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Kinetics of the Reaction of Calcium Hydroxide and Fly Ash.


pdf icon Kinetics of the Reaction of Calcium Hydroxide and Fly Ash. (3018 K)
Biernacki, J. J.; Williams, P. J.; Stutzman, P. E.

Title No. 98-M37;

ACI Materials Journal, Vol. 98, No. 4, 340-349, July/August 2001.

Keywords:

fly ash; kinetics; hydration kinetics; pozzolans; pozzolanic reaction; cements

Abstract:

The reaction kinetics of a Type-F fly ash with calcium hydroxide (CH) has been investigated at temperatures between 25 {degrees}C and 60 {degrees}C. Thermogravimetric analysis (TGA) was used to determine CH consumption and production of hydrates (non-evaporable water) as a function of hydration temperature and time for various CH/fly ash ratios. The results indicate that the reaction rate, reaction stoichiometry and activation energy are dependent on the CH/ash ratio. The reaction rate was also found to be a function of the extent of reaction of both CH and fly ash phases. Various kinetic models were considered including those proposed by Knudsen and Avrami. These, however, were found to have limited applicability. A model is suggested that provides a broader fit to the observed data.