Utilization of Ferronickel Slag as Additive in Portland Cement: A Hydration Leaching Study

The present study reports the properties and hydration of blended cements with ferronickel slag, produced during the pyrometallurgical treatment of laterites for the production of ferronickel. For that purpose, the slag was ground to a specific surface area of 4,000 cm(2)/g and added in ratios 5, 10, 15, and 20 wt%. The produced blended cements were tested by determining their initial and final setting times, standard consistency, flow of normal mortar, expansibility and compressive strength at 2, 7, 28 and 90 days. X-ray diffraction and TG/DTG analyses were used for the determination of the hydration products, whereas the microstructure of the hardened cement pastes and their morphological characteristics were examined by scanning electron microscopy. The blended cements leachability behavior was determined by the toxicity characteristic leaching procedure test and the tank diffusion test for monolithic samples (NEN 7375). The results revealed that the concentrations of leached heavy metals were substantially below the regulatory thresholds. According to the results, the ferronickel slag could be readily utilized as cement additive, presenting environmental benefits in waste management practice.