Effects of Calcium Contents in Class C Fly Ash Geopolymer

Geopolymers with calcium contents were prepared from class C fly ash, metakaolin, and Ca(OH)(2). Geopolymer products and ordinary cement hydration products were divided with gradient acid dissolution test. The effects of calcium in class C fly ash geopolymer were investigated through the calcium concentration of acid solution. In an appropriate alkali situation, most of the calcium will be dissolved from class C fly ash. Part of the calcium will react with silicate and aluminum to form geopolymeric gels as the presence of gismondine (zeolite). Part of calcium was hydrated to form calcium silicate hydrate(C-S-H), and the rest of calcium may be adsorbed within the geopolymeric binding structure to balance charge anion. The class C fly ash geopolymer is a composite system with the coexistence of geopolymeric and C-S-H gels.