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Physical and mechanical properties of the repaired sandstone ashlars in the facing masonry of the Charles Bridge in Prague (Czech Republic) and an analytical study for the causes of its rapid decay
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SYSNO ASEP 0364644 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Physical and mechanical properties of the repaired sandstone ashlars in the facing masonry of the Charles Bridge in Prague (Czech Republic) and an analytical study for the causes of its rapid decay Author(s) Přikryl, R. (CZ)
Weishauptová, Zuzana (USMH-B) RID, ORCID
Novotná, M. (CZ)
Přikrylová, J. (CZ)
Šťastná, A. (CZ)Source Title Environmental Earth Sciences. - : Springer - ISSN 1866-6280
Roč. 63, 7/8 (2011), s. 1623-1639Number of pages 17 s. Publication form www - www Language eng - English Country DE - Germany Keywords natural stone ; weathering ; water soluble salts Subject RIV AL - Art, Architecture, Cultural Heritage R&D Projects GA205/08/0676 GA ČR - Czech Science Foundation (CSF) CEZ AV0Z30460519 - USMH-B (2005-2011) UT WOS 000292744300016 DOI 10.1007/s12665-010-0819-5 Annotation The facing masonry of the Gothic Charles Bridge in Prague (Czech Republic) has been largely altered during nineteenth and twentieth century repairs, due to extensive replacements of weathered sandstone ashlar blocks. Natural stone varieties used during these replacements show different responses to a variety of weathering processes which lead to their rapid decay. The decay of the newer stone has been accelerated by use of Portland cement paste as the binding and fill material, instead of the original hydraulic lime-based and cocciopesto-type mortars. The hardened Portland cement paste makes an almost impermeable barrier, with permeability three to four orders of magnitude lower, compared to the original mortars and natural stone. The low permeability of this new alien material results in the accumulation of water-soluble salts (specifically nitrates, but also sulphates and chlorides) in the facing masonry ashlars, with their crystallisation coming in the form of both sub- and efflorescence, as well as the development of various decay forms (blistering, granular disintegration and/or scaling and flaking). The source of the water-soluble salts can be traced back to previous restoration attempts. These included chemical cleaning (black crust removal) by nitric acid, ammonium hydroxide (‘ammonium water’), or ammonium hydrogen carbonate, all which can be linked to high nitrate content in the efflorescence. Workplace Institute of Rock Structure and Mechanics Contact Iva Švihálková, svihalkova@irsm.cas.cz, Tel.: 266 009 216 Year of Publishing 2012
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