Ettringite and thaumasite: A chemical route for their removal from cementious artefacts

The present paper reports a new method for converting ettringite and thaumasite in non-expansible and insoluble phases, for its application in the restoration of concrete artefacts subjected to deterioration through sulphate attack. The salts were synthesized by different processes and, after charac...

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Bibliographic Details
Published in:Journal of cultural heritage 2008, Vol.9 (1), p.30-37
Main Authors: Ciliberto, Enrico, Ioppolo, Salvatore, Manuella, Fabio
Format: Article
Language:English
Subjects:
Barium hydroxide
Cathedral
Ettringite
Nicosia
Portland cement
Sicily
Synthesis
Thaumasite
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Summary:The present paper reports a new method for converting ettringite and thaumasite in non-expansible and insoluble phases, for its application in the restoration of concrete artefacts subjected to deterioration through sulphate attack. The salts were synthesized by different processes and, after characterization by means of XRD, FT-IR and optical microscopy, were treated with a series of chemicals in order to induce their decomposition. In particular, different solutions containing barium nitrate, barium hydroxide and ammonium oxalate were used to achieve the complete transformation of both phases in barite, witherite, scarbroite and whewellite. Barium hydroxide seemed to be the most appropriate reactant because the others could give rise to efflorescence within the pores of the mortars by leaving free nitrate or sulphate ions inside the materials. The experimental technique was also tested on two concrete samples collected from the bell-tower of St. Nicholas’ Cathedral in Nicosia (Sicily) with encouraging results.
ISSN:1296-2074
1778-3674
DOI:10.1016/j.culher.2007.05.004