Geopolymerisation of low calcium ferronickel slags

The present experimental study investigates the feasibility of geopolymer synthesis from low Ca electric arc ferronickel slags. Additives used include kaolinite, sodium silicate, sodium hydroxide and water. The effect of the main factors considered (heating temperature, heating time and aging period) as well as of their interactions on the final compressive strength of the geopolymers produced was studied through a 2(3) factorial design. The experimental results and the variance analysis have shown that only aging period has a statistically very significant and positive effect on the final compressive strength while the effect of the other factors as well as of their interactions were either less significant or negligible. Identification of new phases formed in order to elucidate geopolymerisation mechanisms was carried out by XRD and FTIR. Sodalite, maghemite, thermonatrite, trona and calcite are the major phases identified. The structural integrity of the produced geopolymers was studied by subjecting them to accelerated freeze-thaw cycles. Finally, the durability of the produced geopolymers when immersed in various aquatic and acidic solutions was investigated.