Monument Future - Siegfried Siegesmund

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OF STONE –

       VOLUME I AND VOLUME II. MITTELDEUTSCHER VERLAG 2020.

      Istanbul Technical University, Turkey

       Abstract

      The historic fortresses and bastions that constitute the defense system of Bosporus, have ceased to be used by military units after losing their strategic importance in time and later they have been abandoned. Rumelifeneri Fortress which is a part of this defense system dates back to the 18th century. Today the most prominent problems of the fortress are; the ongoing process of deterioration caused by environmental impacts, due to its location by the sea and the uncontrolled influx of visitors. In terms of the study, to make a complete description of deterioration types, firstly a deterioration mapping is prepared. Samples were taken from different parts of the structure and chemical, physical and petrographic analyses were conducted in order to analyze the characterization of the original materials and types and degrees of deterioration. As a result of the analyses, the types and degrees of deterioration observed in building stone basaltic andesites, the main building material of the structure, were identified and classified. The characterization of the mortars and plasters are also completed; such as binder, aggregate ratios and the aggregate size distribution and the types of the aggregates. According to these results, suggestions and interventions have been developed for the parts of the structure that should be primarily conserved. This study aims to draw attention to these structures which are an important part of the historical and cultural heritage of Eurasia, by analizing characterization and deterioration of materials of Rumelifeneri Fortress.

      Keywords: Cultural Heritage, Deterioration of Igneous Rock, Military Architecture, Mortar Characterization, Stone Conservation, Waterfront Fortresses

       General Information and Description of the Site

      The Bosphorus, forming the continental boundary between Asia and Europe, is an approximately thirty km long natural waterway connecting the Black Sea to the Marmara Sea. Fortifications were built on both sides of the Bosphorus starting from the Byzantine period. Rumelifeneri Fortress is an authentic example of the Bosphorus’ defense system dating back to 18th century during the Ottoman period. The fortress was built on a promontory volcanic rock near Rumelifeneri Lighthouse located at the northernmost point on the European side of the Bosphorus. (Figure 1).

      The fortress has a rectangular plan with two beveled corners on the seafront with approximate dimensions of 55 m to 70 m (Karadağ 2003) (Figure 2). Stones were used as ashlar stones on faces and as rubble in the core of the casemate walls.

      48Bonding timbers were used all around the walls on the springing line level of embrasure arches and 1.85 meters above this level. Arches of embrasures and the dome in the eastern tower were built with bricks measuring 34 × 34 × 3 centimeters.

      Figure 1: Rumelifeneri Fortress (Url-1 2017).

      Figure 2: Plan of Rumelifeneri Fortress (Eyüpgiller and Yașa 2019), the location of samples.

       Scope of the Study and Methodology

      This study reveals the characteristics and deteriorations of the stones and mortars of Rumelifeneri Fortress within detailed field studies and laboratory analyses. Visual observations on the site indicate that the northeastern façade represents nearly all of the deteriorations. Thus, a mapping of the façade was prepared to obtain complete identification of geology of the area and all deteriorations based on the architectural survey and rectified photographs (Figure 3).

      The geological formation of the area is called “Garipçe Formation” which is from Upper Cretaceous and Lower Eocene era. The fortress is located on the lava of Rumelifeneri which consists of andesite and basaltic andesite. The location has two layers of lava, the later phase lava is grey and black colored while the earlier phase lava is reddish and dark brownish. (Yavuz and Yılmaz 2010). Thus, these two different basaltic andesite lavas were identified as Lava 1 (reddish colored) and Lava 2 (grey colored). ICOMOS – ISCS Illustrated Glossary on Stone Deterioration Patterns was used for defining the deterioration types (ICOMOS 2008) and different levels of stone deteriorations (differential erosion, alveolization and coving) were shown with different shades of the same color for each stone type. Besides, discolouration (black), calcite encrustation, salt crust, lichens and graffiti were also observed on the façade and indicated on the mapping. In addition, all of the deterioration types were gathered together on a table to create a deterioration glossary for the building (Figure 4).

      Figure 3: Mapping of deteriorations on northeastern façade, April 2019.

      Figure 4: Deterioration types encountered on Rumelifeneri Fortress.

      Laboratory studies were carried out for characterization of the materials used on the building. Within this context 13 samples (10 mortar and 3 stone) 49were taken from both sound and deteriorated parts of the building. Locations of the samples were indicated on the scaled drawings (Figure 2, 3). The details about the samples can be seen in Table 1. The sampling was followed by laboratory analysis. Chemical and physical analyses were conducted on the samples to determine the characteristics of the original materials and the causes and the depth of deterioration. Acid loss test, sieve analysis, ignition loss test, protein and oil spot tests were performed on mortars. The water soluble salt content of the mortars was also analyzed. (Pekmezci and Ersen 2010; Güleç and Ersen 1998; Middendorf et al. 2005; Teutonico 1988; KUDEB 2011). The stone samples were examined by using SEM-EDS.

Sample No Description
M1 Masonry mortar with yellowish colored binder, stone and seashell aggregate under 5mm
M2 Masonry mortar with white colored binder, sand and seashell aggregate under 3mm
M3 Masonry mortar with yellowish colored binder, stone aggregate under 8mm
M4 Masonry mortar with white colored binder, stone and seashell aggregate under 5mm
M5 Strong masonry mortar with white colored binder, stone & seashell aggregate under 8mm
M6 Strong joint mortar with white colored binder, stone & seashell aggregate under 2mm
M7 Masonry mortar with white colored binder, stone and seashell aggregate under 6mm
M8 Strong mortar with yellowish colored binder, stone & seashell agg. under 4mm
M9 Plaster with pinkish colored binder and brick aggregate under 4mm
M10 Strong masonry mortar with yellowish colored binder, stone aggregate under 1mm
S1

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