Browsing by Author "Cultrone, Giuseppe"

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    Characterization and damage assessment of stones used in the Pasargadae World Heritage Site, Achaemenian period
    (2019) Shekofteh, Atefeh; Molina, Eduardo; Arizzi, Anna; Cultrone, Giuseppe; Ahmadi, Hossein; Yazdi, Mehdi
    The architectural remains at Pasargadae were built of three different stones classified according to their colors (beige, dark-gray, and green-gray). The stones show different macroscopic features, such as texture and decay patterns. The aim of this study is to identify the composition of the stones and to evaluate the main decay factors through petrographic studies in order to make conservation decisions more compatible. Petrochemical analyses show that the stones are in fact limestones with different features; two of them have a compact texture (beige and dark-gray stones), while the third has a fairly porous structure (green-gray stone). In some beige stone samples, dolomite was identified. Despite the fact that the presence of salt is a possible decay factor, X-ray diffraction analysis did not report any salt. According to SEM observations, the main reasons for decay in dark-gray and green-gray stones are the dissolution of calcite crystals and the swelling of clay minerals. The main decay factor in the beige stone, by contrast, is dissolution induced by microorganism activity. However, a patina formed by lichens on the surface of the beige stone, although aesthetically detrimental, protects it against further decay.
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    Gypsum crust as a source of calcium for the consolidation of carbonate stones using a calcium phosphate-based consolidant
    (ELSEVIER SCI LTD, 2017) Molina, Eduardo; Rueda Quero, Lucia; Benavente, David; Burgos Cara, Alejandro; Ruiz Agudo, Encarnacion; Cultrone, Giuseppe
    The high levels of atmospheric pollution in cities today are causing the decay of natural building stone, especially due to the formation of gypsum crusts on carbonate stones. For this reason we have assessed the efficacy of using the gypsum crust as an alternative source of calcium in the consolidation of building stone via the formation of calcium phosphates. Samples of Arenisca Ronda (southern Spain) were altered to develop a gypsum crust on the surface for subsequent application of a cellulose poultice with a solution of dibasic ammonium phosphate 3 M (DAP) at different application times. The best results were obtained by the samples treated for 60 min and they have indicated that the application time and the water saturation degree of the poultice affect the amount of gypsum removed and the quantity of fissures on the consolidant film. On the other hand, the DAP concentration of the solution and the pH controlled the calcium phosphate precipitation phases. The habit of the calcium phosphate crystals evolve over the time tending to a homogenization of the consolidant film. This procedure offers an important alternative for the treatment of altered carbonate stones, in which the stone can be cleaned and consolidated in a single application. (C) 2017 Elsevier Ltd. All rights reserved.