Development of geopolymer using industrial waste materials

Coal burned thermal power plants are producing large amounts of solid waste, fly ash. The disposal of this waste is a huge environmental problem at this moment. Generally, fly ash particles are very fine (<100 mu m) and mainly round shaped and glassy materials form an outer shell on it. According to several authors the attrition or grinding of this shell improves the activity of the fly ash. This paper deals with the laboratory investigation of ground fly ash based geopolymer. This material can be applied in many fields, mainly in the construction industry, e.g. non-structural elements, concrete, pavements and products, containment and immobilization of toxic, hazardous and radioactive wastes, advanced structural tooling and refractory ceramics, and fire resistant composites used in buildings, etc... In this study, the main process engineering properties of the raw materials, such as particle size distribution, moisture content, density and specific surface area are shown. Beside fly ash, red mud in different rate was used to prepare geopolymer. Systematic experimental series were carried out in order to optimize the preparation process. The particle size distribution of fly ash was measured by laser diffraction, the structure of fly ash and geopolymer was determined by Fourier Transformed Infrared Spectroscopy (FT-IR). The strength of the formed geopolymers was characterized by the uniaxial compressive strength. Additionally, leaching tests were carried out to monitor the stability of the main element of the fly ash. The product properties were studied as function of fly ash fineness. As a result of the investigation it was found that the geopolymer strength increased as function of fly ash fineness. Furthermore, it was established that the red mud had a positive effect on geopolymer strength. Therefore, the synergetic application of the above wastes is of good potential to create an industrial final product. Of course, several further experimental work is necessary to study the system from environmental point of view.