HEAT EVOLUTION AND MECHANISM OF HYDRATION IN CaO-Al2O3-SO3 SYSTEM

The hydration behaviour of the CaO-Al2O3-SO3 system was investigated over the temperature range 25-80 C and at water/solid ratios 0.5, 0.7 and 1.0 using an isothermal conduction calorimeter. In the defined system, 4CaO-3Al2O3-SO3, known as Klein compound, was supposed to be the main mineral phase. A...

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Bibliographic Details
Published in:Ceramics (Praha) 2005-01, Vol.49 (2), p.104-108
Main Authors: Doval, M, Palou, M, Kovar, V
Format: Article
Language:English
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Summary:The hydration behaviour of the CaO-Al2O3-SO3 system was investigated over the temperature range 25-80 C and at water/solid ratios 0.5, 0.7 and 1.0 using an isothermal conduction calorimeter. In the defined system, 4CaO-3Al2O3-SO3, known as Klein compound, was supposed to be the main mineral phase. An increase in the temperature of hydration brought about initial acceleration of all samples treated under different water/solid ratios, as indicated by an increased hydration rate. There was clear evidence of increasing intensity of the main peaks with increasing water/solid ratio at hydration temperatures of 25 C and 40 C, whereas at higher temperatures (60 C and 80 C), the magnitude of hydration decreased with increasing water/solid ratio. Kinetics of hydration of Klein compound could be described by an Avrami model. The value of kinetic exponent n = 3 implied that the hydration was controlled by nucleation and three-dimensional crystal growth. Calculated values of activation energy for water/solid ratios 0.5, 0.7 and 1.0 were 21.0, 17.2 and 16.4 kJ/mol respectively. 21 refs.
ISSN:0862-5468