Synergistic effects of steel slag and spent fluid catalytic cracking catalysts on the geopolymer preparation: compressive strength, microstructure and gel structure

In this study, spent fluid catalytic cracking catalysts (FC) and metakaolin (MK) were used as reactive precursor to mix with steel slag (SS) for geopolymer preparation, in order to compare and analyze the synergistic effects of FC and SS in the geopolymer preparation. The results showed that the addition of reactive precursor (FC or MK) increased the gel content in the geopolymers, and the gel structure gradually transform from Q2 chain-like to Q4 network. When the reactive precursors to SS ratio is 6:4, the geopolymers contained approximately 10% C-S-H gel and 90% N (C)-A-S-H gel, and the geopolymer has optimal compressive strength. Although FC has lower reactivity than MK, it can continuously dissolve and undergo geopolymerization reaction in the alkaline environment generated during SS hydration. The generated gel effectively fills harmful pores in the geopolymers, thereby enhancing compressive strength of geopolymer.