Ettringite Formation in Dam Gallery


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Title: Ettringite Formation in Dam Gallery

Author(s): R. A. Kennerley

Publication: Journal Proceedings

Volume: 62

Issue: 5

Appears on pages(s): 559-576

Keywords: calcium sulfoaluminate, concrete, dam, efflorescence, ettringite, fly ash, prepacked concrete, sulfate.

Date: 5/1/1965

The formation of a deposit of ettringite in a submerged dam gallery is described. It occurred in an area where a fly ash-cement mixture had been used for the placement of pre-packed concrete. Where fly ash was used to replace a portion of the cement in conventionally placed concrete nearby, no such deposit was observed. No evidence of deterioration of the concrete could be found. It is believed that water seeping along permeable planes in the concrete dissolved some of the sulfate and alumina-containing phases formed during cement hydration and, on reaching the gallery, ettringit tew asprecipitated from the solution. The deposit was found adjacent to a stop-work plane in the grouting of the aggregates, and it is thought that the concrete at this point could have become enriched in lighter hydration products (e.g., calcium sulfoaluminate, calcium hydroxide) and grout admixtures. The formation of ettringite as a stable product of cement hydration would have been assisted by additional sulfate derived from the fly ash.