Seawater-mixed alkali-activated materials: a comparative investigation of metal slag suitability

Abstract

Ferronickel slag (FNS) and blast-furnace slag (BFS) were investigated to see the effect of seawater mixing. The metal slags were activated with potassium hydroxide solution, and seawater collected from two different locations was used to produce the samples. Deionized water-mixed FNS and FNS-BFS blend pastes produced layered double hydroxide (LDH) phases such as Mg-Al LDH, Mg-Fe LDH, and Ca-Al LDH. When seawater was used, the LDH phases intercalated with chloride ions to produce Mg-Al-Cl LDH, Mg-Fe-Cl LDH, and Ca-Al-Cl LDH. No reduction in strength with time was observed due to the use of seawater. Regardless of the mixing water type, partial replacement of FNS by BFS yielded higher strength than a single FNS precursor in alkali activation; the major contributors to strength performance were C-S-H, C-S-H(I), and C-A-S-H. Greater early strength was developed using seawater in FNS-BFS blend pastes, probably due to greater dissolution of the precursors by seawater.