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

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Abstract

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.
Original languageEnglish
Pages (from-to)2310-2321
JournalCement and Concrete Research
Volume35
Issue number12
DOIs
Publication statusPublished - 2005

Bibliographical note

The information about affiliations in this record was updated in December 2015.
The record was previously connected to the following departments: Polymer and Materials Chemistry (LTH) (011001041)

Subject classification (UKÄ)

  • Chemical Sciences

Keywords

  • ettringite
  • expansion
  • thermodynamic calculations
  • hydration
  • kinetics

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