Bayer, Karol; Weber, Johannes:

Kalknanosuspensionen zur strukturellen Festigung von porösen Kalksteinen – eine kritische Bewertung der Anwendungs-möglichkeiten und –grenzen.

Der Beitrag ist auf die Anwendung von alkoholischen Calciumhydroxid-Nanosuspensionen für die Festigung von porösen Kalksteinen fokussiert. Es wird eine Reihe von Ergebnissen und Erfahrungen einer systematischer Prüfung sowohl an Serien von Prüfkörpern und auch an realen Denkmalobjekten vorgestellt. Bei der Bewertung der Konsolidierung und Optimierung der Applikation wurde eine Vielzahl von verschieden Methoden eingesetzt – von der einfachen visuellen Charakterisierung bis zu instrumentellen Verfahren. Z. B. wurden zur objektiven Evaluierung mikroskopische Methoden wie Polarisationsmikroskopie und Rasterelektronenmikroskopie, dann Ultraschall- und Farbmessungen gebraucht. Dies ermöglicht eine Evaluierung der Konsolidierungsergebnisse und auch einen sachlichen Vergleich von verschiedenen Kalknanosuspensionen. Aufgrund der Untersuchungen an Prüfkörpern wurden folgend die Kalknanosuspensionen an ausgewählten Referenzobjekten für strukturelle Festigung eingesetzt und die Festigung bewertet.
Im Beitrag werden Ergebnisse zusammengefasst, die im Rahmen von drei internationalen Projekten (Stonecore, Nanoforart und Nanolith) erzielt wurden.

Lime nanosuspensions as consolidants for porous limestones – a critical evaluation of the possibilities and limits of application.

The contribution is focused on the applicability of alcoholic nanosuspensions of calciumhydroxide for the consolidation of porous limestones. Based on systematic examination both on laboratory specimens and real objects, various results and practical experiences are presented. A number of methods were employed to evaluate and optimize the product application, ranging from simple visual means to instrumental methods. Thus, techniques such as polarizing and scanning electron microscopy were used as well as ultrasound and colour measurements. In this way, the effects of consolidation were assessed and an objective comparison was made between different types of lime-nanosuspensions. Based on tests with laboratory specimens, the products were then applied on reference objects and their consolidation effect was evaluated.
The contribution summarizes the main results achieved in the frame of three international projects, namely Stonecore, Nanoforart and Nanolith.

Karol Bayer MSc. is a conservation scientist working at the Faculty of restoration / University Pardubice, currently the dean of the Faculty since 2009. In the past (1984-1995) he was employed at the Institute for the Care of Monuments as part of the Slovak Republic State Studios for Restoration / Department of Technology, Bratislava, Slovak Republic. Since 1993 he has also worked as an external lecturer at the University of Applied Arts in Vienna / Institute of Restoration and Conservation. His main teaching and research activities are focused on material characteristics, decay and conservation of stone, architectural surfaces and wall paintings. In the frame of research work he concentrates mainly on the analysis and characterisation of historical mortars as well as the use of nanomaterials for the conservation of stone and architectural surfaces. He has been involved in several international research projects e.g. NANOLITH; Application of nanomaterials for sustainable conservation of historical works of sculpture and architecture constructed of Leitha limestone; NANOFORART, Nano-materials for the conservation and preservation of movable and immovable artworks; STONECORE, Stone conservation for the refurbishment of buildings, ROCARE, Roman Cements for Architectural Restoration to New High Standards; ROCEM, Roman Cement to Restore Built Heritage Effectively or NAMO, Nabatean Mortars – Technology and Application.

Prof. Johannes Weber is a conservation scientist graduated in petrology. Since 1984 he has been working at the University of Applied Arts Vienna where he is currently holding the position of a Professor and is Head of the Department of Conservation Sciences.
Within the student courses of conservation and restoration, both at the University of Applied Arts and the Academy of Fine Arts Vienna, the lectures of Prof. Weber are focused on material sciences related to the conservation of stone, mortar, mural paintings and ceramics. His main fields of research are in the areas of historic mortars from ancient times up to the early 2th century, the optical examination of microstructural decay and consolidants in porous mineral materials, and the action of soluble salts in response to climatic cycles. The main methodical expertise is based on microscopy and SEM. Prof. Weber has been participating in several national and international research projects, including R&D projects of the European Commission in FP4, 5 and 7 and Horizon2020. From 2009-12, he has been coordinator of the EU project FP7-ENV-2008-1, No. 226898 ROCARE. Currently, he is consortium member of the EU project No. 646178 Nano-Cathedral. Currently five PhD-theses are performed under the supervision of Prof. Weber.