Fresh and hardened properties of geopolymer binder using ground high magnesium ferronickel slag with fly ash

The effect of using GFNS with fly ash in geopolymers was evaluated. Initial setting time decreased from 410 min to 188 min for 100% fly ash replacement by GFNS. The increases of SiO2/Al2O3 and MgO/Al2O3 ratios by GFNS accelerated the reaction to decrease setting time and workability. Le-Chatelier expansions were well below the recommended 5% limit. Soundness was not affected by GFNS since Mg was incorporated in the reaction product sodium magnesium aluminosilicate hydrate (N-M-A-S-H) as evidenced by the SEM images and EDS. No expansive brucite was found in XRD. A maximum 28-day compressive strength of 56 MPa was achieved in the ambient-cured geopolymer using 75% GFNS with 25% fly ash. This further increased to 64 MPa at 90 days which was also achievable by accelerated curing at 60 degrees C for 1 day. The amorphous N-M-A-S-H gel contributed to a denser microstructure and strength development by GFNS. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

The study evaluated the effect of using GFNS with fly ash in geopolymers, showing that GFNS can accelerate reaction rates, reduce setting time, and increase compressive strength. SEM images and EDS analysis indicated that the application of GFNS does not affect soundness, while the N-M-A-S-H gel contributes to the strength development of geopolymers.