Sacrificial plaster
Sacrificial plaster (also sacrificial layer ) is a colloquial expression for a traditional artisanal process to reduce salt in masonry . The repair mortar with its very high porosity is used to absorb soluble salts. As soon as it is saturated with salt and can no longer fulfill its task, it is replaced by a new plastering. This removal of the plaster is circumscribed by sacrifice .
It is customary to use it in the construction industry and in monument conservation or restoration as surface protection for buildings.
description
Salts are transported in the masonry by moisture to the surface or wall surfaces ( capillaries ) and cause unsightly efflorescence there . In traditional construction, external walls were whitewashed to protect the plaster from environmental influences. Such a lime plaster ( mortar group I ) can contribute to better dehumidification of the wall. Since the dissolved salts are passed through the kapillarwandernde water up to the evaporation surface of the plaster, and crystallize there, the plaster over time loses its diffusion capability , that is, a salt-contaminated lime plaster does not contribute more to dehumidify the masonry in and needs to be replaced.
The durability of the plaster depends on the exposure of the masonry to precipitation or groundwater and can range from a few months to a few years at most. The advantage of this traditional method can be seen in the inexpensive execution and the continuous absorption of the wall salts (therefore sacrificial plaster ). However, the sacrificial plaster had to be renewed annually because of its low abrasion resistance (see disadvantages when using lime ).
In monument preservation, for example, the weathering of sandstone is prevented by using silicone resin slurries.
literature
- Günther Donath: Silicone resin slurries as surface protection for sandstone using the example of St. Bennokirche in Meißen . Fraunhofer IRB Verlag, Stuttgart 2005, ISBN 978-3-8167-6666-7
- Hans H. Reineke & K. Hahn: Benefits and costs of sacrificial layers: Study for d. Federal Minister d. Inside . Specialized Information Center Karlsruhe, Eggenstein-Leopoldshafen 1983 ( in the German National Library )
Individual evidence
- ↑ sacrificial plaster. In: Angela Weyer et al. (Ed.): EwaGlos. European Illustrated Glossary Of Conservation Terms For Wall Paintings And Architectural Surfaces . English Definitions with translations into Bulgarian, Croatian, French, German, Hungarian, Italian, Polish, Romanian, Spanish and Turkish. Michael Imhof, Petersberg 2015, ISBN 978-3-7319-0260-7 , p. 308 ( download ).
- ↑ Publications on the subject of the sacrificial layer in construction