Influence of ferronickel slag 4 powder on the properties of Class C fly ash based geopolymer paste

This study examined the performance of a geopolymer paste based on class C fly ash and ferronickel slag under ambient curing conditions. To achieve an excellent geopolymerization mechanism between silica and alumina, the ferronickel slag was ground intensively using a ball mill to achieve a similar fineness to class C fly ash. Ferronickel slag four powder (FNS 4P) was added to the geopolymer paste comprising class C fly ash up to 20% in 10% increments. Na2SiO3 and NaOH 14 M were blended in a 2:1 ratio to create the alkaline activator, which was ready 24 hours before mixing. As class C fly ash hardens quickly after being mixed with an alkaline activator at a temperature of more than 25 °C, the mixing process was conducted in the morning. Performance analysis was investigated in this study using setting time, compressive strength, and flexural strength. The results reveal that the compressive strength of geopolymer paste containing FNS 4P slightly increased compared to the reference mixture at 28 days of ambient curing. The flexural strength of the mixture containing 20% FNS 4P increased in the early days of curing. However, the positive effect of FNS 4P in flexural strength performance was only for a mixture containing 10% FNS 4P after curing at 28 days. The addition of FNS 4P delayed the setting time of fresh geopolymer paste containing C-class fly ash.