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Qiang Wang - One of the best experts on this subject based on the ideXlab platform.
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influence of alkali activators on the Early Hydration of cement based binders under steam curing condition
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Dengquan Wang, Qiang Wang, Zhenggang FangAbstract:The effects of water glass, NaOH, Na2SO4, and Na2CO3 on the Early Hydration of plain cement and two composite binders incorporating 40 mass% ground granulated blast furnace slag (GGBS) and 40 mass% fly ash under the steam curing temperature of 60 °C were investigated. Meanwhile, a 20 °C curing condition was set as a reference. The results showed that water glass, NaOH, and Na2CO3 can improve the exothermic rates of the binders at the acceleration period and promote the reaction of GGBS and fly ash. However, the alkali activators inhibited the Hydration of Portland cement at the deceleration period, which was more significant at 60 °C. Thus, the alkali activators cannot efficiently increase the cumulative Hydration heat within 16 h under steam curing or even appear to decrease. Na2SO4 shows a better performance than the other three alkalis in the Early Hydration of the composite binders due to its promotion on the formation of AFt, but it cannot efficiently increase the cumulative Hydration heat too. The results also showed that all of the alkali activators significantly decreased the form-removal strength of cement–GGBS composite binder. For cement–fly ash composite binder, the form-removal strengths of the samples activated by a low concentration of water glass and high concentration of Na2SO4 were close to that reacted with water, while the form-removal strengths of the samples activated by other alkaline solutions were lower. Overall, the four alkali activators cannot improve the form-removal strength of steam-cured mortar containing a large volume of mineral admixtures.
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The difference among the effects of high-temperature curing on the Early Hydration properties of different cementitious systems
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Qiang Wang, Guohua JiangAbstract:The difference among the effects of high-temperature curing on the Early Hydration properties of the pure cement, the binder containing fly ash, the binder containing GGBS, and the binder containing steel slag was investigated by determining the compressive strength, non-evaporable water content, Hydration heat, and Ca(OH)2 content. Results show that the order of the influence degrees of high-temperature on the Early Hydration of different binders is the binder containing GGBS > the binder containing steel slag > the binder containing fly ash > the pure cement. In the case of short period of high-temperature curing (only 1 day), the strength growth rate of the concrete containing GGBS is the greatest. Though the influence of increasing high-temperature curing period on the Hydration degree of the binder containing fly ash is not the most significant, the strength growth rate of the concrete containing fly ash is the most significant due to the excessive consumption of Ca(OH)2 by reaction of fly ash. In the case of high-temperature curing, the Ca(OH)2 content of the paste containing steel slag is much higher than those of the paste containing GGBS and the paste containing fly ash, so though high-temperature curing promotes the Hydration of the binder containing steel slag significantly, its influence on the strength growth rate of the concrete containing steel slag is not so significant.
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a comparison of Early Hydration properties of cement steel slag binder and cement limestone powder binder
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Qiang WangAbstract:The Early Hydration properties of cement–steel slag composite binder and cement–limestone powder composite binder were compared in this study by determining the Hydration heat of binder within 3 days, the pore structure of paste and the compressive strength of mortar at the age of 3 days. Results show that at the curing temperature of 25 °C, the Early Hydration heat of the binder containing steel slag is smaller, and the Early pore structure of the paste containing steel slag is coarser, but the Early compressive strength of the mortar containing steel slag is higher compared with the mix containing limestone powder. Though the Early reaction degree of steel slag is low, its chemical contribution to the strength of mortar cannot be neglected. At the curing temperature of 50 °C, the Early Hydration heat of the binder containing steel slag is larger, and the Early pore structure of the paste containing steel slag is finer, and the Early compressive strength of the mortar containing steel slag is even higher compared with the mix containing limestone powder. Raising curing temperature can enhance the role played by steel slag more significantly than that played by limestone powder in the Hydration and hardening of the composite binder.
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A comparison of Early Hydration properties of cement–steel slag binder and cement–limestone powder binder
Journal of Thermal Analysis and Calorimetry, 2013Co-Authors: Peiyu Yan, Qiang WangAbstract:The Early Hydration properties of cement–steel slag composite binder and cement–limestone powder composite binder were compared in this study by determining the Hydration heat of binder within 3 days, the pore structure of paste and the compressive strength of mortar at the age of 3 days. Results show that at the curing temperature of 25 °C, the Early Hydration heat of the binder containing steel slag is smaller, and the Early pore structure of the paste containing steel slag is coarser, but the Early compressive strength of the mortar containing steel slag is higher compared with the mix containing limestone powder. Though the Early reaction degree of steel slag is low, its chemical contribution to the strength of mortar cannot be neglected. At the curing temperature of 50 °C, the Early Hydration heat of the binder containing steel slag is larger, and the Early pore structure of the paste containing steel slag is finer, and the Early compressive strength of the mortar containing steel slag is even higher compared with the mix containing limestone powder. Raising curing temperature can enhance the role played by steel slag more significantly than that played by limestone powder in the Hydration and hardening of the composite binder.
Theodor Staněk - One of the best experts on this subject based on the ideXlab platform.
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investigation on Early Hydration of ternary portland cement blast furnace slag metakaolin blends
Construction and Building Materials, 2014Co-Authors: Martin Bohac, Dalibor Vsianský, Radoslav Novotný, Jiří Másilko, Martin Palou, Theodor StaněkAbstract:Abstract The paper investigates the Hydration of ternary blends comprising Portland cement, blast-furnace slag and metakaolin. The isothermal calorimetry and “in situ” X-ray diffraction was used to evaluate the effect of metakaolin and blast-furnace slag on the Early Hydration of blends. XRD, DTA and SEM were used to analyze the hardened paste after 1 month of Hydration. Metakaolin influences significantly the kinetics, mechanism and products of Hydration at initial period of Hydration causing the rapid formation of ettringite. Hemicarbonate aluminate hydrate is formed as a product of ettringite conversion due to the presence of reactive calcite in Portland cement.
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Investigation on Early Hydration of ternary Portland cement-blast-furnace slag–metakaolin blends
Construction and Building Materials, 2014Co-Authors: Martin Bohac, Dalibor Vsianský, Radoslav Novotný, Jiří Másilko, Martin Palou, Theodor StaněkAbstract:Abstract The paper investigates the Hydration of ternary blends comprising Portland cement, blast-furnace slag and metakaolin. The isothermal calorimetry and “in situ” X-ray diffraction was used to evaluate the effect of metakaolin and blast-furnace slag on the Early Hydration of blends. XRD, DTA and SEM were used to analyze the hardened paste after 1 month of Hydration. Metakaolin influences significantly the kinetics, mechanism and products of Hydration at initial period of Hydration causing the rapid formation of ettringite. Hemicarbonate aluminate hydrate is formed as a product of ettringite conversion due to the presence of reactive calcite in Portland cement.
Peiming Wang - One of the best experts on this subject based on the ideXlab platform.
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Early Hydration of calcium sulfoaluminate cement in the presence of hydroxyethyl methyl cellulose
Journal of Thermal Analysis and Calorimetry, 2018Co-Authors: Guofang Zhang, Xiaopei Lu, Rui He, Peiming WangAbstract:The influence of hydroxyethyl methyl cellulose (HEMC) on the Early Hydration evolution of calcium sulfoaluminate (CSA) cement within 72 h was studied by using isothermal calorimetry, thermal analysis (TG–DTA), X-ray diffraction analysis, and environmental scanning electron microscopy. The results reveal that the HEMC definitely has different influences on the Hydration heat flow of CSA cement during different periods, postpones the occurrence time of two main heat flow peaks, and decreases the Early Hydration degree. HEMC assumes different influences on the formation and morphology evolution of hydrates with Hydration proceeding. HEMC manifests great retardation on the formation of AFt and AH_3 within 12 h of Hydration, whereas ensures higher AFt content and lower contents of AH_3 and AFm in cement paste after 24 h. Moreover, the influence of HEMC on the Early Hydration evolution of CSA cement enhances with its dosage increasing.
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Effects of super absorbent polymer on the Early Hydration of Portland cement highlighted by thermal analysis
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Guofang Zhang, Wang Yawen, He Rui, Peiming WangAbstract:The effects of super absorbent polymer (SAP) on the Early Hydration evolution of Portland cement within 72 h were investigated by isothermal calorimetry, thermal analysis and X-ray diffraction analysis. The results show that the SAP definitely affects the Early Hydration process of Portland cement, increases the Hydration heat evolution rate during the acceleration period and during the main exothermic peak, promotes the earlier appearance of the main exothermic peak, but does not affect the lengths of the initial reaction period and the induction period and the onset of the acceleration period. The SAP can accelerate cement Hydration to increase the Hydration degree within 72 h. But the dosage variation of SAP has minor influence on the Hydration heat evolution and Hydration degree. The SAP enhances the formation of Ca(OH)2 after 12 h to keep higher content than that in the reference paste. The SAP does not affect the maximum content of ettringite, but delays the conversion of ettringite to monosulphate to remain ettringite content higher at later Hydration time. Besides, no new phases are found to have formed in cement paste with SAP.
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Effect of HEMC on the Early Hydration of Portland cement highlighted by isothermal calorimetry
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Guofang Zhang, Zhao Jianbin, Peiming WangAbstract:The effects of hydroxyethyl methyl cellulose (HEMC) on the Early Hydration and main hydrates evolutions of Portland cement were quantitatively investigated by the isothermal calorimetry, setting times, X-ray diffraction analysis, and environmental scanning electron microscope analysis. The results show that HEMC definitely affects the Early Hydration process of cement paste and retards the beginning of the Hydration induction period and acceleration period, but increases the length of these two periods. HEMC decreases the Hydration heat evolution rate during the initial reaction period and the acceleration period, but increases the Hydration heat evolution rate during the deceleration period. HEMC decreases the Hydration heat amount and Hydration degree of cement paste at the Early Hydration time, especially in the first thirty-six hours. There are good positive correlations between the setting time, the length of induction period and the dosages of HEMC. HEMC also delays the formation of the hydrates and affects the morphologies of hydrates. Accordingly, HEMC remarkably retards the cement Hydration at the Early Hydration time, and with its dosage increasing, the retardation effect of HEMC enhances.
Martin Bohac - One of the best experts on this subject based on the ideXlab platform.
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Early Hydration of C2S doped with combination of S and Li
SN Applied Sciences, 2020Co-Authors: Martin Bohac, Theodor Staněk, Anežka Zezulová, Alexandra Rybová, F. Bellmann, H.-m. LudwigAbstract:Production of low-energy cements would result in energy saving and lower CO2 emissions related to reduced consumption of fuel and high-grade limestone as a raw material. Belite rich clinker, made more reactive by doping with combination of S and Li, could possibly be one of the low-energy alternatives for Portland cement clinker. Paper describes the preparation of doped belite and deals with its Early Hydration and reactivity. Belite rich clinkers were prepared in laboratory in high-temperature solid state synthesis. Pure substances were used for the preparation of raw meal and clinker. Early Hydration heat flow development of cement pastes was monitored by isothermal calorimetry, changes in phase composition by “in situ” X-ray diffraction and TGA/DTA and microstructure by SEM-SE. Heat flow exotherms were correlated with quantified phase composition at given time. Intensity and position of main exothermic peak related to Hydration of C3S is changing with increasing Li content. Doping of the C2S by the S or the combination of S and Li significantly increases the reactivity of the C2S-rich cement. The formation of C–S–H products is a continuous process that depends mainly on C3S during first 6 h and then is supported by slow reaction of β-C2S. The reactivity of C2S is affected by the timing of the Hydration of other clinker phases. Two generations of portlandite formation detectable as a double endotherm on TGA/DTA can be attributed to Hydration of C3S and β-C2S.
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Early Hydration of Activated Belite-Rich Cement
Advanced Materials Research, 2019Co-Authors: Martin Bohac, Theodor Staněk, Anežka Zezulová, Alexandra Rybová, Dana Kubátová, Radoslav NovotnýAbstract:Implementation of high belite cement in cement production would have strong environmental impact in reduction CO2 emissions and saving of pure limestone deposits. The goal of the study is to describe the role of alkali and C-S-H activators on Hydration of high belite cement. Analytical approach for Early Hydration is based on combination of isothermal calorimetry, X-ray powder diffraction in-situ, DTA-TG, FT-IR.
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Rheological and Calorimetric Characterization of the Role of CaCl2 on Portland Cement Early Hydration
Materials Science Forum, 2016Co-Authors: Martin Bohac, Radoslav NovotnýAbstract:Paper describes a new way how to characterize Early Hydration and setting of Portland cement pastes with various dosages of setting accelerator CaCl2. The aim was not to characterize the role of well-known setting accelerator CaCl2 but to correlate rheology and calorimetry in view of Early Hydration of Portland cement. Characterization was based on measurements on rotational rheometer, isothermal calorimeter and semiadiabatic calorimeter. The courses of calorimetric exotherms in time were correlated to the development of the phase angle obtained by rheological oscillation tests. Heat flow peaks can be successfully correlated to rheological processes described by change of storage and elastic moduli up to the time that corresponds to the start of the setting which was found to be the limit for rheological tests. The start of the setting on calorimetric curve belongs to the onset point of the main silicate peak during acceleration period of Hydration. The value of phase angle decreases as the setting cement paste changes from liquid to solid-like. Times of low values of phase angle ~ 2.5 (°) can be related to times of onset points of main peak for every dosage of setting accelerator.
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investigation on Early Hydration of ternary portland cement blast furnace slag metakaolin blends
Construction and Building Materials, 2014Co-Authors: Martin Bohac, Dalibor Vsianský, Radoslav Novotný, Jiří Másilko, Martin Palou, Theodor StaněkAbstract:Abstract The paper investigates the Hydration of ternary blends comprising Portland cement, blast-furnace slag and metakaolin. The isothermal calorimetry and “in situ” X-ray diffraction was used to evaluate the effect of metakaolin and blast-furnace slag on the Early Hydration of blends. XRD, DTA and SEM were used to analyze the hardened paste after 1 month of Hydration. Metakaolin influences significantly the kinetics, mechanism and products of Hydration at initial period of Hydration causing the rapid formation of ettringite. Hemicarbonate aluminate hydrate is formed as a product of ettringite conversion due to the presence of reactive calcite in Portland cement.
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Investigation on Early Hydration of ternary Portland cement-blast-furnace slag–metakaolin blends
Construction and Building Materials, 2014Co-Authors: Martin Bohac, Dalibor Vsianský, Radoslav Novotný, Jiří Másilko, Martin Palou, Theodor StaněkAbstract:Abstract The paper investigates the Hydration of ternary blends comprising Portland cement, blast-furnace slag and metakaolin. The isothermal calorimetry and “in situ” X-ray diffraction was used to evaluate the effect of metakaolin and blast-furnace slag on the Early Hydration of blends. XRD, DTA and SEM were used to analyze the hardened paste after 1 month of Hydration. Metakaolin influences significantly the kinetics, mechanism and products of Hydration at initial period of Hydration causing the rapid formation of ettringite. Hemicarbonate aluminate hydrate is formed as a product of ettringite conversion due to the presence of reactive calcite in Portland cement.
Guofang Zhang - One of the best experts on this subject based on the ideXlab platform.
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Early Hydration of calcium sulfoaluminate cement in the presence of hydroxyethyl methyl cellulose
Journal of Thermal Analysis and Calorimetry, 2018Co-Authors: Guofang Zhang, Xiaopei Lu, Rui He, Peiming WangAbstract:The influence of hydroxyethyl methyl cellulose (HEMC) on the Early Hydration evolution of calcium sulfoaluminate (CSA) cement within 72 h was studied by using isothermal calorimetry, thermal analysis (TG–DTA), X-ray diffraction analysis, and environmental scanning electron microscopy. The results reveal that the HEMC definitely has different influences on the Hydration heat flow of CSA cement during different periods, postpones the occurrence time of two main heat flow peaks, and decreases the Early Hydration degree. HEMC assumes different influences on the formation and morphology evolution of hydrates with Hydration proceeding. HEMC manifests great retardation on the formation of AFt and AH_3 within 12 h of Hydration, whereas ensures higher AFt content and lower contents of AH_3 and AFm in cement paste after 24 h. Moreover, the influence of HEMC on the Early Hydration evolution of CSA cement enhances with its dosage increasing.
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Effects of super absorbent polymer on the Early Hydration of Portland cement highlighted by thermal analysis
Journal of Thermal Analysis and Calorimetry, 2017Co-Authors: Guofang Zhang, Wang Yawen, He Rui, Peiming WangAbstract:The effects of super absorbent polymer (SAP) on the Early Hydration evolution of Portland cement within 72 h were investigated by isothermal calorimetry, thermal analysis and X-ray diffraction analysis. The results show that the SAP definitely affects the Early Hydration process of Portland cement, increases the Hydration heat evolution rate during the acceleration period and during the main exothermic peak, promotes the earlier appearance of the main exothermic peak, but does not affect the lengths of the initial reaction period and the induction period and the onset of the acceleration period. The SAP can accelerate cement Hydration to increase the Hydration degree within 72 h. But the dosage variation of SAP has minor influence on the Hydration heat evolution and Hydration degree. The SAP enhances the formation of Ca(OH)2 after 12 h to keep higher content than that in the reference paste. The SAP does not affect the maximum content of ettringite, but delays the conversion of ettringite to monosulphate to remain ettringite content higher at later Hydration time. Besides, no new phases are found to have formed in cement paste with SAP.
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Effect of HEMC on the Early Hydration of Portland cement highlighted by isothermal calorimetry
Journal of Thermal Analysis and Calorimetry, 2014Co-Authors: Guofang Zhang, Zhao Jianbin, Peiming WangAbstract:The effects of hydroxyethyl methyl cellulose (HEMC) on the Early Hydration and main hydrates evolutions of Portland cement were quantitatively investigated by the isothermal calorimetry, setting times, X-ray diffraction analysis, and environmental scanning electron microscope analysis. The results show that HEMC definitely affects the Early Hydration process of cement paste and retards the beginning of the Hydration induction period and acceleration period, but increases the length of these two periods. HEMC decreases the Hydration heat evolution rate during the initial reaction period and the acceleration period, but increases the Hydration heat evolution rate during the deceleration period. HEMC decreases the Hydration heat amount and Hydration degree of cement paste at the Early Hydration time, especially in the first thirty-six hours. There are good positive correlations between the setting time, the length of induction period and the dosages of HEMC. HEMC also delays the formation of the hydrates and affects the morphologies of hydrates. Accordingly, HEMC remarkably retards the cement Hydration at the Early Hydration time, and with its dosage increasing, the retardation effect of HEMC enhances.
