In this study, we used integrated gasification combined cycle (IGCC) fused slag, a by-product of IGCC, to analyze its applicability as a high-strength geopolymer in terms of particle size, alkaline activator concentration, and solid-liquid ratio. We also examined its stability. A planetary ball mill was employed to pulverize the slag for 4, 6, and 8 h so as to adjust the particle size to a desired value. The results showed that the compressive strength of the geopolymer made of the 6 h pulverized material and 12 M alkaline activator was the highest (29.8MPa). In the case of the 8h pulverized material, the compressive strength of the geopolymer got weaker. Therefore, it was found that an optimal particle size was necessary for strength development. When the IGCC fused slag was finely pulverized (average particle size = 128 μm, the strength increased with an increase in the molar concentration. At 18M, the maximum strength was 59.908 MPa. A heavy metal dissolution test was performed. The specimen's heavy metal dissolution was detected to be lower than the reference value. Hence, the specimen was found to be safe. Therefore, if IGCC fused slag with an optimum particle size is used the resulting geopolymer can be applied as a construction material.

Keywords: Integrated Gasification Combined Cycle (IGCC) slag, Particle size, Molar concentration (Mol), Compressive strength, Water/soild (W/S) ratio.