Synthesis of solid activator for geopolymer product from fly ash and sodium hydroxide

Abstract

Fly ash is the residue from burning coal in industrial furnaces which is hazardous and toxic waste. Fly ash accumulates will be a problem for living things and the environment. One of the efforts to utilize fly ash as a geopolymer product. Geopolymer products need an activator, that is reactive when it reacts with water. In this study, a solid activator made from fly ash containing silica and sodium hydroxide. Making this solid activator by calcination. Fly ash is added with sodium hydroxide which is then calcined at 400 °C, 500 °C, and 650 °C for 2 hours. Then the solid activator is crushed and sieved. The analysis carried out is XRF to determine the chemical composition of fly ash and XRD to determine the crystallinity and mineral content of the fly ash and solid activator in several temperature variations. The results showed that fly ash from Muara Enim, South Sumatra was class F fly ash which mostly contains CaO (8.562%), SiO2 (45.324%), Al2O3 (23.967%), and Fe2O3 (12.998%). Solid activator is good for solid activator of geopolymer products, namely at a calcination temperature of 500 °C because of the higher conversion of active minerals (sodium silicate) in solid activator that is 39.5%.