INFLUENCE of CIRCULATING FLUIDIZED BED COMBUSTION FLY ASHES on GROUND VITRIFIED BLAST FURNACE SLAG HYDRATION
The influence of Circulating Fluidized Bed Combustion (CFBC) fly ashes on Ground Vitrified Blast Furnace (GVBF) slag hydration has been studied on plain paste concerning strength and mineralogy. The paste was made by the mixture of 75% GVBF slag and 25% CFBC fly ash by weight. Three different CFBC fly ashes were used to activate the hydration of the slag. The result of this study shows that the hydration of GVBF slag can be activated and strengthened by the presence of CFBC fly ash. It is strongly influenced by the chemical composition of CFBC fly ash, particularly CaO and CaSO4. The paste containing more CaO and CaSO4 produced more flexural and compressive strength than the others. The development of this strength is relied by the massive formation of C-S-H gel combined with certain quantity of ettringite. These hydration products have been identified by X-ray diffraction and differential thermal analysis. In fact, this investigation reveals another possible way of the valorization of CFBC fly ashes in the field of civil engineering, especially as a constituent of a hydraulic binder in order to save energy and reduce costs.