Understanding the improvement of Mg-rich electrical ferronickel slag on magnesium potassium phosphate cement's performance

Electrical ferronickel slag (EFS), a Mg-rich slag from nickel-iron alloy production, is conventionally recycled by blending it with Portland cement as mineral admixtures. However, the low hydration activity of EFS will lead to severe negative effects on cement. To enhance the reuse value of EFS, this study comprehensively investigated the potential of using EFS in magnesium potassium phosphate cement (MKPC), from properties into hydration mechanisms. A variety of characterization techniques, combined with thermodynamic modelling, were applied. The results demonstrate that incorporating EFS effectively increases compressive strength and refines pore structure at all ages. This improvement is mainly attributed to the additional reaction of Mg2SiO4 and amorphous phases from EFS. Mg2SiO4 reacts at low pH and amorphous fractions are involved at higher pH to generate new products magnesium silicate hydrate M-S-H or magnesium aluminosilicate M-A-S-H gel. The findings will provide insight into the role of Mg-rich pyrometallurgical slags in MKPC systems.