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TitleThe effect of sulfate activation on the early age hydration of BFS:PC composite cement
Publication TypeJournal Article
Year of Publication2015
AuthorsCollier, N.C., Li X., Bai Y., and Milestone N.B.
JournalJournal of Nuclear Materials
Pagination128 - 134
Date Published2015
ISSN00223115 (ISSN)
KeywordsBlast furnaces, Calcium, Cement composite, Cement replacement, Cements, Chemical activation, Composite cements, Corrosion, Early age hydrations, Hydration, Hydration products, Intermediate level, Neutral salts, Portland cement, Radioactive wastes, Reactive metals, Slags, Sodium sulfate, Sulfur compounds
AbstractBlast furnace slag/Portland cement composites are routinely used for immobilising intermediate level nuclear wastes in the UK. Using high cement replacement levels reduces hydration exotherm and lowers pH. Although a lower grout pH will be beneficial in reducing the corrosion of certain encapsulated reactive metals such as aluminium, the degree of slag reaction will also be lower which may result in the formation of less hydration products and which in turn may reduce the capacity to immobilise waste ions. Adding neutral salts such as calcium and sodium sulfate to the composite cement can potentially increase slag activation without significantly altering the pH of the cement matrix. Thus the corrosion of any encapsulated metals would not be affected. This paper describes some of the properties of a hydrated 9:1 blast furnace slag:Portland cement matrix containing added sulfates of calcium and sodium. The findings show that all additives caused an increase in the amount of slag that reacted when cured for up to 28 days. This produced more material able to chemically bind waste ions. Activation with gypsum produced the highest rate of slag reaction. © 2015 Elsevier B.V. All rights reserved.

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