Ettringite and thaumasite: A chemical route for their removal from cementious artefacts |
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| Authors: | Enrico Ciliberto Salvatore Ioppolo Fabio Manuella |
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| Institution: | aDipartimento di Scienze Chimiche, Università degli Studi di Catania, viale A. Doria 6, 95125 Catania, Italy;bDipartimento di Scienze Geologiche, Università degli Studi di Catania, Sezione di Mineralogia, Petrografia, Geochimica e Vulcanologia, C.so Italia 57, 95129 Catania, Italy |
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| Abstract: | 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. |
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| Keywords: | Ettringite Thaumasite Synthesis Barium hydroxide Portland cement Cathedral Nicosia Sicily |
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