In this study, a novel method for consolidation and improvement of resistance to water of gypsum-stuccoes was preliminarily investigated. The idea is treating gypsum with an aqueous solution of diammonium hydrogen phosphate (DAP, (NH4)2HPO4) to form hydroxyapatite (HAP, Ca10(PO4)6(OH)2), which has much lower solubility than gypsum. Tests carried out on gypsum paste samples, manufactured to resemble historic stuccoes, showed that, after treatment with the DAP solution, a significant improvement in mechanical properties was achieved and brushite (CaHPO4∙2H2O) was formed (alongside some other by-products, that can be removed by an additional poultice treatment). Even if brushite is more soluble than HAP, still its formation is expected to be beneficial for stuccoes conservation, as brushite is significantly less soluble than gypsum.

Preliminary study on the use of ammonium phosphate for the conservation of marble-imitating gypsum-stuccoes

SASSONI, ENRICO;GRAZIANI, GABRIELA;SCHERER, GEORGE WALTER;FRANZONI, ELISA
2016

Abstract

In this study, a novel method for consolidation and improvement of resistance to water of gypsum-stuccoes was preliminarily investigated. The idea is treating gypsum with an aqueous solution of diammonium hydrogen phosphate (DAP, (NH4)2HPO4) to form hydroxyapatite (HAP, Ca10(PO4)6(OH)2), which has much lower solubility than gypsum. Tests carried out on gypsum paste samples, manufactured to resemble historic stuccoes, showed that, after treatment with the DAP solution, a significant improvement in mechanical properties was achieved and brushite (CaHPO4∙2H2O) was formed (alongside some other by-products, that can be removed by an additional poultice treatment). Even if brushite is more soluble than HAP, still its formation is expected to be beneficial for stuccoes conservation, as brushite is significantly less soluble than gypsum.
Proceedings of the 4th Historic Mortars Conference (HMC2016)
391
398
Enrico Sassoni; Gabriela Graziani; George W. Scherer; Elisa Franzoni
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/598206
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