For recycling purposes, integrated gasification combined cycle (IGCC) slag and Si sludge were used as the basis for preparing lightweight panels with high compressive strength. The properties of the specimens were examined with the variation in the alkaline activator, addition of frames, addition of aluminum dihydrogen phosphate, particle-size separation of the IGCC slag, and variation in the specimen size by preparing large specimens with different W/S ratios and cutting the specimens at different positions. An optimum specimen with a low density and high compressive strength (8.1 MPa and 0.74 g cm^-3, respectively) was acquired from larger specimens (300 × 300 × 100 m³) having various densities and compressive strengths by controlling the W/S ratio and particle size of the IGCC slag. Therefore, it is expected that specimens with both, a low density and high compressive strength, can be obtained by developing and controlling the process factors during the production of lightweight geopolymers.

Keywords: Integrated gasification combined cycle slag, Si sludge, Lightweight, Compressive strength