Characteristics and reactivity of ferronickel slag powder

In this study, the hydration properties of a blended cement containing 30% ferronickel slag powder are investigated. The activities of electric arc furnace ferronickel slag (EFS) powder and blast furnace ferronickel slag (BFS) powder are both very low under non-alkaline conditions. Due to its higher CaO and Al2O3 contents and lower MgO content, the BFS powder exhibits higher pozzolanic activity than the EFS powder. The reaction of ferronickel slag in the cement decreases the Ca/Si ratio of the calcium silicate hydrate (C-S-H) gel and increases the degree of polymerization of the silicate chains. EFS powder tends to coarsen the pore structure of the hardened paste and decreases the compressive strength of concrete at any age; on the other hand, concrete containing the BFS powder exhibits a late-age microstructure and strength close to or even superior to that of plain cement concrete. Ferronickel slag powder improves the resistance of concrete to chloride ion penetration and the effect of BFS powder is more substantial.