Study on the pozzolanic activity of ultrafine circulating fluidized-bed fly ash prepared by jet mill

Abstract

The pozzolanic activity of ultrafine circulating fluidized-bed (CFB) fly ash prepared by jet mill has been investigated in this research. The ultrafine powder properties and the hydration heat release process of the cement blended with ultrafine CFB fly ash have been obtained. Furthermore, the dissolution characteristics of SiO2 and Al2O3, the Ca2+ absorption capacity in saturated Ca(OH)2 solution, and the polymerization degree of Si-O and Al-O polyhedrons have been studied to further clarify the mechanism of ultrafine grinding on pozzolanic activity. Compared to raw CFB fly ash (RCFA), the particle morphology, the pore structure of ultrafine CFB fly ash (UCFA, D50 ≤ 5 μm), and the pozzolanic activity of UCFA are significantly improved. The hydration rate of cement blended with UCFA is accelerated, and the total heat release is close to that of pure cement within 72 h. Ultrafine grinding increases the SiO2 and Al2O3 dissolution rate of CFB fly ash and Ca2+ absorption capacity in saturated Ca(OH)2 solution, mainly due to the decrease of polymerization degree of Si-O and Al-O polyhedrons and particle size of CFB fly ash.