Characterization and damage of the historic brick masonry of the Zákupy castle stables

Abstract

Abstract A chemical-mineralogical analysis and mechanical tests of historical bricks were carried out as part of the construction-technical survey. The objective was to identify the causes of significant masonry decay. The ruined agricultural yard is a national cultural monument. Conservators believe that the historical importance exceeds that of the neighbouring castle. Stables were designed in 1650 by prominent Italian builders Giulio Broggio and Giovanni Domenico Orsi. The building has not been maintained since the conclusion of World War I. After removal from the masonry, the analyzed samples of bricks reached a very high, almost total degree of water saturation - 87-94%. Some bricks are heavily contaminated with nitrates and sulfates, infrared spectrometry analysis showed that calcium nitrate tetrahydrate is the most abundant of the nitrates. The determined average values of physical properties (bulk weight 1764 kg/m3, capillary absorption 13.6% by weight and open porosity 24% by volume) from samples under atmospheric pressure are comparable to the values of masonry bricks produced today. The results of the tests on the bricks from the Zákupy Castle stables construction demonstrate the high manufacturing quality of the masonry elements utilized. Based on the results of the analyses, it can be assumed that three degradation factors contribute to the observed damage to the bricks: high wetting of the masonry (almost total saturation of pores with water), which is most likely long-term lasting, frost cycles - repeated freezing and thawing of water in the bricks during the winter months, and repeated crystallization of water-soluble salts present in pores near the surface.