Geopolymers have attracted interest as an alternative to cement because they relase 80% lesser carbon dioxide than cement. Integrated gasification combined cycle (IGCC) slag was used as a raw material for the formation of the geopolymer. Many researchers have investigated the enhancement in the mechanical properties of geopolymers upon high-temperature heat treatment. However, there are few studies on the direct heat treatment of geopolymers. This study compared the effects of two different methods of heat treatment over a wide range of temperature. The highest compressive strength of 55.03 MPa was obtained at 200 o C after direct heat treatment. The X-ray diffraction patterns show that a new crystalline phase of calcium aluminum silicate was formed after heat-treatment at 1100 o C, which was confirmed by thermogravimetry-differential thermal analysis. In conclusion, the compressive strength of geopolymers can be enhanced and the density of geopolymers is also decreased by direct heat treatment at 200 o C. Thus, this approach can be used to make geopolymers for commercial products in the future.

Keywords: Geopolymer, IGCC slag, Direct heat treatment, Increasing-temperature heat treatment