Application of silica fume based solid activators for the one-part geopolymerization of aluminosilicate raw materials

Abstract

Geopolymerization stands out as the most promising technology to incorporate the sustainability principles in the construction sector. The research community has focused on altering the established two-part method of geopolymers production, where a corrosive alkaline solution is used to activate an aluminosilicate raw material, by introducing solid activators in the procedure (one-part synthesis procedure). Till today, most of the tested solid activators are commercial products with high embodied energy (e.g. Na2SiO3). However, an advanced solid activator was generated by our research team, through a simple procedure, where silica fume, sodium hydroxide and water were mixed and treated either thermally at 150 °C or by using a microwave for only 2 min to produce a solid powder with high Na2SiO3 content.This paper tests the scope of application of this new silica fume based solid activator by using it for the alkali activation of various established aluminosilicate raw materials in the geopolymerization technology: fly ash, ceramic waste (brick) and metakaolin. Initially, the raw materials were characterized in terms of their chemical and mineralogical composition. Then, the produced geopolymers’ compressive strength was examined and compared with two-part geopolymers reference samples. Finally, XRD quantitative analysis was applied to quantify the geopolymers’ crystalline and amorphous content in an effort to examine the efficiency of the new silica fume based solid activator.Results showed that the use of the proposed low embodied energy activator leads to geopolymers with comparable mechanical performance to those prepared with commercial reagents for all the examined aluminosilicate precursors, pointing out their future successful inclusion in the geopolymers market.