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Title: Inhibition of ASR and DEF: evaluation of the microstructure of concrete mixes with pozzolanic additions
Authors: Santos Silva, A.
Soares, D.
Matos, L.
Divet, L.
Salta, M. M.
Keywords: Asr;Def;Scanning electron microscopy;Microstructure;Pozzolanic additions
Issue Date: Jun-2011
Publisher: ZAG, Slovenian National Building and Civil Engineering Institute
Citation: Proceedings of 13th Euroseminar on Microscopy Applied to Building Materials
Abstract: The use of pozzolanic mineral additions is a known method to inhibit the expansive chemical reactions in concrete, like the alkali-silica reaction (ASR) or the delayed ettringite formation (DEF). The ASR is a chemical reaction that occurs between certain types of minerals present in aggregates and alkali and hydroxyl ions present in the interstitial solution of cement paste in concrete. This reaction involve the dissolution of amorphous or poorly crystallized forms of silica, in alkaline medium, with the formation of an alkaline hygroscopic gel that absorbs water and expands, creating internal stresses in the concrete with cracking. The DEF is a pathology related with the formation of expansive ettringite due to an excessive heating of the concrete during the cure that induces swelling, cracking and decrease of the mechanical properties of the hardened concrete. This paper presents the results of SEM/EDS analysis of concrete mixes with different pozzolanic materials, like metakaolin, biomass fly ash, natural pozzolan and mine sludge from a tungsten mine. The microstructural evaluation is discussed and correlated with the expansion data of each concrete mix.
ISBN: 978-961-90366-7-9
Appears in Collections:DM/NMM - Comunicações a congressos e artigos de revista

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