Synthesis And Characterization Of Fly-Ash-Based Na-Geopolymer

In present thesis, fly ash, NaOH and water-glass chose as the main raw materials were used to prepare geopolymers. A method of combining X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), thermogravimetry-differential scanning calorimetry (TG-DSC) and specific surface area and porosity analyzer technicaques had been established to characterize the structural composition of geopolymers. Geopolymers materials as cement and light weight thermal insulation materials were investageted. The fast-setting technology was developed. The resistance to high concentration sulfuric acid attack of geopolymer was studied and the machism of corrosion resistance was developed. The dry-pressed forming technology was utilized to prepared high strength geopolymers. The compressive strength of geopolymer cement by optimum process was 51.2MPa at 28d and 71.6MPa at 180d respectively. The strength and setting time can be controlled simultaneously by adjusting the volume of alkali and the amount and variety of calcium additives. After 100 freeze-thaw cycles,80%strength of the geopolymer cement was remained, and after 12 months of chemical corrosion 10-60%of the strength was remained. With the addition of surfactant, the size of pores in geopolymers foam was decreased from about 1-20mm to less 2mm. The optiumum compressive strength was 2.57MPa and density was 0.76g/cm3. Microwave radiation technology enabled geopolymers to reach demoulding strength (3.3-6.5MPa) at 9-15min, and the strength increased with ages prolonging as that of control sample. The corrosion mechanism of geopolymers in high concentration of sulfuric acid solution includes:the diffusion (counter-diffusion), ion-exchange reactions and reorganization. The highest strength of geopolymers by dry-pressed forming process was 180MPa, which was twice as high as that of geopolymers by casting forming process, while calcined at 1200℃more than 70%of the strength was remained.