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Karen Scrivener - One of the best experts on this subject based on the ideXlab platform.
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Factors influencing the Hydration Kinetics of ye'elimite; effect of mayenite
Cement and Concrete Research, 2019Co-Authors: Frank Bullerjahn, Maciej Zajac, Mohsen Ben Haha, Karen ScrivenerAbstract:Abstract The aim of this study was to understand the origin of the variation in the hydraulic reactivity of ye'elimite systems. To this end, the Hydration of two clinkers, one composed mainly of synthetic stoichiometric ( C 4 A 3 S ¯ ) “Y” and the other of an iron-bearing solid solution ( C 4 A 2.8 F 0.2 S ¯ ) “Fe-Y” ye'elimite, were studied. The Hydration sequences and main products were similar in both systems, but the Kinetics of the Fe-Y clinker were faster. The analyses of the solution composition at early times revealed an increase of the calcium and aluminium ion concentration for Fe-Y compared to Y, whereas the sulphate ion concentration was almost identical. This resulted in an initially higher oversaturation with respect to ettringite and monosulfate for the Fe-Y clinker. Experimental results demonstrate the accelerated formation of ettringite, which explained the faster early Hydration Kinetics. The cause for this was the presence of small amounts of mayenite (C12A7) in the Fe-Y clinker. The impact of mayenite was verified by the addition of synthetic mayenite to the stoichiometric ye'elimite clinker. Consequently, there is no evidence that presence of iron in the ye'elimite structure nor changes in polymorphism influence the hydraulic reactivity of ye'elimite.
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The Effect of Magnesium and Zinc Ions on the Hydration Kinetics of C3S
Journal of the American Ceramic Society, 2014Co-Authors: Amélie Bazzoni, Qianqian Wang, Xiadong Shen, Marco Cantoni, Karen ScrivenerAbstract:Impure tricalcium silicate (C3S) in portland cement may contain various foreign ions. These ions can stabilize different polymorphs of C3S at room temperature and may affect its reactivity. In this paper, the effects of magnesium and zinc on the polymorph type, Hydration Kinetics, and the hydrate morphology of C3S were investigated. The pure C3S has the T1 structure while magnesium and zinc stabilize polymorphs M3 and T2/T3, respectively. The two elements have distinct effects on the Hydration Kinetics. Zinc increases the maximum heat released. Magnesium increases the Hydration peak width. The C-S-H morphology is modified, leading to longer needles in the presence of zinc and thicker needles in the presence of magnesium. Zinc is incorporated into C-S-H, while magnesium is only incorporated slightly, if at all, but rather seems to inhibit nucleation. Implementing experimentally measured parameters for C-S-H nucleation and growth in the ic Hydration model captured well the observed changes in Hydration Kinetics. This supports C-S-H nucleation and growth to be rate controlling in the Hydration of C3S.
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Modelling early age Hydration Kinetics of alite
Cement and Concrete Research, 2012Co-Authors: Aditya Kumar, Shashank Bishnoi, Karen ScrivenerAbstract:The modelling platform mu ic [1] has been used to investigate the mechanisms occurring during the Hydration of alite. It is shown that it is possible to obtain a good simulation of the Hydration Kinetics through the implementation of two mechanisms: a dissolution mechanism combined with nucleation and growth of products. The dissolution rate is varied according to the ratio beta, between the ion activity product and the equilibrium solubility product according the theory published by Juilland et al. [2]. The solution concentrations are computed directly from the amount of alite dissolved taking into account the amount of water present and the amount of products formed, with activities and complex ion formation calculated according to standard methods. Saturation index calculations are implemented to compute the time of precipitation of C-S-H and portlandite (CH) individually. For the main heat evolution peak, the rate controlling mechanism switches to a modified form of boundary nucleation and growth. C-S-H grows in a diffuse manner in which the density of packing of the C-S-H phase increases with Hydration [3]. The rate of heat evolution obtained from the simulations is compared with isothermal calorimetry data and good agreement is found. (C) 2012 Elsevier Ltd. All rights reserved.
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Alite-ye’elimite clinker: Hydration Kinetics, products and microstructure
Construction and Building Materials, 1Co-Authors: Ruben Snellings, Xiaodong Shen, Karen ScrivenerAbstract:Abstract This paper presents the Hydration Kinetics, products and microstructure of an alite-ye’elimite clinker containing 4 wt% of ye’elimite to boost the early strength development. Isothermal calorimetry, X-ray diffraction, backscattered scanning electron microscopy and mercury intrusion porosimetry were used to study the Hydration processes. The results showed that the ye’elimite phase hydrated very rapidly, before the main Hydration of alite, forming ettringite as main Hydration product. The ye’elimite Hydration products precipitated throughout the pore space and reduced the microporosity of the hardened paste at early age. The presence of ye’elimite strongly affected the early Hydration before 24 h of Hydration, but did not show a significant effect on the Hydration Kinetics or products at later ages.
Jorgen Skibsted - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic modeling of hydrated white portland cement metakaolin limestone blends utilizing Hydration Kinetics from 29si mas nmr spectroscopy
Cement and Concrete Research, 2016Co-Authors: Wolfgang Kunther, Zhuo Dai, Jorgen SkibstedAbstract:Abstract Hydration Kinetics for the principal phases of Portland cement blends have been incorporated in thermodynamic modeling (GEMS package), utilizing degrees of Hydration from 29 Si 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, 27 Al and 29 Si 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 stratlingite 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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Thermodynamic modeling of hydrated white Portland cement–metakaolin–limestone blends utilizing Hydration Kinetics from 29Si MAS NMR spectroscopy
Cement and Concrete Research, 2016Co-Authors: Wolfgang Kunther, Zhuo Dai, Jorgen SkibstedAbstract:Abstract Hydration Kinetics for the principal phases of Portland cement blends have been incorporated in thermodynamic modeling (GEMS package), utilizing degrees of Hydration from 29 Si 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, 27 Al and 29 Si 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 stratlingite 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.
Wolfgang Kunther - One of the best experts on this subject based on the ideXlab platform.
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thermodynamic modeling of hydrated white portland cement metakaolin limestone blends utilizing Hydration Kinetics from 29si mas nmr spectroscopy
Cement and Concrete Research, 2016Co-Authors: Wolfgang Kunther, Zhuo Dai, Jorgen SkibstedAbstract:Abstract Hydration Kinetics for the principal phases of Portland cement blends have been incorporated in thermodynamic modeling (GEMS package), utilizing degrees of Hydration from 29 Si 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, 27 Al and 29 Si 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 stratlingite 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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Thermodynamic modeling of hydrated white Portland cement–metakaolin–limestone blends utilizing Hydration Kinetics from 29Si MAS NMR spectroscopy
Cement and Concrete Research, 2016Co-Authors: Wolfgang Kunther, Zhuo Dai, Jorgen SkibstedAbstract:Abstract Hydration Kinetics for the principal phases of Portland cement blends have been incorporated in thermodynamic modeling (GEMS package), utilizing degrees of Hydration from 29 Si 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, 27 Al and 29 Si 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 stratlingite 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.
Osamu Umezawa - One of the best experts on this subject based on the ideXlab platform.
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Effect of Geometric Factors on Hydration Kinetics of Theophylline Anhydrate Tablets
Journal of pharmaceutical sciences, 1992Co-Authors: Makoto Otsuka, Nobuyoshi Kaneniwa, Kuniko Otsuka, Katsumi Kawakami, Osamu Umezawa, Yoshihisa MatsudaAbstract:The effect of tablet thickness on the Hydration Kinetics of types I and II theophylline anhydrate tablets at 95% relative humidity and 35 degrees C was studied with various kinetic equations. Samples of 1- and 2-cm-diameter tablets (1 g) were compressed at 1000 kg/cm2. Types I and II tablets expanded by 11-17% in volume during Hydration to the monohydrate. The thickness expansion of all tablets exceeded the diameter expansion. After the hygroscopicity test, the final expansion ratio of type I tablets was more than that of type II tablets. The Hydration Kinetics analysis suggested that the Hydration of theophylline anhydrate tablets proceeds as follows: Hydration of the 1-cm-diameter type I tablet followed the two-dimensional phase boundary equation, and that of the 1-cm-diameter type II tablet followed the three-dimensional phase boundary equation, but those of the 2-cm-diameter types I and II tablets followed the equation for two-dimensional growth of nuclei. The Hydration Kinetics of tablets does not depend on the nature of bulk powder but on geometrical factors (tablet thickness and porosity).
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Effects of tableting pressure on Hydration Kinetics of theophylline anhydrate tablets.
The Journal of pharmacy and pharmacology, 1991Co-Authors: Makoto Otsuka, Nobuyoshi Kaneniwa, Katsumi Kawakami, Osamu UmezawaAbstract:The effects of tableting pressure on Hydration Kinetics of types I and II theophylline anhydrate tablets at 95% relative humidity, 35 degrees C, have been studied by using various kinetic equations. Relations between tablet expansion and Hydration were studied. Samples of 2 cm diameter tablets (1 g) were compressed at 5, 10 and 20 MPa. The Hydration of types I and II tablets decreased with increased tableting pressure. The time required for 50% Hydration of 2 cm diameter tablets, compressed at various pressures suggests that the tablet Hydration rate was affected by the tableting pressure. Types I and II tablets expanded 11.37-16.75% in volume during Hydration to the monohydrate. The thickness expansion of the tablets exceeded the diameter expansion as the tablet structure was not uniform owing to the orientation of particles during the compression. The final expansion ratio of the tablets increased with increased tableting compression pressure. The Hancock Sharp constant (m) and fitting of the kinetic data to a suitable model suggested that the Hydration of theophylline anhydrate tablets followed the two-dimensional phase boundary equation (type I tablets) or the three-dimensional phase boundary equation (type II tablets).
Makoto Otsuka - One of the best experts on this subject based on the ideXlab platform.
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Effect of Geometric Factors on Hydration Kinetics of Theophylline Anhydrate Tablets
Journal of pharmaceutical sciences, 1992Co-Authors: Makoto Otsuka, Nobuyoshi Kaneniwa, Kuniko Otsuka, Katsumi Kawakami, Osamu Umezawa, Yoshihisa MatsudaAbstract:The effect of tablet thickness on the Hydration Kinetics of types I and II theophylline anhydrate tablets at 95% relative humidity and 35 degrees C was studied with various kinetic equations. Samples of 1- and 2-cm-diameter tablets (1 g) were compressed at 1000 kg/cm2. Types I and II tablets expanded by 11-17% in volume during Hydration to the monohydrate. The thickness expansion of all tablets exceeded the diameter expansion. After the hygroscopicity test, the final expansion ratio of type I tablets was more than that of type II tablets. The Hydration Kinetics analysis suggested that the Hydration of theophylline anhydrate tablets proceeds as follows: Hydration of the 1-cm-diameter type I tablet followed the two-dimensional phase boundary equation, and that of the 1-cm-diameter type II tablet followed the three-dimensional phase boundary equation, but those of the 2-cm-diameter types I and II tablets followed the equation for two-dimensional growth of nuclei. The Hydration Kinetics of tablets does not depend on the nature of bulk powder but on geometrical factors (tablet thickness and porosity).
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Effects of tableting pressure on Hydration Kinetics of theophylline anhydrate tablets.
The Journal of pharmacy and pharmacology, 1991Co-Authors: Makoto Otsuka, Nobuyoshi Kaneniwa, Katsumi Kawakami, Osamu UmezawaAbstract:The effects of tableting pressure on Hydration Kinetics of types I and II theophylline anhydrate tablets at 95% relative humidity, 35 degrees C, have been studied by using various kinetic equations. Relations between tablet expansion and Hydration were studied. Samples of 2 cm diameter tablets (1 g) were compressed at 5, 10 and 20 MPa. The Hydration of types I and II tablets decreased with increased tableting pressure. The time required for 50% Hydration of 2 cm diameter tablets, compressed at various pressures suggests that the tablet Hydration rate was affected by the tableting pressure. Types I and II tablets expanded 11.37-16.75% in volume during Hydration to the monohydrate. The thickness expansion of the tablets exceeded the diameter expansion as the tablet structure was not uniform owing to the orientation of particles during the compression. The final expansion ratio of the tablets increased with increased tableting compression pressure. The Hancock Sharp constant (m) and fitting of the kinetic data to a suitable model suggested that the Hydration of theophylline anhydrate tablets followed the two-dimensional phase boundary equation (type I tablets) or the three-dimensional phase boundary equation (type II tablets).
