PhD: Transformation of fly ash into new materials according to the tetrad syntesis-structure-properties-application

Biljana Angjusheva
Department of Inorganic Engineering, Faculty of Technology and Metallurgy, Ss. Cyril and Methodius University, Skopje, Macedonia
April, 2012


Waste fly ash from REK Bitola, Macedonia was used as a raw material for fabrication dense and porous ceramics, composite ceramics and glass ceramics. The waste fly ash and clay were specified from the following aspects: chemical, structural, thermo chemical, thermo physical and geometrical. Mechanical activation of the raw materials was applied in order to increase the geometrical and the structural factor of the activity.

The consolidation of the ceramics was performed in the temperature interval from 950 ºC to 1100 ºC/1h with heating rate of 3 and 10 ºC/min. The optimization process was conducted based on the influence of the main process parameters and their interactions on the ceramic properties. Density, mechanical properties (E-modulus, bending strength and compressive strength) and the technical coefficient of the thermal expansion were determined on the produced compacts.

The porous stricture was created using three types of pore creators i.e. two types of wood cutting and C-powder. It was confirmed that density, bending strength and E-modulus of thermal treated porous structures shows irreversible dependence on the ratio of the pore creator and linear dependence on the porosity and water absorption.

The concept of multibarier structure was employed to obtain the glass-ceramic composites based on fly ash and waste glass. As a source of liquid phase waste glass was used in quantity from 10 to 50 wt%. The mechanical properties, thermal stability and corrosive resistance of the glass-ceramic composites were specified.
Through a process of vitrification glass ceramics was also produced. The crystallization process for the glass ceramics was determined by defining the glass transition temperature (Tg), exothermic peak of crystallization (Tp), and endothermic peak of melting (Tm). The conversion of amorphous into crystal phases was confirmed by XRD analysis.
It was also confirmed that addition of 5 wt% TiO2 as nuclei affect the conversion of amorphous to crystal phase as well as mechanical properties of the glass-ceramics.