Development of sustainable geopolymer materials made with ground geopolymer waste powder as renewable binder up to 100%

Reusing ground geopolymer waste powder (GWP) as renewable binder in sustainable geopolymer offers a valuable approach for recycling geopolymer waste. This study investigated the micro-macro characteristics of fly ash (FA)-based geopolymer, including the replacement of FA with GWP up to 100%. The GWP comprised the GWPG from GGBS-based geopolymer paste, the GWPGF from GGBA-FA-based geopolymer paste, and the GWPF from FA-based geopolymer paste, respectively. The findings revealed that GWPG exhibited higher alkaliactivated reactivity compared to GWPGF and GWPF. The geopolymer made with 100% GWPG demonstrated a better microstructure than FA-based geopolymer, but the microstructure of geopolymer deteriorated with the inclusion of GWPGF and GWPF. The average pore diameter of geopolymer made with 100% FA, 100% GWPG, 100% GWPGF, and 100% GWPF was measured at 18.06, 15.69, 116.50, and 92.62 nm, respectively. Mixing GWP led to an increase in drying shrinkage. The strength and permeability resistance of eco-friendly geopolymer initially decreased and subsequently improved with increasing substitution of GWPG, with geopolymer made with 100% GWPG exhibiting superior strength and permeability resistance compared to FA-based geopolymer. However, the strength and permeability resistance of eco-friendly geopolymer exhibited a continuous decline with the increasing replacement of GWPGF or GWPF, up to 100%. When the content of GWP was identical, GWPG blended geopolymer exhibited superior micro-structure and macro-properties compared to GWPGF or GWPF blended geopolymer. Thus, it is recommended to substitute GWPG for 100% FA in fully recycled geopolymer owning good strength and permeability resistance. However, caution should be exercised when incorporating high volumes of GWPGF or GWPF in eco-friendly geopolymer.