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Moises Frias - One of the best experts on this subject based on the ideXlab platform.
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Pozzolanic Reaction of a Biomass Waste as Mineral Addition to Cement Based Materials: Studies by Nuclear Magnetic Resonance (NMR)
International Journal of Concrete Structures and Materials, 2019Co-Authors: Sagrario Martínez-ramírez, Moises Frias, Erika Yukari Nakanishi, Holmer SavastanoAbstract:Non-fossil alternative fuels from biomass (agro-industrial, forestry and fodder plants) focus on getting cleaner, cheaper and more environmentally friendly energy sources directly related to the sustainable development of future societies. The resulting ash produced from the biomass calcination is a viable alternative for use as supplementary cementing materials in the construction industry. This study explores the scientific knowledge of calcium-silicate hydrate (C-S-H) gel formation during Pozzolanic Reaction between the biomass ash and calcium hydroxide through nuclear magnetic resonance technique with two different types of elephant grass ash that have different microstructure. The ash with the highest initial percentage of Q4 and Q3 units was found to react most actively and give rise to gels with the greatest inter-tetrahedral connectivity. In contrast, ash with higher content of total SiO2, exhibited lower reactivity and the C-S-H gel formed is characterised by low inter-tetrahedral connectivity from the earliest ages. Evaluation of C-S-H gel by nuclear magnetic resonance (NMR), as main hydrated phase for the engineering properties, revealed the potential of this tool to determine the effectiveness of this type of grass as raw material in cementing matrices through the evolution of the microstructure of the gel C-S-H formed.
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Chemical and mineral transformations that occur in mine waste and washery rejects during pre-utilization calcination
International Journal of Coal Geology, 2014Co-Authors: R. Vigil De La Villa, Moises Frias, Sagrario Martínez-ramírez, Rosario García-giménez, Lucía Fernández-carrascoAbstract:Abstract The mineralogical content of coal mine waste consists primarily of inorganic compounds which can be converted into a metakaolin-based product under controlled activation conditions that is also a highly Pozzolanic material. Activation temperatures ranging from 500 to 900 °C over 2 h retention time affect the mineralogy of coal mine waste, as well as the formation and evolution of the hydrated phases that form during the Pozzolanic Reaction. The hydrated phases formed during the Pozzolanic Reaction in the activated coal mine waste (ACMW)/Ca(OH) 2 system were C–S–H gels, stratlingite, tetracalcium aluminate hydrate, LDH compounds (phyllosilicate/carbonate) and monosulfoaluminate. Low temperatures (600 °C) favored the formation of LDH compounds and stratlingite; whereas monosulfoaluminate formed during the hydrated phase at higher temperatures (900 °C) during the first day of the Pozzolanic Reaction, and tetracalcium aluminate hydrate appeared as the dominant crystalline phase at 7 and 28 days.
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Evolution of Mineralogical Phases by 27Al and 29Si NMR in MK‐Ca(OH)2 System Cured at 60°C
Journal of the American Ceramic Society, 2013Co-Authors: Moises Frias, Sagrario Martínez-ramírez, T. Blasco, María Frías RodríguezAbstract:The evolution of the metastable phases in metakaolin/Ca(OH)2 systems cured at high temperatures, remains mostly unknown, newer techniques may now help to establish both the kinetic mechanism of the Pozzolanic Reaction and the thermodynamic stability of the main hydrated hexagonal phases: Stratlingite (C2ASH8) and tetra calcium aluminate hydrate (C4AH13). For this reason this work examines the kinetics of the Pozzolanic Reaction in the MK/Ca(OH)2 system over 123 d at 60°C using nuclear magnetic resonance spectroscopy (27Al and 29Si NMR). The results obtained by 27Al and 29Si NMR show that during the first 30 h, the metastable phases C2ASH8 and C4AH13, coexist with the cubic phase (C3ASH6) obtained directly from the Pozzolanic Reaction. The gel C–S–H is clearly identified after 21 h of Reaction, whereas at shorter times the C–S–H bands overlap those with the unreacted metakaolin ones. After 123 d of Pozzolanic Reaction, the first signs of the cubic phase are detected, a consequence of the conversion Reaction of the metastable phases, and a phenomenon not previously identified.
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Evolution of mineralogical phases produced during the Pozzolanic Reaction of different metakaolinite by-products: Influence of the activation process
Applied Clay Science, 2012Co-Authors: Moises Frias, Sara Goñi, R. Vigil, R. García, Olga Rodríguez, Iñigo VegasAbstract:Abstract In the past, different investigations have focused on waste containing kaolinite as an alternative source for recycled metakaolinite. However, it is well known that the activation conditions play an important role in the characteristics of the final product. This research presents an exhaustive study about the evolution of the mineralogical phases during the Pozzolanic Reaction of two metakaolinite by-products obtained from different activation processes: activation of paper sludge at lab scale (700 °C and 2 h) and at industrial scale (720–740 °C and 20–30 min) with a fluidized bed combustion system. It is shown that both metakaolinite by-products exhibit a different Pozzolanic behavior, suggesting a direct influence on the subsequent performance of new blended cement matrices. The metakaolinite by-product obtained at lab-scale (MWL), generates an additional phase (carbonate/metakaolinite type structures) as predominant crystalline phase in the pozzolan/Ca(OH) 2 system up to 28 days of Reaction. Stratlingite (C 2 ASH 8 ) also appeared as minor stable phase after 7 days of Reaction. On the other hand, the metakaolinite by-product from industrial process (MWI) favors the formation of C 4 A C ¯ H 12 phase, whereas stratlingite was not identified.
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Mineralogical and chemical evolution of hydrated phases in the Pozzolanic Reaction of calcined paper sludge
Cement and Concrete Composites, 2010Co-Authors: Raúl Fernández, Belén Nebreda, Raquel Vigil De La Villa, Rosario García, Moises FriasAbstract:Abstract Calcined residual paper sludge can be reused and valorized in a safe an environmental way by the construction industry. The highly reactive metakaolin produced by calcination of the paper sludge exhibits good Pozzolanic properties and permits its incorporation in cement systems. The Pozzolanic Reaction of metakaolin in Ca(OH) 2 -saturated solution at 40 °C is reported in this study as a function of time, up to 1 year. The stability of hydrates phases has been evaluated according to the evolving aqueous conditions. Analytical determinations of the solid phase show early formation of C–S–H phases and a later precipitation of laminar minerals, hydrotalcite and stratlingite, at the expense of the C–S–H phases. The thermodynamic calculations confirm the experimental observations.
Jan Elsen - One of the best experts on this subject based on the ideXlab platform.
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The Pozzolanic Reaction between clinoptilolite and portlandite: a time and spatially resolved IR study
European Journal of Mineralogy, 2010Co-Authors: Ruben Snellings, Gilles Mertens, Biliana Gasharova, Krassimir Garbev, Jan ElsenAbstract:The Pozzolanic Reaction of a natural zeolite-rich tuff and portlandite was investigated by means of IR spectroscopy. The zeolite tuff consisted mainly of Ca-rich clinoptilolite. A detailed analysis of the changes in the bonding environment during Reaction presented by the IR spectra showed that the vibrations assigned to the reactant phases were progressively consumed and implied that Si-rich environments were preferentially depleted. The contemporaneous appearance and rise of vibration bands characteristic for calcium-silicate-hydrates and calcium-aluminate-hydrates demonstrated the formation of Reaction products. Changes in bonding environment were spatially visualized by means of synchrotron-IR microspectroscopy. Promising results showed the distribution of reactants and Reaction products and allowed to analyze spatial trends in IR-vibration frequencies. A shift in calcium-silicate-hydrate mean peak position from 972 to 968 cm −1 indicated a decrease in silicate chain length with increasing distance from the clinoptilolite-matrix interface.
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early age hydration and Pozzolanic Reaction in natural zeolite blended cements Reaction kinetics and products by in situ synchrotron x ray powder diffraction
Cement and Concrete Research, 2010Co-Authors: Ruben Snellings, Gilles Mertens, Ozlem Cizer, Jan ElsenAbstract:The in situ early-age hydration and Pozzolanic Reaction in cements blended with natural zeolites were investigated by time-resolved synchrotron X-ray powder diffraction with Rietveld quantitative phase analysis. Chabazite and Na-, K-, and Ca-exchanged clinoptilolite materials were mixed with Portland cement in a 3:7 weight ratio and hydrated in situ at 40 {sup o}C. The evolution of phase contents showed that the addition of natural zeolites accelerates the onset of C{sub 3}S hydration and precipitation of CH and AFt. Kinetic analysis of the consumption of C{sub 3}S indicates that the enveloping C-S-H layer is thinner and/or less dense in the presence of alkali-exchanged clinoptilolite pozzolans. The zeolite Pozzolanic activity is interpreted to depend on the zeolite exchangeable cation content and on the crystallinity. The addition of natural zeolites alters the structural evolution of the C-S-H product. Longer silicate chains and a lower C/S ratio are deduced from the evolution of the C-S-H b-cell parameter.
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the zeolite lime Pozzolanic Reaction Reaction kinetics and products by in situ synchrotron x ray powder diffraction
Microporous and Mesoporous Materials, 2009Co-Authors: Ruben Snellings, Gilles Mertens, Sam Hertsens, Jan ElsenAbstract:Abstract The early Pozzolanic Reaction in pastes of lime and natural zeolites was studied with time-resolved in situ synchrotron X-ray powder diffraction. For chabazite and Na-, K-, and Ca-exchanged clinoptilolite tuffs, which were mixed with lime and water, the evolution of the quantitative contents of crystalline phases was followed during the early Pozzolanic Reaction in the first hours and days. The dependence of the rate coefficient on temperature was examined by isothermal curing at 313, 323, and 333 K of lime–chabazite tuff pastes. Kinetic analysis indicates that the Reaction rapidly displays a deceleratory character. This is explained by the modified Jander equation as a result of the Reaction rate control by diffusion processes through a condensing Reaction product boundary layer. The exchangeable cation content of clinoptilolite influences the duration of the initial induction period, the diffusion characteristics of the boundary layer of Reaction products, and the structural evolution of the C–S–H Reaction product. Alkali-exchanged clinoptilolites show a higher Pozzolanic reactivity, a more permeable Reaction product layer, and longer silicate chains in the C–S–H phase compared to their Ca-exchanged counterpart. The temperature dependence of the Reaction rate coefficients in the lime–chabazite tuff pastes obeys the Arrhenius equation.
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The zeolite–lime Pozzolanic Reaction: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction
Microporous and Mesoporous Materials, 2009Co-Authors: Ruben Snellings, Gilles Mertens, Sam Hertsens, Jan ElsenAbstract:Abstract The early Pozzolanic Reaction in pastes of lime and natural zeolites was studied with time-resolved in situ synchrotron X-ray powder diffraction. For chabazite and Na-, K-, and Ca-exchanged clinoptilolite tuffs, which were mixed with lime and water, the evolution of the quantitative contents of crystalline phases was followed during the early Pozzolanic Reaction in the first hours and days. The dependence of the rate coefficient on temperature was examined by isothermal curing at 313, 323, and 333 K of lime–chabazite tuff pastes. Kinetic analysis indicates that the Reaction rapidly displays a deceleratory character. This is explained by the modified Jander equation as a result of the Reaction rate control by diffusion processes through a condensing Reaction product boundary layer. The exchangeable cation content of clinoptilolite influences the duration of the initial induction period, the diffusion characteristics of the boundary layer of Reaction products, and the structural evolution of the C–S–H Reaction product. Alkali-exchanged clinoptilolites show a higher Pozzolanic reactivity, a more permeable Reaction product layer, and longer silicate chains in the C–S–H phase compared to their Ca-exchanged counterpart. The temperature dependence of the Reaction rate coefficients in the lime–chabazite tuff pastes obeys the Arrhenius equation.
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The zeolite–lime Pozzolanic Reaction: Reaction kinetics and products by in situ synchrotron X-ray powder diffraction
Microporous and Mesoporous Materials, 2009Co-Authors: Ruben Snellings, Gilles Mertens, Sam Hertsens, Jan ElsenAbstract:The early Pozzolanic Reaction in pastes of lime and natural zeolites was studied with time-resolved in situ synchrotron X-ray powder diffraction. For chabazite and Na-, K-, and Ca-exchanged clinoptilolite tuffs, which were mixed with lime and water, the evolution of the quantitative contents of crystalline phases was followed during the early Pozzolanic Reaction in the first hours and days. The dependence of the rate coefficient on temperature was examined by isothermal curing at 313, 323, and 333 K of lime–chabazite tuff pastes. Kinetic analysis indicates that the Reaction rapidly displays a deceleratory character. This is explained by the modified Jander equation as a result of the Reaction rate control by diffusion processes through a condensing Reaction product boundary layer. The exchangeable cation content of clinoptilolite influences the duration of the initial induction period, the diffusion characteristics of the boundary layer of Reaction products, and the structural evolution of the C–S–H Reaction product. Alkali-exchanged clinoptilolites show a higher Pozzolanic reactivity, a more permeable Reaction product layer, and longer silicate chains in the C–S–H phase compared to their Ca-exchanged counterpart. The temperature dependence of the Reaction rate coefficients in the lime–chabazite tuff pastes obeys the Arrhenius equation.status: publishe
L. Dimova - One of the best experts on this subject based on the ideXlab platform.
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On the kinetics of Pozzolanic Reaction in metakaolin–lime–water system
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: J. Ninov, I. Doykov, L. Dimova, B. Petrov, L. BrakalovAbstract:The kinetics of Pozzolanic Reaction metakaolin–lime is studied in the present work. Metakaolin is prepared by calcination of enriched kaolin (deposit “Senovo”, Bulgaria) at temperature of 830 ± 10 °C in a labscale muffle oven. The Reaction is performed in intensively stirred water suspension at different temperatures in the range 20–100 °C. The kinetics is analyzed by comparing the experimental data with theoretical curves, derived according to appropriate kinetic and diffusion models taking into account the grain size distribution of metakaolin. The macroscopic mechanism and activation energy of the Reaction are determined. It is found, that the activation energy decreases gradually from 71 to 45 kJ/mol[Ca(OH)2] with the increase of the Reaction degree from 0.2 up to 0.6, respectively, which is a characteristic for transition regime Reactions.
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on the kinetics of Pozzolanic Reaction in metakaolin lime water system
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: J. Ninov, I. Doykov, L. Dimova, B. Petrov, L. BrakalovAbstract:The kinetics of Pozzolanic Reaction metakaolin–lime is studied in the present work. Metakaolin is prepared by calcination of enriched kaolin (deposit “Senovo”, Bulgaria) at temperature of 830 ± 10 °C in a labscale muffle oven. The Reaction is performed in intensively stirred water suspension at different temperatures in the range 20–100 °C. The kinetics is analyzed by comparing the experimental data with theoretical curves, derived according to appropriate kinetic and diffusion models taking into account the grain size distribution of metakaolin. The macroscopic mechanism and activation energy of the Reaction are determined. It is found, that the activation energy decreases gradually from 71 to 45 kJ/mol[Ca(OH)2] with the increase of the Reaction degree from 0.2 up to 0.6, respectively, which is a characteristic for transition regime Reactions.
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on the kinetics of Pozzolanic Reaction in the system kaolin lime water
Journal of Thermal Analysis and Calorimetry, 2010Co-Authors: J. Ninov, I. Donchev, L. DimovaAbstract:The kinetics of the Pozzolanic Reaction of enriched kaolin from the “Senovo” deposit (Bulgaria) with lime is the object of this article. The kaolin contains kaolinite as a major clay mineral as well as admixtures of quartz and illite. The experimental data of Pozzolanic activity at temperatures of 100 and 23 °C are obtained for different Reaction times. The Reaction degrees of kaolinite and lime at 100 °C are determined from the Pozzolanic activity data using a powder X-ray diffraction analysis. The kinetic analysis is performed by joint presentation of theoretical and experimental data in dimensionless coordinates having in mind the influence of particle size distribution on the Reaction rate. It is found by the kinetic analysis that the rate of entire Reaction is limited by the rate of chemical Reaction on the Reaction surface up to degree of Reaction near to 0.4. The rate of penetration of the chemical Reaction into the kaolinite particles for this area—from the beginning to degree of Reaction 0.4, is determined to be equal to 2.10−11 m/s.
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On the kinetics of Pozzolanic Reaction in the system kaolin–lime–water
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: J. Ninov, I. Donchev, L. DimovaAbstract:The kinetics of the Pozzolanic Reaction of enriched kaolin from the “Senovo” deposit (Bulgaria) with lime is the object of this article. The kaolin contains kaolinite as a major clay mineral as well as admixtures of quartz and illite. The experimental data of Pozzolanic activity at temperatures of 100 and 23 °C are obtained for different Reaction times. The Reaction degrees of kaolinite and lime at 100 °C are determined from the Pozzolanic activity data using a powder X-ray diffraction analysis. The kinetic analysis is performed by joint presentation of theoretical and experimental data in dimensionless coordinates having in mind the influence of particle size distribution on the Reaction rate. It is found by the kinetic analysis that the rate of entire Reaction is limited by the rate of chemical Reaction on the Reaction surface up to degree of Reaction near to 0.4. The rate of penetration of the chemical Reaction into the kaolinite particles for this area—from the beginning to degree of Reaction 0.4, is determined to be equal to 2.10−11 m/s.
J. Ninov - One of the best experts on this subject based on the ideXlab platform.
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On the kinetics of Pozzolanic Reaction in metakaolin–lime–water system
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: J. Ninov, I. Doykov, L. Dimova, B. Petrov, L. BrakalovAbstract:The kinetics of Pozzolanic Reaction metakaolin–lime is studied in the present work. Metakaolin is prepared by calcination of enriched kaolin (deposit “Senovo”, Bulgaria) at temperature of 830 ± 10 °C in a labscale muffle oven. The Reaction is performed in intensively stirred water suspension at different temperatures in the range 20–100 °C. The kinetics is analyzed by comparing the experimental data with theoretical curves, derived according to appropriate kinetic and diffusion models taking into account the grain size distribution of metakaolin. The macroscopic mechanism and activation energy of the Reaction are determined. It is found, that the activation energy decreases gradually from 71 to 45 kJ/mol[Ca(OH)2] with the increase of the Reaction degree from 0.2 up to 0.6, respectively, which is a characteristic for transition regime Reactions.
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on the kinetics of Pozzolanic Reaction in metakaolin lime water system
Journal of Thermal Analysis and Calorimetry, 2011Co-Authors: J. Ninov, I. Doykov, L. Dimova, B. Petrov, L. BrakalovAbstract:The kinetics of Pozzolanic Reaction metakaolin–lime is studied in the present work. Metakaolin is prepared by calcination of enriched kaolin (deposit “Senovo”, Bulgaria) at temperature of 830 ± 10 °C in a labscale muffle oven. The Reaction is performed in intensively stirred water suspension at different temperatures in the range 20–100 °C. The kinetics is analyzed by comparing the experimental data with theoretical curves, derived according to appropriate kinetic and diffusion models taking into account the grain size distribution of metakaolin. The macroscopic mechanism and activation energy of the Reaction are determined. It is found, that the activation energy decreases gradually from 71 to 45 kJ/mol[Ca(OH)2] with the increase of the Reaction degree from 0.2 up to 0.6, respectively, which is a characteristic for transition regime Reactions.
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on the kinetics of Pozzolanic Reaction in the system kaolin lime water
Journal of Thermal Analysis and Calorimetry, 2010Co-Authors: J. Ninov, I. Donchev, L. DimovaAbstract:The kinetics of the Pozzolanic Reaction of enriched kaolin from the “Senovo” deposit (Bulgaria) with lime is the object of this article. The kaolin contains kaolinite as a major clay mineral as well as admixtures of quartz and illite. The experimental data of Pozzolanic activity at temperatures of 100 and 23 °C are obtained for different Reaction times. The Reaction degrees of kaolinite and lime at 100 °C are determined from the Pozzolanic activity data using a powder X-ray diffraction analysis. The kinetic analysis is performed by joint presentation of theoretical and experimental data in dimensionless coordinates having in mind the influence of particle size distribution on the Reaction rate. It is found by the kinetic analysis that the rate of entire Reaction is limited by the rate of chemical Reaction on the Reaction surface up to degree of Reaction near to 0.4. The rate of penetration of the chemical Reaction into the kaolinite particles for this area—from the beginning to degree of Reaction 0.4, is determined to be equal to 2.10−11 m/s.
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On the kinetics of Pozzolanic Reaction in the system kaolin–lime–water
Journal of Thermal Analysis and Calorimetry, 2009Co-Authors: J. Ninov, I. Donchev, L. DimovaAbstract:The kinetics of the Pozzolanic Reaction of enriched kaolin from the “Senovo” deposit (Bulgaria) with lime is the object of this article. The kaolin contains kaolinite as a major clay mineral as well as admixtures of quartz and illite. The experimental data of Pozzolanic activity at temperatures of 100 and 23 °C are obtained for different Reaction times. The Reaction degrees of kaolinite and lime at 100 °C are determined from the Pozzolanic activity data using a powder X-ray diffraction analysis. The kinetic analysis is performed by joint presentation of theoretical and experimental data in dimensionless coordinates having in mind the influence of particle size distribution on the Reaction rate. It is found by the kinetic analysis that the rate of entire Reaction is limited by the rate of chemical Reaction on the Reaction surface up to degree of Reaction near to 0.4. The rate of penetration of the chemical Reaction into the kaolinite particles for this area—from the beginning to degree of Reaction 0.4, is determined to be equal to 2.10−11 m/s.
Martin Keppert - One of the best experts on this subject based on the ideXlab platform.
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kinetics of Pozzolanic Reaction and carbonation in ceramic lime system thermogravimetry and solid state nmr spectroscopy study
Journal of building engineering, 2020Co-Authors: Martin Keppert, Lenka Scheinherrová, Libor Kobera, Jiří Brus, Magdaléna Doleželová, Robert CernýAbstract:Abstract Waste red-clay ceramic powder (RCC) is a Pozzolanic material which is currently not commercially used, but high amount of “brick fraction” of construction and demolition waste may become a source for a cheap Pozzolanic additive for Portland cement and lime-based binders. A sort of specific of RCC, compared to other pozzolans, is the higher content of non-reactive minerals. Pozzolanic Reaction, taking place in lime-based system, is inevitably accompanied by carbonation of the lime; these two processes are concurrent with respect to the lime consumption. Products of hydration (C–S–H and calcium aluminate hydrate phases) and carbonation (CaCO3) are contributing to the strengthening of the system. The goal of this research has been to evaluate the rate and mechanism of hardening of the RCC – lime mixtures. The relative rate of Pozzolanic Reaction and carbonation was studied over one-year period in RCC – lime pastes by help of thermal analysis and 23Na, 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy (MAS NMR), accompanied by porosimetry and compressive strength determination. The kinetics of lime conversion to hydration products and CaCO3 was determined by the help of thermogravimetry and described by Jander's equation. The highest rate of Pozzolanic Reaction, as well as the highest strength, reached mixture of 70% of RCC and 30% of lime; such high effective pozzolana content is caused by the phase composition of ceramic powder – it contains lower amount of reactive species, compared to metakaolin or other pozzolans. The formation of AlVI hydration products (AFm and AFt phases) took place within initial 3 days in all mixtures, while the content of C–S–H hydrates grown over the whole year of the experiment.
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Kinetics of Pozzolanic Reaction and carbonation in ceramic – lime system: Thermogravimetry and solid-state NMR spectroscopy study
Journal of Building Engineering, 2020Co-Authors: Martin Keppert, Lenka Scheinherrová, Libor Kobera, Jiří Brus, Magdaléna Doleželová, Robert ČernýAbstract:Abstract Waste red-clay ceramic powder (RCC) is a Pozzolanic material which is currently not commercially used, but high amount of “brick fraction” of construction and demolition waste may become a source for a cheap Pozzolanic additive for Portland cement and lime-based binders. A sort of specific of RCC, compared to other pozzolans, is the higher content of non-reactive minerals. Pozzolanic Reaction, taking place in lime-based system, is inevitably accompanied by carbonation of the lime; these two processes are concurrent with respect to the lime consumption. Products of hydration (C–S–H and calcium aluminate hydrate phases) and carbonation (CaCO3) are contributing to the strengthening of the system. The goal of this research has been to evaluate the rate and mechanism of hardening of the RCC – lime mixtures. The relative rate of Pozzolanic Reaction and carbonation was studied over one-year period in RCC – lime pastes by help of thermal analysis and 23Na, 27Al and 29Si Magic Angle Spinning Nuclear Magnetic Resonance Spectroscopy (MAS NMR), accompanied by porosimetry and compressive strength determination. The kinetics of lime conversion to hydration products and CaCO3 was determined by the help of thermogravimetry and described by Jander's equation. The highest rate of Pozzolanic Reaction, as well as the highest strength, reached mixture of 70% of RCC and 30% of lime; such high effective pozzolana content is caused by the phase composition of ceramic powder – it contains lower amount of reactive species, compared to metakaolin or other pozzolans. The formation of AlVI hydration products (AFm and AFt phases) took place within initial 3 days in all mixtures, while the content of C–S–H hydrates grown over the whole year of the experiment.
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Monitoring of Kinetics of Pozzolanic Reaction
Key Engineering Materials, 2016Co-Authors: Monika Čáchová, Lenka Scheinherrová, Libor Kobera, Martina Urbanova, Jiří Brus, Martin KeppertAbstract:The Pozzolanic additions are widely used as concrete component for numerous technical, economic and environmental reasons. Obviously the hydration process in a pozzolana containing system differs from hydration of Ordinary Portland Cement (OPC) what is indicated macroscopically by slower increase of strength and lower hydration heat. This paper aims to study Pozzolanic Reaction from perspective of chemical kinetics. From this point of view Pozzolanic Reaction and carbonation are two parallel Reactions which are competing for portlandite (Ca (OH)2). The rate of each of these two Reactions is characterized by rate constant and order of Reaction. The system under study was 1:1 mixture lime – ceramic powder. The course of Reaction was primarily studied by thermogravimetry which results were further subjected to kinetic analysis. MAS NMR spectroscopy was used for study of structural changes taking place in material in the course of Pozzolanic Reaction.