engleski

Efficiency of using calcium oxalate for protection of monumental limestone and marble

Limestone and marble are common types of stone materials used in construction of buildings and monuments. At the outside environment they undergo wet weathering which degrades the stone substrate. For the protection of outdoor monuments, an alternative to the use of hydrophobic compounds is to use acid resistant passivating agents like calcium oxalate (CaOx). We investigated the efficiency of several treatment procedures using synchrotron based scanning micro-XRF measurements to visualize CaOx surface coverage distributions on treated surfaces. Treated stone surfaces were exposed to 2% sulphuric acid. At the places where CaOx has not been formed, gypsum is created. Then synchrotron induced micro-XRF analysis can be used to visualize at the range of few cm2 the formation of CaOx on the CaCO3 base by mapping the presence of sulphur over the treated surface. In order to avoid interference phenomena in S-K detection, such as increased background and secondary fluorescence induced by the strong Ca-K fluorescence peaks, the exciting X-ray energy was selected below the Ca K edge. Measurements were performed at the XRF beam-line of Elettra Sincrotrone Trieste equipped with a multipurpose X-ray spectrometry end-station. The results obtained have been compared with corresponding micro-PIXE results and those obtained earlier.

micro-XRF ; calcioum oxalate ; limestone ; marble ; protection

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