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

Sassoni, Enrico ; Graziani, Gabriela ; Scherer, George W. ; Franzoni, Elisa (2016) Preliminary study on the use of ammonium phosphate for the conservation of marble-imitating gypsum-stuccoes. DOI 10.6092/unibo/amsacta/5705. In: Proceedings of the 4th Historic Mortars Conference HMC2016 10th-12th October 2016, Santorini, Greece. A cura di: Papayianni, Ioanna ; Stefanidou, Maria ; Pachta, Vasiliki. pp. 391-398. ISBN 978-960-99922-3-7.
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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.

Document type
Book Section
Sassoni, EnricoUniversity of Bologna,
Graziani, GabrielaUniversity of Bologna, Italy
Scherer, George W.Princeton University, USA
Franzoni, ElisaUniversity of Bologna, Italy
Gypsum; Hydroxyapatite; Marble; Protection; Consolidation; Cultural Heritage
Deposit date
18 Oct 2017 07:53
Last modified
18 Oct 2017 07:53
Project name
HAP4MARBLE - Multi-functionalization of hydroxyapatite for restoration and preventive conservation of marble artworks
Funding program
EC - H2020

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