|Autor||De Clercq, H. and Godts, S.|
|Titel||Salt extractions of brickwork: a standard procedure?|
|Link||Datei:32 SWBSS-2014 De Clercq etal.pdf|
|Bemerkungen||In: De Clercq, Hilde (editor): Proceedings of SWBSS 2014. Third International Conference on Salt Weathering of Buildings and Stone Sculptures Royal Institute for Cultural Heritage, Brussels, Belgium, 14-16 October 2049, S. 457-467|
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brickwork, salt extraction, poultic
Crystallization of salts is recognized as a major factor in the degradation of porous materials in built heritage. Salt damage occurs in the presence of salts and moisture, in liquid or vapour form. This implies that, in case one of both can be excluded, salt damage can be mitigated. A salt extraction aims to reduce a maximum amount of salts present. In practice salt extractions are often executed without scientific background or control of its effect or durability.This paper deals with the results of salt extractions using a poultice consisting of a mixture of kaolin, sand and cellulose fibers applied on salt contaminated brickwork of two cases, the abandoned coal mine site named C-mine in Winterslag and two chapels of the Cathedral of Our Lady in Antwerp. Results have shown that several factors influence the salt extraction effect: the amount and distribution of salts, the pre-wetting properties, the physical properties of the building materials as well as the environmental conditions of the salt extraction execution. From the experimentally determined salt contamination and distribution as well as the properties of the poultice and the building materials of the masonry, the salt extraction execution parameters and its effect were first approached theoretically through modelling. The predicted effect was compared to the one experimentally determined. Concerning the last, powder drill samples were lifted from brick and mortar, before and after each salt extraction from which the ion content was determined quantitatively. From the results it was concluded that the optimum conditions for the execution of a salt extraction cannot be considered as a standard copy-paste application suitable for all types of salt contaminated brickwork. A critical note is to be tackled with respect to the term salt extraction as the reality shows that an important part of the salts migrate deeper into the brickwork.