Effect of Fly Ash (FA) Characteristic on Geopolymer Product Quality

Fly Ash and Bottom Ash (FABA), a waste product in the form of ash from the burning coal at coal-fired power plants, is considered to have many advantages as the raw material for construction. One of the construction product examples is a geopolymer. This research aimed to determine the effect of the FABA characteristic on the compressive strength of geopolymer products. The source of fly ash (FA) used in this study is FA from Tanjung Jati B combustion power plant, Java, Indonesia which was characterized using petrographic analysis, XRD analysis, XRF analysis. Geopolymer was made with wet mixing methods and characterized using compressive strength tests and FTIR analysis. This study characterized the fly ash as having the dominant major oxides being Al2O3, SiO2, and Fe2O3. The inorganic components consist of glass, quartz, mullite, k-feldspar, fe-spinel, mg-spinel, hematite, magnetite, calcite, and kaolinite, while the inorganic components are dominated by glass materials, and the organic component consists of unburned coal (UC). Geopolymer, which is made, has a compressive strength average of 33 Mpa. A high value of SiO2/Al2O3, a high value of reactive SiO2, a low value of unburned carbon, and a low value of Fe2O3 affect the bond structure formed in the geopolymer and have a direct effect on increasing compressive strength. The results of this study could be used as a guide for determining the initial characteristics of FA in the manufacture of geopolymers with maximum quality.