engleski

New perspectives for coal - ash utilisation: synthesis of geopolymeric materials

The present paper described and interprets experimental data on the synthesis and properties of fly ash-derived geopolymers, as an alternative use for coal-fly ash. In this study, Class F fly ash, which is high in aluminosilicate oxide and low in calcium oxide, form the Croatian coal-fired thermal power plant (Plomin2, Plomin) was used. The FA was treated with sodium silicate solution (a technical grade water glass, SiO2/Na2O = 3.1), and then thermally cured at 85 oC for different periods of time. Furier transforms infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM/EDS) have been used to identify the new phases and to follow the progress of their formation. In addition, the effects of different curing conditions on the mechanical strength development are discussed. It is observed that the glassy component of FA used reacted with water glass and the main reaction products formed in the geopolymeric materials was amorphous alkali aluminosilicate gel that induce a shift in the T-O (T= Si or Al) asymmetric stretching band towards lower frequency (1029 cm-1) related to ones in the original FA. The mean value of mechanical strengths increases as reaction time increases. The lineal correlation equations among flexural and compressive strength exists for all ages studied.

class F fly ash ; alkaline activation ; geopolymers ; mortars ; mechanical strength ; XRD ; FTIR ; SEM/EDS

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