Herein, the variation in the mechanical properties of lightweight geopolymers, which contain integrated gasification combined cycle slag and Si sludge, were investigated by varying the curing conditions and introducing an additional drying process after immersion. The changes in the compressive strength and dentable characteristics were monitored for various samples corresponding to different curing conditions, immersion periods, and an optional post-immersion drying process. The microscopic morphology of the geopolymers was observed before and after immersion to investigate the enhancement in the mechanical properties of the geopolymers. The oven-cured specimens exhibited dentable characteristics, whereas the autoclaved specimens exhibited abrupt breakdown characteristics without any dentable characteristics. Further, the dentable characteristics observed in the specimens immersed for 3 days disappeared when the specimens were immersed for 7 days. The autoclaved specimens showed little difference in the compressive strength profile after 3 and 7 days of immersion; this stability in water indicates that the geopolymerization reaction was complete in the autoclaved specimens. In addition, after an additional oven drying process was used, a substantial increase in the compressive strength (from 4.1 to 7.1 MPa) was observed. It is speculated that the additional drying process promotes geopolymerization, which completes the reaction during the 1 day process

Keywords: Geopolymer, IGCC slag, Si sludge, Immersion, Curing, Aging