Temperature dependence, 0 to 40 °C, of the mineralogy of Portland cement paste in the presence of calcium carbonate

Thomas Matschei*, Fredrik P. Glasser

*Corresponding author for this work

Research output: Contribution to journalArticle

42 Citations (Scopus)

Abstract

Thermodynamic calculations disclose that significant changes of the AFm and AFt phases and amount of Ca(OH)2 occur between 0 and 40 °C; the changes are affected by added calcite. Hydrogarnet, C3AH6, is destabilised at low carbonate contents and/or low temperatures < 8 °C and is unlikely to form in calcite-saturated Portland cement compositions cured at < 40 °C. The AFm phase actually consists of several structurally-related compositions which form incomplete solid solutions. The AFt phase is close to its ideal stoichiometry at 25 °C but at low temperatures, < 20 °C, extensive solid solutions occur with CO3-ettringite. A nomenclature scheme is proposed and AFm–AFt phase relations are presented in isothermal sections at 5, 25 and 40 °C. The AFt and AFm phase relations are depicted in terms of competition between OH, CO3and SO4 for anion sites. Diagrams are presented showing how changing temperatures affect the volume of the solid phases with implications for space filling by the paste. Specimen calculations are related to regimes likely to occur in commercial cements and suggestions are made for testing thermal impacts on cement properties by defining four regimes. It is concluded that calculation provides a rapid and effective tool for exploring the response of cement systems to changing composition and temperature and to optimise cement performance.

Original languageEnglish
Pages (from-to)763-777
Number of pages15
JournalCement and Concrete Research
Volume40
Issue number5
DOIs
Publication statusPublished - May 2010

Keywords

  • thermodynamic calculations
  • durability
  • CaCO(3)
  • ettringite
  • monosulfate
  • molal thermodynamic properties
  • solid-solution
  • hydration
  • 25-degrees-C
  • aluminate
  • Crestmore
  • complexes

Cite this

Temperature dependence, 0 to 40 °C, of the mineralogy of Portland cement paste in the presence of calcium carbonate. / Matschei, Thomas; Glasser, Fredrik P.

In: Cement and Concrete Research, Vol. 40, No. 5, 05.2010, p. 763-777.

Research output: Contribution to journalArticle

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AB - Thermodynamic calculations disclose that significant changes of the AFm and AFt phases and amount of Ca(OH)2 occur between 0 and 40 °C; the changes are affected by added calcite. Hydrogarnet, C3AH6, is destabilised at low carbonate contents and/or low temperatures < 8 °C and is unlikely to form in calcite-saturated Portland cement compositions cured at < 40 °C. The AFm phase actually consists of several structurally-related compositions which form incomplete solid solutions. The AFt phase is close to its ideal stoichiometry at 25 °C but at low temperatures, < 20 °C, extensive solid solutions occur with CO3-ettringite. A nomenclature scheme is proposed and AFm–AFt phase relations are presented in isothermal sections at 5, 25 and 40 °C. The AFt and AFm phase relations are depicted in terms of competition between OH, CO3and SO4 for anion sites. Diagrams are presented showing how changing temperatures affect the volume of the solid phases with implications for space filling by the paste. Specimen calculations are related to regimes likely to occur in commercial cements and suggestions are made for testing thermal impacts on cement properties by defining four regimes. It is concluded that calculation provides a rapid and effective tool for exploring the response of cement systems to changing composition and temperature and to optimise cement performance.

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KW - aluminate

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