Modelling of guest-ion incorporation in the anhydrous calcium silicate phases of Portland cement by periodic Density Functional Theory calculations

Activity: Talk or presentation typesLecture and oral contribution

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Jørgen Skibsted - Lecturer

  • Interdisciplinary Nanoscience Center
  • Department of Chemistry
 The potential of periodic density functional theor (DFT) calculations to predict site preferences and substitution schemes for the incorporation of guest ions in alite (Ca3SiO5) and belite (β-Ca2SiO4) is investigated. This includes the setup of a calculation approach that provides information about the coupled substitution of Si4+ and O2- by either Al3+, F- or B3+ , F- ions. For the incorporation of Al3+ and F-  in alite, it is found that the fluoride ions preferentially replace the interstitital oxygen sites which is in full agreement with a recent 29Si{19F} NMR study. For the coupled B3+ - F- incorporation  it is found that fluoride replaces a covalently bonded oxygen in the borate unit and that the tetrahedral enviroonment is transformed in to a trigonal BO3 unit with F...BO3 contacts in the range 2.35 - 2.50 Å. Finally, a preliminary DFT study of the interaction between a water molecule and the surface of alite is reported. These calculations show a significantly lower energy for the reaction of H2O with the interstitial oxygen sites as compared to the covalently bonded oxygens of the SiO4 tetrahedra. Thus, H2O donates H+ to the interstitial oxygen while the remaining hydroxyl group is ionically bonded to the Ca2+ ions at the surface.
Emneord: Periodic DFT calculations, guest-ion incorporation, alite and belite, hydroxylation reactions
22 Jun 201025 Jun 2010

Event (Conference)

TitleLecture, CONMOD 2010: 3rd RILEM Conference on Concrete Modelling
Date22/06/2010 → …
CityLausanne
CountrySwitzerland

    Keywords

  • Periodic DFT calculations, guest-ion incorporation, alite and belite, hydroxylation reactions

ID: 20994116