Conservation and Restoration of Cultural Heritage / Kültür Varlıklarını Koruma ve Onarım

Permanent URI for this collectionhttps://hdl.handle.net/11147/23

Browse

Filters

2002 - 20032

Settings

End date: 2009Subject: search.filters.subject.Gypsum

Search Results

Now showing 1 - 2 of 2
  • Article
    Citation - WoS: 8
    Citation - Scopus: 8
    Reducing Marble-So2 Reaction Rate by the Application of Certain Surfactants
    (Springer Verlag, 2003) Böke, Hasan; Gauri, K. Lal
    Sulfur dioxide (SO2), prevalent in the modern urban environment of industrial countries, attacks calcite (CaCO3) in marble. As a result, a gypsum (CaSO4.2H2O) crust is produced at rain-sheltered surfaces while areas exposed to rain experience accelerated erosion. We have investigated the effect of certain surfactants as protective agents against SO2 attack. We report that the anions oxalate (C2O4-2) and oleate (C17H33COO-) from solutions of their highly soluble alkali salt species are able to replace carbonate (CO3-2) in calcite producing less reactive substrate of oxalate and oleate of calcium. Experiments to measure the protection obtained by these treatments were carried out in the laboratory and field conditions at nearly 1 ppm and 10 ppb SO2 concentrations, respectively. We found that these treatments provided significant protection to marble exposed in sheltered areas, up to 30% reduction of reaction rate by treatment with 2 × 10-4 M sodium oleate and up to 14% by a 2 × 10-3 M with potassium oxalate solutions, but become ineffective over long term exposure when applied to surfaces exposed to rain. Carrara marble was used in the reported study. Ion chromatography was the analytical tool, which allowed precise measurements of ionic concentrations of these salts, the amount of their uptake by marble, and the thickness of the gypsum crust. X-ray diffraction allowed determination of the new minerals formed at the marble surface by the treatment with surfactants.
  • Article
    Citation - WoS: 22
    Citation - Scopus: 23
    Effect of Some Surfactants on So2-Marble Reaction
    (Elsevier Ltd., 2002) Böke, Hasan; Göktürk, E. Hale; Caner Saltık, Emine N.
    In the polluted atmosphere, sulphur dioxide (SO2) reacts with calcite (CaCO3) in marble producing calcium sulphite hemihydrate (CaSO3·0.5 H2O) and gypsum (CaSO4·2H2O). Gypsum develops crust at rain-sheltered surfaces and then, being more soluble, accelerates erosion at areas exposed to rain. Eventually, all these lead to significant deformations in the appearance and structure of marble surfaces. Clearly, some precautions must be taken to stop or at least to slow down this deterioration process which destroys our cultural heritage. In this study, we have investigated the possibilities of preventing the SO2-marble reaction by using water-soluble surfactants: Abil Quat 3270 and Tween 20. Experiments for measuring their effects have been carried out at conditions simulating the dry deposition of SO2. Infrared spectrometry and scanning electron microscopy were used to analyze the mineralogical composition and morphology of the reaction products. The extent of sulphation reaction was calculated by determining calcium sulphite hemihydrate and gypsum quantitatively by an IR approach and also by weight increases observed during the progress of SO2-marble reaction. A 10% decrease is observed in the total sulphation with both surfactant applications. The results have been discussed in relation to the possible stages of sulphation reaction and surface reactions of calcite.