Cement Clinker 燒成에서 CaF₂의 mineralizer 效果와 Cement 物性에 미치는 影響 Studies on the Mineralizing Effect of CaF₂ in the Burning of Cement Clinker and Its Influence on the Properties of Portland Cement
A new interpretation was given to the mineralizing mechanism of CaF₂ in the burning of cement clinker. Although the mineralizing effect of CaF₂ has been conventionally considered to be induced by flux action, the auther found that it had also the promoting activity for the formation of alite phase t...
A new interpretation was given to the mineralizing mechanism of CaF₂ in the burning of cement clinker. Although the mineralizing effect of CaF₂ has been conventionally considered to be induced by flux action, the auther found that it had also the promoting activity for the formation of alite phase through the solid phase reaction at a relatively lower temperature level. In the burning of cement raw mix with addition of CaF₂ the formation of alite phase was already confirmed at 1,100℃ by X-ray diffraction analysis. Therefore, the starting temperature of alite phase formation was about 200℃ lower than in the case of raw mix containing no CaF₂. With CaF₂ addition of more than 2%, the compound Ca₁₂Si₄O₁₉F₂ in the system CaOSiO₂-CaF₂ was clearly identified in the cooled clinker, its presence in the clinker induced the lacking of alite phase in quantity. Moreover, Ca₁₂Si₄O₁₉F₂ solid solution was formed by peritectic reaction with covering alite phase, these were considered to be causes of decline in the mechanical strength of cement burned with more than 2% CaF₂ addition. With CaF₂ addition, the formation of aluminate was bitterly prevented and finally disappeared. On the other hand, the amount of ferrite phase existing in the clinker increased as the fluorine content increased. The setting time of the clinker burned with CaF₂ addition is gradually delayed as the amount of CaF₂ increased. This delaying tendency appears remarkably in the final setting time. With CaF₂ addition of 1%, for instance, the initial setting starts after 4 hrs, 50 min, and the final setting comes to an end after 7 hrs, 25 min. It is, therefore, undesir able to increase CaF₂ more than 2% not only because of the mechanial strength but also of the setting time. In the burning of cement raw mix with the addition of CaF₂ the optimum dosage of CaF₂ was experimentally determined to be 0.5% level. In such a case it was possibly of no use to rise the burning temperature higher than 1,200℃. The cement clinker burned with the dosage of 0.5% CaF₂ at 1,200℃ beared resemblance to the ordinary clinker in its phisical properties except its slight tardiness of setting time.
A new interpretation was given to the mineralizing mechanism of CaF₂ in the burning of cement clinker. Although the mineralizing effect of CaF₂ has been conventionally considered to be induced by flux action, the auther found that it had also the promoting activity for the formation of alite phase through the solid phase reaction at a relatively lower temperature level. In the burning of cement raw mix with addition of CaF₂ the formation of alite phase was already confirmed at 1,100℃ by X-ray diffraction analysis. Therefore, the starting temperature of alite phase formation was about 200℃ lower than in the case of raw mix containing no CaF₂. With CaF₂ addition of more than 2%, the compound Ca₁₂Si₄O₁₉F₂ in the system CaOSiO₂-CaF₂ was clearly identified in the cooled clinker, its presence in the clinker induced the lacking of alite phase in quantity. Moreover, Ca₁₂Si₄O₁₉F₂ solid solution was formed by peritectic reaction with covering alite phase, these were considered to be causes of decline in the mechanical strength of cement burned with more than 2% CaF₂ addition. With CaF₂ addition, the formation of aluminate was bitterly prevented and finally disappeared. On the other hand, the amount of ferrite phase existing in the clinker increased as the fluorine content increased. The setting time of the clinker burned with CaF₂ addition is gradually delayed as the amount of CaF₂ increased. This delaying tendency appears remarkably in the final setting time. With CaF₂ addition of 1%, for instance, the initial setting starts after 4 hrs, 50 min, and the final setting comes to an end after 7 hrs, 25 min. It is, therefore, undesir able to increase CaF₂ more than 2% not only because of the mechanial strength but also of the setting time. In the burning of cement raw mix with the addition of CaF₂ the optimum dosage of CaF₂ was experimentally determined to be 0.5% level. In such a case it was possibly of no use to rise the burning temperature higher than 1,200℃. The cement clinker burned with the dosage of 0.5% CaF₂ at 1,200℃ beared resemblance to the ordinary clinker in its phisical properties except its slight tardiness of setting time.
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