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Morten Daugaard Andersen - One of the best experts on this subject based on the ideXlab platform.
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the effect of alkali ions on the incorporation of aluminum in the calcium silicate hydrate c s h phase resulting from Portland Cement Hydration studied by 29si mas nmr
Journal of the American Ceramic Society, 2013Co-Authors: Jorgen Skibsted, Morten Daugaard AndersenAbstract:The incorporation of aluminum in the calcium–silicate–hydrate (C–S–H) phases formed by Hydration of three different white Portland Cements has been investigated by 29Si MAS NMR. The principal difference between the three Cements is their bulk Al2O3 contents and quantities of alkali (Na+ and K+) ions. 29Si MAS NMR allows indirect detection of tetrahedral Al incorporated in the silicate chains of the C–S–H structure by the resonance from Q2(1Al) sites. Analysis of the relative 29Si NMR intensities for this site, following the Hydration for the three Cements from 0.5 d to 30 weeks, clearly reveals that the alkali ions promote the incorporation of Al in the bridging sites of the dreierketten structure of SiO4 tetrahedra in the C–S–H phase. The increased incorporation of Al in the C–S–H phase with increasing alkali content in the anhydrous Cement is in accord with a proposed substitution mechanism where the charge deficit, obtained by the replaCement of Si4+ by Al3+ ions in the bridging sites, is balanced by adsorption/binding of alkali ions in the interlayer region most likely in the near vicinity of the AlO4 tetrahedra. This result is further supported by similar 29Si MAS NMR experiments performed for the white Portland Cements hydrated in 0.30M NaOH and NaAlO2 solutions.
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characterization of white Portland Cement Hydration and the c s h structure in the presence of sodium aluminate by 27al and 29si mas nmr spectroscopy
Cement and Concrete Research, 2004Co-Authors: Morten Daugaard Andersen, Hans J. Jakobsen, Joergen SkibstedAbstract:Abstract The effects of hydrating a white Portland Cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO2) at 5 and 20 °C are investigated by 27Al and 29Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO2 accelerates the Hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO4/AlO4 tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the Hydration (6 h to 2 years) but increases for higher concentration of the NaAlO2 solution. The average chain lengths of “pure” silicate and SiO4/AlO4 tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO2 reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.
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characterization of white Portland Cement Hydration and the c s h structure in the presence of sodium aluminate by 27al and 29si mas nmr spectroscopy
Cement and Concrete Research, 2004Co-Authors: Morten Daugaard Andersen, Hans J. Jakobsen, Joergen SkibstedAbstract:The effects of hydrating a white Portland Cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the Hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the Hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.
Joergen Skibsted - One of the best experts on this subject based on the ideXlab platform.
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characterization of white Portland Cement Hydration and the c s h structure in the presence of sodium aluminate by 27al and 29si mas nmr spectroscopy
Cement and Concrete Research, 2004Co-Authors: Morten Daugaard Andersen, Hans J. Jakobsen, Joergen SkibstedAbstract:Abstract The effects of hydrating a white Portland Cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO2) at 5 and 20 °C are investigated by 27Al and 29Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO2 accelerates the Hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO4/AlO4 tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the Hydration (6 h to 2 years) but increases for higher concentration of the NaAlO2 solution. The average chain lengths of “pure” silicate and SiO4/AlO4 tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO2 reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.
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characterization of white Portland Cement Hydration and the c s h structure in the presence of sodium aluminate by 27al and 29si mas nmr spectroscopy
Cement and Concrete Research, 2004Co-Authors: Morten Daugaard Andersen, Hans J. Jakobsen, Joergen SkibstedAbstract:The effects of hydrating a white Portland Cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the Hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the Hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.
Jorgen Skibsted - One of the best experts on this subject based on the ideXlab platform.
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resolution of the two aluminum sites in ettringite by 27al mas and mqmas nmr at very high magnetic field 22 3 t
Journal of Physical Chemistry C, 2017Co-Authors: Jorgen Skibsted, Malene Thostrup Pedersen, Julian HolzingerAbstract:Ettringite (Ca6[Al(OH)6]2(SO4)3·26H2O) is the first Hydration product formed during Portland Cement Hydration. 27Al MAS NMR has been used in a wide number of studies to detect and quantify ettringite in hydrated Cement blends by the observation of a single, narrow resonance at 13–14 ppm. This work reports the first observation of resonances from two distinct Al sites in octahedral coordination for ettringite, employing 27Al MAS and MQMAS NMR at an ultrahigh magnetic field (22.3 T). Thereby, the 27Al NMR spectra are in agreement with the most accepted trigonal model for the ettringite structure. 27Al quadrupole coupling parameters and isotropic chemical shifts for the two Al sites are determined from simulations and least-squares optimization of slow-speed 27Al MAS NMR spectra of the satellite transitions. These data reveal that the local environments for the two octahedral Al sites are very similar, in accord with the most recent XRD refinements of the ettringite structure. Finally, the significant improv...
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composition silicate anion structure and morphology of calcium silicate hydrates c s h synthesised by silica lime reaction and by controlled Hydration of tricalcium silicate c3s
Advances in Applied Ceramics, 2015Co-Authors: Tajuelo E Rodriguez, I G Richardson, L Black, E Boehmcourjault, Andre Nonat, Jorgen SkibstedAbstract:The main product of Portland Cement Hydration is C-S-H. Despite constituting more than half of the volume of hydrated pastes and having an important role in strength development, very little is known about the factors that determine its morphology. To investigate the relationship between the chemical composition, silicate anion structure and morphology of C-S-H, samples were synthesised via silica-lime reactions and by the Hydration of C3S under controlled lime concentrations and with/without accelerators. The silicate anion structure of the samples was studied by 29Si magic angle spinning nuclear magnetic resonance spectroscopy and the morphology and chemical composition by TEM and SEM. All samples prepared via silica-lime reactions with bulk Ca/Si up to 1.5 were foil-like. The Hydration of C3S at fixed lime concentration yielded foil-like C-S-H for [CaO] 22 mmol L−1. A relationship between the silicate anion structure and the morphology of C-S-H was found for the...
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the effect of alkali ions on the incorporation of aluminum in the calcium silicate hydrate c s h phase resulting from Portland Cement Hydration studied by 29si mas nmr
Journal of the American Ceramic Society, 2013Co-Authors: Jorgen Skibsted, Morten Daugaard AndersenAbstract:The incorporation of aluminum in the calcium–silicate–hydrate (C–S–H) phases formed by Hydration of three different white Portland Cements has been investigated by 29Si MAS NMR. The principal difference between the three Cements is their bulk Al2O3 contents and quantities of alkali (Na+ and K+) ions. 29Si MAS NMR allows indirect detection of tetrahedral Al incorporated in the silicate chains of the C–S–H structure by the resonance from Q2(1Al) sites. Analysis of the relative 29Si NMR intensities for this site, following the Hydration for the three Cements from 0.5 d to 30 weeks, clearly reveals that the alkali ions promote the incorporation of Al in the bridging sites of the dreierketten structure of SiO4 tetrahedra in the C–S–H phase. The increased incorporation of Al in the C–S–H phase with increasing alkali content in the anhydrous Cement is in accord with a proposed substitution mechanism where the charge deficit, obtained by the replaCement of Si4+ by Al3+ ions in the bridging sites, is balanced by adsorption/binding of alkali ions in the interlayer region most likely in the near vicinity of the AlO4 tetrahedra. This result is further supported by similar 29Si MAS NMR experiments performed for the white Portland Cements hydrated in 0.30M NaOH and NaAlO2 solutions.
Hans J. Jakobsen - One of the best experts on this subject based on the ideXlab platform.
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characterization of white Portland Cement Hydration and the c s h structure in the presence of sodium aluminate by 27al and 29si mas nmr spectroscopy
Cement and Concrete Research, 2004Co-Authors: Morten Daugaard Andersen, Hans J. Jakobsen, Joergen SkibstedAbstract:Abstract The effects of hydrating a white Portland Cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO2) at 5 and 20 °C are investigated by 27Al and 29Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO2 accelerates the Hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO4/AlO4 tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the Hydration (6 h to 2 years) but increases for higher concentration of the NaAlO2 solution. The average chain lengths of “pure” silicate and SiO4/AlO4 tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO2 reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.
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characterization of white Portland Cement Hydration and the c s h structure in the presence of sodium aluminate by 27al and 29si mas nmr spectroscopy
Cement and Concrete Research, 2004Co-Authors: Morten Daugaard Andersen, Hans J. Jakobsen, Joergen SkibstedAbstract:The effects of hydrating a white Portland Cement (wPc) in 0.30 and 0.50 M solutions of sodium aluminate (NaAlO{sub 2}) at 5 and 20 deg. C are investigated by {sup 27}Al and {sup 29}Si magic-angle spinning (MAS) NMR spectroscopy. It is demonstrated that NaAlO{sub 2} accelerates the Hydration of alite and belite and results in calcium-silicate-hydrate (C-S-H) phases with longer average chain lengths of SiO{sub 4}/AlO{sub 4} tetrahedra. The C-S-H phases are investigated in detail and it is shown that the Al/Si ratio for the chains of tetrahedra is quite constant during the time studied for the Hydration (6 h to 2 years) but increases for higher concentration of the NaAlO{sub 2} solution. The average chain lengths of 'pure' silicate and SiO{sub 4}/AlO{sub 4} tetrahedra demonstrate that Al acts as a linker for the silicate chains, thereby producing aluminosilicate chains with longer average chain lengths. Finally, it is shown that NaAlO{sub 2} reduces the quantity of ettringite and results in larger quantities of monosulfate and a calcium aluminate hydrate phase.
Elhadj Kadri - One of the best experts on this subject based on the ideXlab platform.
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influence of metakaolin and silica fume on the heat of Hydration and compressive strength development of mortar
Applied Clay Science, 2011Co-Authors: Elhadj Kadri, Said Kenai, Karim Ezziane, Rafa Siddique, Gee De SchutteAbstract:article i nfo In this study, two metakaolins (MK1 & MK2) were investigated for use as supplementary Cementitious materials in Cement-based systems. The MK vary in their surface area (17 to 19 m 2 /g), but are almost similar in chemical composition. Total of four series of mortar mixes were made. First was control mix. Second and third mixes contained 10% of each of the MK as partial replaCement of Cement. In fourth mix, Cement was replaced with 10% silica fume (SF). Water-to-Cementitious materials ratio was kept constant as 0.36. Performances of MK mixes were compared with control mix, and mixes incorporating SF. Tests were conducted for early-age properties of fresh mortar and compressive strength. Early age investigation was aimed to determine the reactivity (temperature and heat of Hydration of MK), and its effect on fresh mixture (slump flow). Test results have indicated that (i) blended mortar with MK can reach higher temperature with respect to 100% ordinary Portland Cement; (ii) MK exhibits lower pozzolanic activity than SF. Hydration heat of SF is greater than that of MK; (iii) it is supposed that there are three elementary factors which influence the contribution that MK makes to mortar strength when it partially replaces Cement in mortar. These are the filler effect, the acceleration of ordinary Portland Cement Hydration and the pozzolanic reaction of MK with calcium hydroxide.
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influence of metakaolin and silica fume on the heat of Hydration and compressive strength development of mortar
Applied Clay Science, 2011Co-Authors: Elhadj Kadri, Said Kenai, Karim Ezziane, Rafat Siddique, Geert De SchutterAbstract:article i nfo In this study, two metakaolins (MK1 & MK2) were investigated for use as supplementary Cementitious materials in Cement-based systems. The MK vary in their surface area (17 to 19 m 2 /g), but are almost similar in chemical composition. Total of four series of mortar mixes were made. First was control mix. Second and third mixes contained 10% of each of the MK as partial replaCement of Cement. In fourth mix, Cement was replaced with 10% silica fume (SF). Water-to-Cementitious materials ratio was kept constant as 0.36. Performances of MK mixes were compared with control mix, and mixes incorporating SF. Tests were conducted for early-age properties of fresh mortar and compressive strength. Early age investigation was aimed to determine the reactivity (temperature and heat of Hydration of MK), and its effect on fresh mixture (slump flow). Test results have indicated that (i) blended mortar with MK can reach higher temperature with respect to 100% ordinary Portland Cement; (ii) MK exhibits lower pozzolanic activity than SF. Hydration heat of SF is greater than that of MK; (iii) it is supposed that there are three elementary factors which influence the contribution that MK makes to mortar strength when it partially replaces Cement in mortar. These are the filler effect, the acceleration of ordinary Portland Cement Hydration and the pozzolanic reaction of MK with calcium hydroxide.