Thermodynamic modeling of hydrated white Portland cement–metakaolin–limestone blends utilizing hydration kinetics from 29Si MAS NMR spectroscopy |
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| Affiliation: | 1. Laboratory of Construction Materials, École Polytechnique Fédérale de Lausanne (EPFL), Station 12, CH-1015 Lausanne, Switzerland;2. HeidelbergCement Technology Center GmbH (HeidelbergCement AG), Rohrbacher Str. 95, 69181 Leimen, Germany;1. Department of Civil and Environmental Engineering, Francis College of Engineering, University of Massachusetts Lowell, Lowell, MA 01854, USA;2. Sonny Astani Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, CA 90089, USA;1. Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, 8000 C Aarhus, Denmark;2. Laboratory for Concrete & Construction Chemistry, Swiss Federal Laboratories for Materials Science and Technology (Empa), 8600 Dübendorf, Switzerland;3. Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), Trondheim 7491, Norway;4. Aalborg Portland A/S, Cementir Holding S.p.A., 9100 Aalborg, Denmark;1. Department of Chemistry and Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C, Denmark;2. Department of Structural Engineering, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway;3. SINTEF Building and Infrastructure, 7491 Trondheim, Norway;4. Laboratory for Concrete & Construction Chemistry, Swiss Federal Laboratories for Materials Science and Technology (Empa), 8600 Dübendorf, Switzerland |
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| Abstract: | Hydration kinetics for the principal phases of Portland cement blends have been incorporated in thermodynamic modeling (GEMS package), utilizing degrees of hydration from 29Si MAS NMR. An empirical relationship for the reaction of these phases is established which includes three variable parameters that all can be estimated from the degrees of hydration. This approach is compared with thermodynamic equilibrium modeling (full hydration) for white Portland cement–metakaolin (0–30 wt.%) blends and for ternary blends of white Portland cement (65 wt.%)–metakaolin–limestone. The predicted phase assemblages have been compared with the phases identified by XRD, 27Al and 29Si MAS NMR which reveals that the incorporation of hydration kinetics improves the agreement between modeling and experiments. The results show also that the formation of strätlingite depends critically on the quantity of charge-balancing anions in the AFm phases, especially carbonate and sulfate anions, and on the degree of hydration for metakaolin. |
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