Performances and microstructure of one-part fly ash geopolymer activated by calcium carbide slag and sodium metasilicate powder

Abstract

As the raw material of geopolymer, F-class fly ash (FFA) often needs strong alkali such as NaOH to stimulate due to its low reactivity. In this study, FFA was refined and activated by a wet grinding process, and the activation effect of calcium carbide slag (19 %) and sodium silicate (1 %, 3 % and 5 %) was evaluated when used alone or in combination. The results show that the compound activator significantly improves the hydration products and mechanical properties of the wet-grinding FFA geopolymer. Compared with the single activation system, the 28-day hydration product content of the compound activation (co-activation) system increased by 67 %, and the 1-day compressive strength reached 24.8 MPa (at least an increase of 118 %). In addition, the co-activation system significantly improved the pore structure of the geopolymer and increased the chain length and Al/Si ratio of the C-S-H gel. The results of this study showed that co-activation and mechanical activation can significantly enhance the FFA geopolymer's mechanical characteristics and microstructure, greatly encourage the ingestion of industrial solid waste, lower the application costs of high pH activators, and efficiently provide a method for the utilization of FFA.