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Survey of salinity of masonry under III. courtyard at Prague Castle
Slížková, Zuzana ; Ševčík, Radek ; Viani, Alberto ; Mácová, Petra
Archaeological architectural monuments in the area under III. in the courtyard of Prague Castle were monitored in 2021 in terms of the extent of salt efflorescences and their chemical composition. Salt efflorescence on the marlstone walls of the church of St. Bartholomew contain sodium carbonate and bicarbonate, sodium sulfate and calcium sulfate. Sodium nitrate and potassium nitrate were also present in some samples. The aim of the research is to propose measures to mitigate the effect of salts on the degradation of historic masonry.
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Quantification of microstructural changes in limestone cement paste stored in sulfate environment at low temperature
Sotiriadis, Konstantinos ; Hlobil, Michal ; Machová, Dita ; Mácová, Petra ; Viani, Alberto ; Vopálenský, Michal
Samples of cement paste based on mixed cement with limestone admixture were stored in a magnesium sulfate solution for 6 months at 5 ° C to monitor the development of sulfate corrosion and its effect on microstructure. The extent of corrosion was evaluated by several different techniques. The paste samples were scanned at monthly intervals by X-ray tomography for non-destructive quantification of the pore structure and extent of damage, along with a description of the phase changes in the microstructure using X-ray diffraction and infrared spectroscopy. Compressive strength testing confirmed the effect of corrosion on the mechanical resistance of the samples. The results show a rapid course of degradation propagating in an irregular band, caused primarily by the formation of expandable sulfur-based corrosion products, the consequent crack formation and loss of internal cohesion of the material. The occurrence of both ettringite and thaumasite and gypsum was confirmed in the damaged parts.
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