Boone, Marijn

Cnudde, Veerle

De Boever, Wesley

De Kock, Tim

De Schutter, Geert

Dewanckele, Jan

Jacobs, Patric

Lanzón, Marcos

Van Hoorebeke, Luc

Vandevoorde, Delphine

Ghent University Academic Bibliography

Geophysical Research AbstractsVol. 14, EGU2012-9550-1, 2012EGU General Assembly 2012© Author(s) 2012Compatibility study and adaption of stone repair mortars for the Ledestone (Belgium)T. De Kock (1,2), D. Vandevoorde (1,3), M.A. Boone (1,2), J. Dewanckele (1,2), W. De Boever (1,2), M. Lanzón(4), G. De Schutter (5), L. Van Hoorebeke (2,6), P. Jacobs (1,2), V. Cnudde (1,2)(1) Research Group Sedimentary Geology and Engineering Geology, Department of Geology and Soil Science, Faculty ofSciences, Ghent University, Belgium, (2) Centre for X-ray Tomography (UGCT), Ghent University, Belgium, (3) Departmentof Conservation and Restoration, Artesis University College of Antwerp, Belgium, (4) Departamento de Arquitectura yTecnología de la Edificación. Escuela de Arquitectura e Ingeniería de Edificación ARQ&IDE, Universidad Politécnica deCartagena, Spain, (5) Magnel Laboratory for Concrete Research, Department of Structural Engineering, Faculty ofEngineering, Ghent University, Belgium, (6) Department of Subatomic and Radiation Physics, Faculty of Sciences, GhentUniversity, BelgiumOne of the main historic building materials in northern Belgium is the Lede stone. This arenaceous limestonefrom Lutetian age was excavated in the region of Ghent and Brussels and was transported northwards by mainrivers such as the Scheldt and Zenne. Thanks to this natural transport route, the stone in also found in many citieswhich lie abroad the excavation area, such as Antwerp (Belgium) and various cities in the Netherlands (Breda,Zierikzee, . . . ). Due to its dominant occurrence in our cultural heritage, it is frequently subjected to restorationand renovation works. Depending on the degree of decay, most frequent stone operations are cleaning, healingwith mortar or replacing it by (often exotic) fresh blocks.Originally, this limestone has a greenish-gray colour, but when being exposed to atmospheric conditions itacquires a yellowish to rusty coloured patina. The origin of the latter is most likely the oxidation of glauconiteminerals which are present in a few percent in the stone. In addition, the stone often demonstrates black crustformation due to sulphation. Cleaning of the stone often results in an excess removal of this black gypsum crustsand patina, thus exposing deeper parts of the stone which appear more greenish-gray again. When the stone issubsequently healed by adding repair mortar to damaged parts, the question rises which mortar colour is moreappropriate.The choice of repair mortar is greatly depending on commercial aspects. When handling entire facades onmonuments, a mineral mortar based on ZnCl is most often applied in Belgium. The big advantage of thismortar is its fast curing. Three colour types have been developed for the Lede stone in specific. However, thehardness of this mortar is sometimes in conflict with reversibility. For the handling of individual sculptures someconservators choose for the application of (hydraulic) lime mortars. The advantage of using such mortars is theirhigh compatibility and reversibility. The disadvantage, besides being more labour intensive than mineral mortarsbased on ZnCl, is that no specific recipes are yet developed for Lede stone and the result is thus dependent on theknowledge of the restorer. Both of the repair mortars have the problem that Lede stone changes its colour dueto ageing while the mortar itself remains colour stable. This means that if the mortar colour was adapted for aresemblance at the moment of application, the colour difference between stone and mortar will increase in time.In this study, the compatibility of the different stone repair mortars with the Lede stone are tested. Further,a study was made whether the mortar recipes can be adapted for a better compatibility. In addition, the effect ofglauconite addition in the mortar is studied to resolve the possibility of ageing of the mortar similar to the stone.

Compatibility study and adaption of stone repair mortars for the Lede stone (Belgium)

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Compatibility study and adaption of stone repair mortars for the Lede stone (Belgium)

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