A through solution mechanism for delayed ettringite formation in pre-existing cracks in Portland cement mortar

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TypeArticle
Journal titleJournal of Materials Science Letters
ISSN0261-8028
Volume14
Pages217219; # of pages: 3
SubjectCement and Concrete; Mortar; Concrete
AbstractIt has been reported that nucleation of ettringite crystals in cement pastes will preferentially occur incrack tip-zones rather than on plane solid surfaces in a cement-based matrix under conditions of supersaturation. This explanation of the phenomena is compatible with results from many case studieswhere ettringite was usually found in cracks. Recent research reported by Scrivener and Tayloralso confirmed this phenomenon. It was believed that high-temperature steam curing followed byhigh-temperature drying to form microcracks was an optimum condition for concrete deterioration due tosecondary ettringite formation. Two different arguments were discussed for interpretation of ettringite-related expansion mechanisms for Portland cement concrete; the crystal growth theory and the swelling theory. Cohen postulated that expansion results from the growth of ettringite crystals formed on the surfaces of the AI-bearing particles. The growth of these crystals results in crystallization pressure and expansion occurs. Mehta argued that expansion is attributed to the swelling of colloidal particles of ettringite. The formation of this swelling gel occurs by a through solution mechanism. Expansion could occur either by intercalation or surface adsorption effects. The phenomenon of preferred nucleation of secondary ettringite in pre-existing cracks appears to support arguments for a through-solution deposition mechanism. Resulting expansion likely occurs through crystal growth in conforming with Cohen's postulation.
Publication date
LanguageEnglish
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedYes
IdentifierIRC-P-3719
NRC number37873
5233
NPARC number20375861
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Record identifier131a4e23-dc40-4a80-8b5d-f276147347b1
Record created2012-07-23
Record modified2016-05-09
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