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Daisuke Sawaki - One of the best experts on this subject based on the ideXlab platform.
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the role of steric repulsive force in the dispersion of Cement particles in Fresh Paste prepared with organic admixture
Cement and Concrete Research, 1997Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Daisuke SawakiAbstract:The existence of the steric repulsive force has never yet been determined, though the improved dispersibility of solid particles in concrete by adding the organic admixture is considered to be primarily caused by the dispersion of solid particles by the electrostatic repulsive force based on the formation of an electric double layer made of the admixture adsorbing to the surface of solid particles and the increase of the surface potential, and by the steric repulsive force based on the interaction between the adsorption layers of admixture. The authors proved for the first time the existence of the steric repulsive force acting on the surface of Cement particles adsorbing the organic admixture by measuring the interactive force between surface of Cement clinker adsorbing the admixture with an atomic force microscope, and measuring the zeta potential of Fresh Cement Paste under actual water-to-Cement ratio by electrokinetic sonic amplitude method. It is also clarified that the rate of contribution of electrostatic and steric repulsive force to the dispersion of Cement and hydrated Cement particles differs by the kind of organic admixture.
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influence of kind and added timing of organic admixture on the composition structure and property of Fresh Cement Paste
Cement and Concrete Research, 1995Co-Authors: Hiroshi Uchikawa, Daisuke Sawaki, Shunsuke HaneharaAbstract:Abstract It is well known that the fluidity and the setting time of Fresh concrete are affected by kind and added timing of organic admixture including fluidizing agent, air entraining agent and water reducing agent. The fluidity, setting time and time dependency of fluidity are measured using Fresh Cement Paste prepared with four kinds of organic admixtures, polycar☐ylic acid-based, aminosulfonic acid-based, β—naphthalenesulfonic acid-based and lignin sulfonic acid-based admixture, by two different methods of addition, that is, together with mixing water (simultaneous addition) and specified time after mixing with water (later addition). Hydration of Cement, adsorptive behavior of organic admixture to clinker minerals, formation of calcium complex with organic admixture and flocculation structure of Cement Paste are also estimated with the state-of-the-art method such as Auger electron spectroscopy, X-ray photoelectron spectroscopy and environmental scanning electron microscopy in order to clarify the influence of kind and added timing of admixture on the properties of Fresh Cement Paste and concrete and elucidate the mechanism of the improvement of fluidity of Cement Paste and concrete in later addition of admixture.
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effect of admixture on hydration of Cement adsorptive behavior of admixture and fluidity and setting of Fresh Cement Paste
Cement and Concrete Research, 1992Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Tokuhiko Shirasaka, Daisuke SawakiAbstract:The adsorptive behavior of admixtures and the hydration of Cement in the presence of admixtures were examined and the relationships of them with the physical properties of Fresh Cement Paste including fluidity, variation of fluidity with time and setting time were discussed with the quantitative determination of organic admixture adsorbed on the Cement, and with the observation and determination of the surface microstructure and composition of polished clinker dipped in aqueous solution containing a specified quantity of admixture by advanced method of surface analysis. In order to prepare the same fluidity of Fresh Cement Paste, mortar and concrete, the required amount of an easily adsorbed admixture is larger than that of a hard adsorbed one. An admixture having a functional group producing a complex salt with Ca2+ decreases the concentration of Ca2+ in liquid phase at early age and delays the saturation of Ca2+, which influences the morphology of hydrate produced, causes fluidity loss with time and delays the setting time of Cement. The microstructural and compositional estimations of the adsorption layer of admixture on the surface of clinker minerals by in-lens FESEM, ESCA-imaging, AES and AFM indicates that the admixture is partially adsorbed to the interstitial phase in a thick layer, forming characteristic three dimensional surface structure.
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Effect of admixture on hydration of Cement, adsorptive behavior of admixture and fluidity and setting of Fresh Cement Paste
Cement and Concrete Research, 1992Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Tokuhiko Shirasaka, Daisuke SawakiAbstract:The adsorptive behavior of admixtures and the hydration of Cement in the presence of admixtures were examined and the relationships of them with the physical properties of Fresh Cement Paste including fluidity, variation of fluidity with time and setting time were discussed with the quantitative determination of organic admixture adsorbed on the Cement, and with the observation and determination of the surface microstructure and composition of polished clinker dipped in aqueous solution containing a specified quantity of admixture by advanced method of surface analysis. In order to prepare the same fluidity of Fresh Cement Paste, mortar and concrete, the required amount of an easily adsorbed admixture is larger than that of a hard adsorbed one. An admixture having a functional group producing a complex salt with Ca2+ decreases the concentration of Ca2+ in liquid phase at early age and delays the saturation of Ca2+, which influences the morphology of hydrate produced, causes fluidity loss with time and delays the setting time of Cement. The microstructural and compositional estimations of the adsorption layer of admixture on the surface of clinker minerals by in-lens FESEM, ESCA-imaging, AES and AFM indicates that the admixture is partially adsorbed to the interstitial phase in a thick layer, forming characteristic three dimensional surface structure.
Hiroshi Uchikawa - One of the best experts on this subject based on the ideXlab platform.
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the role of steric repulsive force in the dispersion of Cement particles in Fresh Paste prepared with organic admixture
Cement and Concrete Research, 1997Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Daisuke SawakiAbstract:The existence of the steric repulsive force has never yet been determined, though the improved dispersibility of solid particles in concrete by adding the organic admixture is considered to be primarily caused by the dispersion of solid particles by the electrostatic repulsive force based on the formation of an electric double layer made of the admixture adsorbing to the surface of solid particles and the increase of the surface potential, and by the steric repulsive force based on the interaction between the adsorption layers of admixture. The authors proved for the first time the existence of the steric repulsive force acting on the surface of Cement particles adsorbing the organic admixture by measuring the interactive force between surface of Cement clinker adsorbing the admixture with an atomic force microscope, and measuring the zeta potential of Fresh Cement Paste under actual water-to-Cement ratio by electrokinetic sonic amplitude method. It is also clarified that the rate of contribution of electrostatic and steric repulsive force to the dispersion of Cement and hydrated Cement particles differs by the kind of organic admixture.
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influence of kind and added timing of organic admixture on the composition structure and property of Fresh Cement Paste
Cement and Concrete Research, 1995Co-Authors: Hiroshi Uchikawa, Daisuke Sawaki, Shunsuke HaneharaAbstract:Abstract It is well known that the fluidity and the setting time of Fresh concrete are affected by kind and added timing of organic admixture including fluidizing agent, air entraining agent and water reducing agent. The fluidity, setting time and time dependency of fluidity are measured using Fresh Cement Paste prepared with four kinds of organic admixtures, polycar☐ylic acid-based, aminosulfonic acid-based, β—naphthalenesulfonic acid-based and lignin sulfonic acid-based admixture, by two different methods of addition, that is, together with mixing water (simultaneous addition) and specified time after mixing with water (later addition). Hydration of Cement, adsorptive behavior of organic admixture to clinker minerals, formation of calcium complex with organic admixture and flocculation structure of Cement Paste are also estimated with the state-of-the-art method such as Auger electron spectroscopy, X-ray photoelectron spectroscopy and environmental scanning electron microscopy in order to clarify the influence of kind and added timing of admixture on the properties of Fresh Cement Paste and concrete and elucidate the mechanism of the improvement of fluidity of Cement Paste and concrete in later addition of admixture.
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effect of admixture on hydration of Cement adsorptive behavior of admixture and fluidity and setting of Fresh Cement Paste
Cement and Concrete Research, 1992Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Tokuhiko Shirasaka, Daisuke SawakiAbstract:The adsorptive behavior of admixtures and the hydration of Cement in the presence of admixtures were examined and the relationships of them with the physical properties of Fresh Cement Paste including fluidity, variation of fluidity with time and setting time were discussed with the quantitative determination of organic admixture adsorbed on the Cement, and with the observation and determination of the surface microstructure and composition of polished clinker dipped in aqueous solution containing a specified quantity of admixture by advanced method of surface analysis. In order to prepare the same fluidity of Fresh Cement Paste, mortar and concrete, the required amount of an easily adsorbed admixture is larger than that of a hard adsorbed one. An admixture having a functional group producing a complex salt with Ca2+ decreases the concentration of Ca2+ in liquid phase at early age and delays the saturation of Ca2+, which influences the morphology of hydrate produced, causes fluidity loss with time and delays the setting time of Cement. The microstructural and compositional estimations of the adsorption layer of admixture on the surface of clinker minerals by in-lens FESEM, ESCA-imaging, AES and AFM indicates that the admixture is partially adsorbed to the interstitial phase in a thick layer, forming characteristic three dimensional surface structure.
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Effect of admixture on hydration of Cement, adsorptive behavior of admixture and fluidity and setting of Fresh Cement Paste
Cement and Concrete Research, 1992Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Tokuhiko Shirasaka, Daisuke SawakiAbstract:The adsorptive behavior of admixtures and the hydration of Cement in the presence of admixtures were examined and the relationships of them with the physical properties of Fresh Cement Paste including fluidity, variation of fluidity with time and setting time were discussed with the quantitative determination of organic admixture adsorbed on the Cement, and with the observation and determination of the surface microstructure and composition of polished clinker dipped in aqueous solution containing a specified quantity of admixture by advanced method of surface analysis. In order to prepare the same fluidity of Fresh Cement Paste, mortar and concrete, the required amount of an easily adsorbed admixture is larger than that of a hard adsorbed one. An admixture having a functional group producing a complex salt with Ca2+ decreases the concentration of Ca2+ in liquid phase at early age and delays the saturation of Ca2+, which influences the morphology of hydrate produced, causes fluidity loss with time and delays the setting time of Cement. The microstructural and compositional estimations of the adsorption layer of admixture on the surface of clinker minerals by in-lens FESEM, ESCA-imaging, AES and AFM indicates that the admixture is partially adsorbed to the interstitial phase in a thick layer, forming characteristic three dimensional surface structure.
Shunsuke Hanehara - One of the best experts on this subject based on the ideXlab platform.
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the role of steric repulsive force in the dispersion of Cement particles in Fresh Paste prepared with organic admixture
Cement and Concrete Research, 1997Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Daisuke SawakiAbstract:The existence of the steric repulsive force has never yet been determined, though the improved dispersibility of solid particles in concrete by adding the organic admixture is considered to be primarily caused by the dispersion of solid particles by the electrostatic repulsive force based on the formation of an electric double layer made of the admixture adsorbing to the surface of solid particles and the increase of the surface potential, and by the steric repulsive force based on the interaction between the adsorption layers of admixture. The authors proved for the first time the existence of the steric repulsive force acting on the surface of Cement particles adsorbing the organic admixture by measuring the interactive force between surface of Cement clinker adsorbing the admixture with an atomic force microscope, and measuring the zeta potential of Fresh Cement Paste under actual water-to-Cement ratio by electrokinetic sonic amplitude method. It is also clarified that the rate of contribution of electrostatic and steric repulsive force to the dispersion of Cement and hydrated Cement particles differs by the kind of organic admixture.
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influence of kind and added timing of organic admixture on the composition structure and property of Fresh Cement Paste
Cement and Concrete Research, 1995Co-Authors: Hiroshi Uchikawa, Daisuke Sawaki, Shunsuke HaneharaAbstract:Abstract It is well known that the fluidity and the setting time of Fresh concrete are affected by kind and added timing of organic admixture including fluidizing agent, air entraining agent and water reducing agent. The fluidity, setting time and time dependency of fluidity are measured using Fresh Cement Paste prepared with four kinds of organic admixtures, polycar☐ylic acid-based, aminosulfonic acid-based, β—naphthalenesulfonic acid-based and lignin sulfonic acid-based admixture, by two different methods of addition, that is, together with mixing water (simultaneous addition) and specified time after mixing with water (later addition). Hydration of Cement, adsorptive behavior of organic admixture to clinker minerals, formation of calcium complex with organic admixture and flocculation structure of Cement Paste are also estimated with the state-of-the-art method such as Auger electron spectroscopy, X-ray photoelectron spectroscopy and environmental scanning electron microscopy in order to clarify the influence of kind and added timing of admixture on the properties of Fresh Cement Paste and concrete and elucidate the mechanism of the improvement of fluidity of Cement Paste and concrete in later addition of admixture.
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effect of admixture on hydration of Cement adsorptive behavior of admixture and fluidity and setting of Fresh Cement Paste
Cement and Concrete Research, 1992Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Tokuhiko Shirasaka, Daisuke SawakiAbstract:The adsorptive behavior of admixtures and the hydration of Cement in the presence of admixtures were examined and the relationships of them with the physical properties of Fresh Cement Paste including fluidity, variation of fluidity with time and setting time were discussed with the quantitative determination of organic admixture adsorbed on the Cement, and with the observation and determination of the surface microstructure and composition of polished clinker dipped in aqueous solution containing a specified quantity of admixture by advanced method of surface analysis. In order to prepare the same fluidity of Fresh Cement Paste, mortar and concrete, the required amount of an easily adsorbed admixture is larger than that of a hard adsorbed one. An admixture having a functional group producing a complex salt with Ca2+ decreases the concentration of Ca2+ in liquid phase at early age and delays the saturation of Ca2+, which influences the morphology of hydrate produced, causes fluidity loss with time and delays the setting time of Cement. The microstructural and compositional estimations of the adsorption layer of admixture on the surface of clinker minerals by in-lens FESEM, ESCA-imaging, AES and AFM indicates that the admixture is partially adsorbed to the interstitial phase in a thick layer, forming characteristic three dimensional surface structure.
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Effect of admixture on hydration of Cement, adsorptive behavior of admixture and fluidity and setting of Fresh Cement Paste
Cement and Concrete Research, 1992Co-Authors: Hiroshi Uchikawa, Shunsuke Hanehara, Tokuhiko Shirasaka, Daisuke SawakiAbstract:The adsorptive behavior of admixtures and the hydration of Cement in the presence of admixtures were examined and the relationships of them with the physical properties of Fresh Cement Paste including fluidity, variation of fluidity with time and setting time were discussed with the quantitative determination of organic admixture adsorbed on the Cement, and with the observation and determination of the surface microstructure and composition of polished clinker dipped in aqueous solution containing a specified quantity of admixture by advanced method of surface analysis. In order to prepare the same fluidity of Fresh Cement Paste, mortar and concrete, the required amount of an easily adsorbed admixture is larger than that of a hard adsorbed one. An admixture having a functional group producing a complex salt with Ca2+ decreases the concentration of Ca2+ in liquid phase at early age and delays the saturation of Ca2+, which influences the morphology of hydrate produced, causes fluidity loss with time and delays the setting time of Cement. The microstructural and compositional estimations of the adsorption layer of admixture on the surface of clinker minerals by in-lens FESEM, ESCA-imaging, AES and AFM indicates that the admixture is partially adsorbed to the interstitial phase in a thick layer, forming characteristic three dimensional surface structure.
Nicolas Roussel - One of the best experts on this subject based on the ideXlab platform.
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yield stress and bleeding of Fresh Cement Pastes
Cement and Concrete Research, 2012Co-Authors: Arnaud Perrot, Thibaut Lecompte, Coralie Brumaud, Nicolas RousselAbstract:Abstract We focus in this paper on a potential correlation between yield stress and bleeding. We suggest that the conditions under which a Fresh Cement Paste is able to display a yield stress result from the competition between Brownian motion and colloidal interactions whereas the conditions under which the suspension is stable result from the competition between colloidal interactions and gravity. These competitions highly depend on the solid volume fraction of the system and on the polymer surface coverage. The correlation between yield stress and bleeding is therefore very indirect and difficult to use in practice.
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lateral stress exerted by Fresh Cement Paste on formwork laboratory experiments
Cement and Concrete Research, 2008Co-Authors: J C Tchamba, Guillaume Ovarlez, Sofiane Amziane, Nicolas RousselAbstract:In the present paper, experimental results from laboratory testing on Cement Pastes are presented. The validity of both the predictions of the model proposed by Ovarlez and Roussel [Mat. and Struct. 39(2) (2006)] and the assumptions on which the model is based in the case of rough interfaces between the Cement Paste and the formwork surface are validated. The consistency of the underlying theory is tested in several different configurations (plate test with large and narrow gaps and a column test). Finally, the concept of a new test allowing the measurement of the structuration at rest of a Cementitious material is proposed. Such a simple test might be used to assess the input parameters needed to predict formwork pressure without the need for a rheometer.
F Puertas - One of the best experts on this subject based on the ideXlab platform.
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assessment of parameters governing the steel fiber alignment in Fresh Cement based composites
Construction and Building Materials, 2019Co-Authors: Victor Perez Villar, Nelson Flores Medina, M M Alonso, Sara Gismera Diez, F PuertasAbstract:Abstract The main aim of this paper is to measure the induced torque needed to rotate a steel fiber, hence an experimental and parametrical analysis of factors governing steel fiber alignment in Cement Pastes and mortar, rotating from static position and rotating in a dynamic fluid is here presented. To aim this objective, a set of rheological tests has been conducted to assess the torque necessary to rotate steel fibers immersed into different Fresh Cement Paste and mortar mixes with Bingham fluid behaviour. Fibers of different aspect ratios (length/width) and different geometry, straight and hooked-end, have been evaluated as they are the more commonly used. On the other hand, different parameters (type of mixture, size of aggregates, volume fraction of aggregates) affecting Cement mixtures are also analysed and their influence in fiber orientation discussed. Fiber alignment depends on external torques applied to fibers, immersed into a Cement-water-aggregate viscous system, that can be produced during or after casting. The flowability of the Fresh suspension with fibers produces a load/pressure that generates a torque that can align them. Fiber alignment is a main goal to pump the Fresh material. Hence, the factors that govern fiber alignment are studied which increase the post-cracking strength of Cement-based composites under load along its life service due to casting or pumping. To that end, a set of tests has been conducted to assess the torque necessary to rotate steel fibers immersed into different Fresh Cement Paste and mortar mixes with Bingham fluid behaviour. Fibers of different aspect ratios(length/width) and different geometry (straight and hooked-end) have been evaluated. On the other hand, different parameters (type of mixture, size of aggregates, volume fraction of aggregates) affecting Cement mixtures are also analysed and their influence on fiber orientation is discussed. The values obtained here are between 1 and 14 N · mm of dynamic yield torque and 0.1 and 0.5 N · mm min for viscoplastic torque per fiber, depending on fiber geometry, are helpful to improve the fiber alignment in Cement-based composites reinforced with fibers through a design and production based on these parameters.
