Roles of hybrid activators in improving the early-age properties of one-part geopolymer pastes

Abstract The simple operation of one-part geopolymer has shown promising practicability for future in-situ construction similar to ordinary Portland cement. Intending to meet the demand of various industrial applications such as 3D printing, this study aims to tailor the early-age properties of one-part fly ash/ground granulated blast-furnace slag (FA/GGBS) geopolymer through the utilization of hybrid activators, such as anhydrous sodium metasilicate (Na2SiO3), sodium carbonate (Na2CO3), and sodium aluminate (NaAlO2). The reaction kinetics and chemistries of such alkali activators are expounded to understand the working principles and their contribution to the performance improvement of one-part geopolymer. The experimental results indicated that Na2SiO3-activated one-part geopolymer released high reaction heat and achieved a faster setting. Such shortcomings could be improved by partial replacement of Na2SiO3 with Na2CO3 in a solid form. Besides, the incorporation of slight NaAlO2 decreased the self-flow of geopolymer paste, whereas the slump-flow properties remained unchanged.