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Damage phenomenon and petrophysical properties of sandstones at the Phnom Bakheng Temple (Angkor, Cambodia): first investigations and possible conservation measures

Wanja Wedekind, Christian J. Gross, Andreas Hoffmann, Siegfried Siegesmund

Received: 19 June 2018 / Accepted: 20 October 2018 / Published online: 31 October 2018

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Sandstones, clay in the form of bricks and laterite are the building materials used by the Khmer to construct the imposing

and magnificent temples in Southeast Asia. Many of these monuments suffer from fracturing, sanding, contour scaling, crust

formation and salt weathering. The affinity to weathering is closely connected to the type of material. Two sandstone types

classified as feldspathic arenite and quartz arenite of Angkor as well as two arkosic sandstones from Thailand are described

and investigated in this study. Important petrophysical properties determined for the different sandstones consist of hydric

expansion, thermal expansion, pore radii distribution and ultrasonic velocity. Different investigations such as capillary

water uptake, surface hardness, hygroscopic water sorption, and salt resistance tests were undertaken in the laboratory to

characterize the various rock types. Observations and quantified damage mapping were done onsite at the Phnom Bakheng

Temple. Contour scaling in the form of weathering crusts is one of the main deterioration features observable at the Angkor

monuments. Comparisons are made between the building stone, the crust material from the Phnom Bakheng Temple and

fresh stone material used for restoration. Significant differences in hydric and especially in thermal expansion of the crust

and sandstone have been determined. The results seem to indicate that extensional processes occur, which can be consid-

ered a force for detachment (i.e., contour scaling, flaking). In an experimental trial, the hydric and thermal expansion of the

weathering crust and the building stone was significantly reduced byusing a weak acid for the crust and a swelling inhibitor

for the original building stone.

All readers of the article via the shared link will also be able to use Enhanced PDF features such as annotation tools, one-click supplements, citation file exports and article metrics.

https://rdcu.be/bax9Y

Rock Characteristics and Weathering of Rock-Cut Monuments in Lycia (Turkey): Natural and Anthropogenic Hazards and Sustainable Preservation

Wanja Wedekind, Christian Gross, Rubén Lopez-Doncel

In book: 10th International Symposium on the Conservation of Monuments in the Mediterranean Basin

January 2018, DOI: 10.1007/978-3-319-78093-1_54, Springer International Publishing

The rock-cut architecture of the Lycian culture in Turkey was created around 500 BC to 400 AC. The remains are a testament to their building heritage. The Lycian builders created monumental sarcophagi and tomb facades with unique forms and aesthetic styles in the ancient Mediterranean world. Most of these magnificent monuments are cut into different limestone formations. They are located in an area along the southern coast of Turkey, known as Lycia after its creators. The rocks as well as the monuments are affected by weathering and disasters, such as the dissolution and precipitation of calcite, biological growth, and earthquakes. To characterize the weathering forms and processes, onsite investigations were done on several rock-cut monuments at four outstanding Lycian sites showing distinct geological characteristics. The investigated sites are Xanthus, Telmessos, Tlos, and Myra. The tombs are built into massive, thickly bedded light gray limestone. The limestones show a wide variety of rock fabrics. Onsite field investigations included quantitative mapping of damage phenomena, surface hardness measurements utilizing a Schmidt pendulum hammer, water absorption using Karsten test pipes, and closer observations using a digital microscope. Four different limestone fabrics were characterized by petrographic analysis of thin sections and with the cathodoluminescence microscope. These were collected from outcrop exposures near the monuments. Petrophysical measurements of the porosity and density were performed in the laboratory. Physical ultrasonic velocity measurements and micro-hardness measurements using an Equotip 3 device were done under dry- and water-saturated conditions. Weathering due to solution/precipitation is the main threat to the monuments and is strongly connected to the type of limestone. Another key factors the site-specific climatic condition.

Salt weathering and hygric expansion of tuff rocks in archeological sites in Central Mexico

December 23, 2019

Pötzl, C., López-Doncel, R., Wedekind, W., Siegesmund, S. (2016). 5th International Conference Youth in Conservation of Cultural Heritage YOCOCU 2016, 21st - 23rd September, Madrid, Spain, pp. 164-168

Natural stones have been used worldwide and across cultures as raw material for construction and artistic applications for hundreds of years. Due their large-scale availability in the Trans-Mexican Volcanic Belt (TMVB), volcanic tuff stones are popular building stones all over Mexico. They were used to build churches, pyramids, and other important monuments and have been used in more recent construction work.

If you are interested to read the whole article visit https://issuu.com/museoreinasofia/docs/v6yococu_-_baja.

The Saale-Unstrut cultural landscape corridor

Hoppert, M., Bahn, B., Bergmeier, E., Deutsch, M., Epperlein, K., Hallmann, C., Müller, A., Platz, T.V., Reeh, T., Stück, H., Wedekind, W., Siegesmund, S.

Cultural landscapes are the result of long-term human–environment interaction, but they are nevertheless worldwide vulnerable to processes of global change such as land-use change, urbanization, neglect and abandonment. The cultural landscape mosaic along the rivers Saale and Unstrut (Germany, Central Uplands) provides many features of (pre-)historical human activities, in particular since the Middle Ages. Most of these elements occur in what can be defined as “cultural landscape corridor” along the river valleys, thus conveying a broad insight in historic land-use, including viticulture, and architecture of the past centuries in a nutshell. The area has been nominated for inscription in the List of World Heritage, due to its famous components in Naumburg, Freyburg and Pforta that representatively reflect cultural processes of the High Middle Ages. However, population loss and land-use change as well as neglect of lower-ranking monuments may lead to a gradual decline of the historical cultural landscape and its multiple elements. In this contribution, we summarize the landscape development in the Saale-Unstrut area and discuss measures to raise awareness of selected elements of a coherent cultural landscape corridor.

Kann das Leiden der Apsaras geheilt werden?

Wanja Wedekind

Das sagenumwobene Angkor in Kambodscha war vom 9. bis zum 15. Jahrhundert der Herrschaftssitz des Khmer-Imperiums. Die sieben Königsstädte des historischen Angkor beherbergen die größten Tempel der Welt. Darüber hinaus war Angkor mit etwa 400 km2 die größte Städtesiedlung ihrer Zeit. Aktuelle Forschungen gehen davon aus, dass Angkor zu seiner Blüte- zeit von rund 1,5 Millionen Menschen bevölkert war.

Aufgrund des tropischen Klimas sind die Tempel Angkors verstärkt durch chemische und biologische Alterations- und Verwitterungsprozesse betroffen. Diese betreffen in erster Linie die biologische Besiedlung sowie das chemische Lösen und die Umwandlung von Mineralien. Die chemische Verwitterung sorgt für die Entwicklung von Verwitterungsprofilen und der Ausbildung einer Kruste an der Gesteinsoberfäche. Deutlich sichtbar sind rötliche Verfärbungen, die auf eine Oxidation von Eisen schließen lassen, sowie die Bildung von kompakten Krusten, die schalenartig abplatzen. 

Die veröffentlichten Forschungsergebnisse zeigen auf, dass die dramatische Schalenbildung, nicht in erster Linie auf Volumenveränderungen aufgrund von Feuchteaufnahme zurück zu führen ist, sondern thermischen Dehnungsprozessen geschuldet ist. Über experimentelle Konservierungsversuche an Testmaterial konnten die Dehnungsprozesse signifikant verringert werden. 

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