Hydration kinetics of tricalcium silicate: A dataset for reaction rate calculations and nanoscale analysis employing atom probe tomography
Naber C (2019)
Publication Language: English
Publication Type: Thesis
Publication year: 2019
URI: https://opus4.kobv.de/opus4-fau/frontdoor/index/index/docId/10335
Abstract
- The hydration of tricalcium silicate (C3S) is a dissolution precipitation process. The dissolution of C3S delivers ions to the pore solution and the hydration products Calcium-Silicate-Hydrate (C-S-H) and portlandite (CH) consume said ions by precipitating from the pore solution. The underlying kinetics of the coupled reaction are to this day not fully understood. This thesis presents efforts to investigate the C3S - water interface at the nanoscale and a comprehensive dataset to calculate individual C3S dissolution rates and C-S-H precipitation rates during hydration.
The C3S - water interface is investigated in this work by atom probe tomography (APT), an imaging technique with three-dimensional nanoscale resolution and chemical identification. In order to obtain samples suitable for APT, a method to synthesize large monocrystalline C3S grains is presented. The synthesis is conducted in an optical floating zone furnace by annealing polycrystalline rods at temperatures just below the melting point of C3S. Large monocrystalline grains (>500 µm) of monoclinic and triclinic polymorphs of C3S could be synthesized. The atom probe tomography experiments conducted with the thus produced samples demonstrate that it is possible to measure tricalcium silicate with this method by carefully adjusting the measurement parameters. Furthermore it could be shown that the sample preparation and measurement conditions employed are harmful to the hydrate phase C-S-H and thus also to potential metastable reaction products forming at the C3S - water interface. These harmful conditions might be avoided by applying a novel sample preparation procedure at cryo conditions.
The presented comprehensive dataset contains data for the first 24 hours of hydration of triclinic and monoclinc C3S samples at different water to solid ratios. The measured parameters include XRD and NMR phase contents, pore solution concentrations, specific surface areas, and SEM images at various time steps. With this dataset, it is possible to calculate theoretical C3S dissolution and C-S-H precipitation rates by combination with interfacial dissolution and precipitation rates determined separately. The results show a good fit between the theoretical C-S-H precipitation rates and the actual reaction rates measured for both C3S polymorphs and all investigated water to solid ratios indicating that the applied calculation model incorporates all relevant factors to describe C-S-H precipitation kinetics during C3S hydration. The theoretical C3S dissolution rates in contrast do not fit the actual reaction rates in all investigated systems. This demonstrates that there are important factors missing in the applied calculation model for C3S dissolution kinetics.
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How to cite
APA:
Naber, C. (2019). Hydration kinetics of tricalcium silicate: A dataset for reaction rate calculations and nanoscale analysis employing atom probe tomography (Dissertation).
MLA:
Naber, Christoph. Hydration kinetics of tricalcium silicate: A dataset for reaction rate calculations and nanoscale analysis employing atom probe tomography. Dissertation, 2019.
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