• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.349-352
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• 2005

In this work, effects of limestone powder on hydration of $C_3A-CaSO_4\cdot2H_2O$ system was discussed based on the XRD Quantitative analysis, and the possibility of Delayed Ettringite Formation was also discussed. The early hydration of $C_{3}A$ was delayed by addition of $CaCO_{3}$ powder. The delay effect was enhanced by increasing of $CaCO_{3}$ content and finer powder of $CaCO_{3}$ addition. After consumption of $CaSO_4\cdot2H_2O$, the reaction of $CaCO_{3}$ is started. Delayed Ettringite Formation would take place because monosulfoaluminate is not stable in presence of $CaCO_{3}$. In order to prevent the delayed ettringite formation in $C_3A-CaSO_4\cdot2H_2O-CaCo_3$ system, the reduction of monosulfoaluminate formation is important. Therefore, by increasing the amount of $CaCO_{3}$ addition and finer $CaCO_{3}$ powder addition, the delayed ettringite formation can be prevented.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.584-588
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• 2011

In this work, effects of limestone powder on hydration of $C_3A-CaSO_4{\cdot}2H_2O$ system was discussed based on the XRD Quantitative analysis, and the possibility of Delayed Ettringite Formation was also discussed. The early hydration of $C_3A$ was delayed by addition of $CaCO_3$ powder. The delay effect was enhanced by increasing of $CaCO_3$ content and finer powder of $CaCO_3$ addition. After consumption of $CaSO_4{\cdot}2H_2O$, the reaction of $CaCO_3$ is started. Delayed Ettringite Formation would take place because monosulfoaluminate is not stable in presence of $CaCO_3$. In order to prevent the delayed ettringite formation in $C_3A-CaSO_4{\cdot}2H_2O-CaCO_3$ system, the reduction of monosulfoaluminate formation is important. Therefore, by increasing the amount of $CaCO_3$ addition and finer $CaCO_3$ powder addition, the delayed ettringite formation can be prevented.

• Journal of the Korean Ceramic Society
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• v.21 no.4
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• pp.355-360
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• 1984

The effect of 2% of $P_2O_5$ substituted in gypsum(5 mol% as $HPO_3$) on the early hydration characteristics of $C_3A$ were investigated and then gypsum only and gypsum mixed with $Ca(H_2PO_4)_2$.$H_2O$(2% as $P_2O_5$) were studied separately for comparison. The early hydration reaction of $C_3A$ with each gypsum were examined by measuring the rate of heat libera-tion of hydration with calorimeter and by analysing the hydration products with X-ray diffractometer and differential thermal analyser. It was shown that phosphogypsum substituted with $P_2O_6$ in the crystal lattice accelerated exceedingly the formation of the ettrignite and following hydrated products. However the other gypsum especially gypsum without any phosphate delayed the formation of various hydration products, It was consequently suggested that when phosphogypsum are used as the retarder of cement setting its reta-rding effect for setting of cement is not ascribed to the retardation of ettringite formation.

• Journal of the Korean Ceramic Society
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• v.40 no.1
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• pp.24-30
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• 2003

A formation and conversion of AFm phases decisively play role in the hydration, hardening and corrosion processes of various cement. In this study, the conversion of Alumino-Ferrite Monohydrates(AFm) phases under the addition of $CaCO_3,;CaCl_2;and;CaSO_4{cdot}2H_2O$was investigated by the XRD quantitative analysis. The thypical AFm phases are $M_S(monosulfoaluminate),;M_C(monocarboaluminate);and;M_{Cl}(monochloroaluminate and also Called Friedel's salts)$in this cementitious system, The conversion reaction were not occurred in $M_C-CaCO_3,;M_{Cl}-CaCO_3$ and $M_{Cl}-CaCl_2$system. However, in $M_S-CaCO_3$ system, ettringite and $monocarboaluminate(M_C)$ were formed. In $M_S-CaCl_2;system;M_S$ was transformed to Friedel's $salts(M_{Cl})$ and ettringite was formed. In the case of $CaSO_4{cdot}2H_2O$ addition, all AFm $phases(M_S,;M_C;and;M_{Cl})$ were transformed to ettringite. The order of stabilization of AFm phases under $CaCO_3,;CaCl_2;and;CaSO_4{cdot}2H_2O$ was as follows : $M_S< M_C