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The kinetics of ettringite formation and dilatation in a blended cement with beta-hemihydrate and anhydrite as calcium sulfate

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Author

Summary, in English

The phase formation, heat of hydration and dilatation in a blended cement consisting of 50 wt.% calcium aluminate cement, 25 wt.% Portland cement and 25 wt.% calcium sulfate were studied (w/c= 1). The calcium sulfate was beta-hemilrydrate, anhydrite and mixes of the two. Kinetic expressions describing the ettringite formation in the pastes with the pure calcium sulfates were found. Hydration reactions were suggested and the phase development was compared to the hydration heat by mass and heat balances. When the calcium sulfate was 75 and 50 wt.% beta-hemihydrate, the systems behaved as a linear combination of the 100 and 0 wt.% blends. At 25 wt.%, the hydration kinetics differed from the other blends. With only beta-hemihydrate, the last 50% of ettringite formation was accompanied by expansion, mainly caused by interaction of crystals growing radially on cement grains. In the paste with only anhydrite, ettringite crystals grew in solution and produced no expansion.

Publishing year

2005

Language

English

Pages

2310-2321

Publication/Series

Cement and Concrete Research

Volume

35

Issue

12

Document type

Journal article

Publisher

Elsevier

Topic

  • Chemical Sciences

Keywords

  • ettringite
  • expansion
  • thermodynamic calculations
  • hydration
  • kinetics

Status

Published

ISBN/ISSN/Other

  • ISSN: 0008-8846