Pozzolanic reaction kinetics of coal ashes

Abstract

The pozzolanic reactivity was determined by the hydration kinetics of pozzolanic reaction based on the fact that the hydration products of active SiO₂ and Al₂O₃ with lime were soluble in dilute hydrochloric acid. The results show that the pozzolanic reaction of active SiO₂ and Al₂O₃ of coal ashes follows apparent first-order kinetics. The reaction rate constant of FBC ashes is greater than that of PC ashes, while the activation energy of the former is lower than that of the latter. It is confirmed that the pozzolanic activity of fluidized bed combustion(FBC) ashes is significantly higher than that of PC ashes, and the reaction barrier of the former is lower than that of the latter, because the microstructures of FBC ashes, such as mineralogical composition, morphology and polymerization degree of [SiO₄] and [AlO₆] are more favorable to the pozzolanic activity development than those of PC ashes.

Keywords

coal ashes / hydration / pozzolanic reactivity / kinetics

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