CHARACTERISTICS OF FLY ASH ADJUSTED IN PARTICLE SIZE BY CLASSIFICATION

Abstract

Removing the coarse particle fraction using air classification is effective approach in order to stabilize the chemical and physical properties of fly ash for use as a concrete admixture. We investigated the influence of fineness of fly ash which are adjusted using air classification on the several properties. The results revealed that the density, the flow value ratio and 28 day activity index of the classified fly ash increases with the increase in the fineness. On the other hand, chemical composition was almost unchanged regardless of the fineness. The reaction rate of fly ash increased linearly with the increase in specific surface area of the classified fly ash from 2,900 to 7,530cm²/g. The amorphous content of classified fly ash measured by XRD internal standard method slightly increased, but this effect on the increasing of reaction ratio of classified fly ash would be limited. Therefore 28 day activity index of classified fly ash is affected exclusively on the reaction ratio that mostly depend on the specific surface area.