 65 mm edge length was carried out to acquire the particle and bulk density as well as the porosity (DIN 52102). The saturation degree S was determined by the 258quotient of unforced (atmospheric conditions) and forced (vacuum) water saturation. On sample cubes of 65 mm edge length, the capillary water adsorption (w value) was measured in a closed cabinet while weighing over time (DIN EN ISO 15148). Mercury intrusion porosimetry was used to acquire the pore radii distribution (Fig. 2g and h).
Figure 1: a) The Geghard Monastery complex, Upper Azat Valley. b) The prayer hall of the Kathoghike Church built from basalt. c) Rock cut tombs and cross stones. d) The Jamatoun of the Proshian cut into the rock.
The hydric expansion of the tuff rocks was measured on square samples (diameter 15 mm, length 100 mm) under conditions of complete immersion in demineralized water. A displacement transducer with a resolution of 0.1 µm measured the linear expansion as a function of time. Ultrasonic velocity was measured by using a pundipLap+ device (proceq). Surface hardness measurements were done in situ as well as on stone samples in the laboratory. For the measurements an Equotip 3 (proceq) portable testing device
