Alkali Activation of Metallurgical Slags: Reactivity, Chemical Behavior, and Environmental Assessment

Abstract

Alkali-activated materials (AAMs) represent a promising alternative to conventional building materials and ceramics. Being produced in large amounts as aluminosilicate-rich secondary products, such as slags, they can be utilized for the formulation of AAMs. Slags are partially crystalline metallurgical residues produced during the high temperature separation of metallic and non-metallic materials in the steelmaking processes. In the present study, the electric arc furnace carbon or stainless steel slag (EAF) and secondary metallurgical slag such as ladle furnace basic slag (LS) were used as precursors in an alkali-activation process. EAF slag, with its amorphous fraction of about 56%, presented higher contents of soluble Si and Al species with respect to ladle slag R (35%). However, both are suitable to produce AAM. The leaching behavior shows that all the release values are below the regulation limit. All the bivalent ions (Ba, Cd, Cu, Ni, Pb, and Zn) are well immobilized in a geopolymeric matrix, while amphoteric elements, such as As and Cr, show a slight increase of release with respect to the corresponding slag in alkaline and aqueous environments. In particular, for Sb and As of AAM, release still remains below the regulation limits, while Mo presents an increase of leaching values that slightly exceeds the limit for landfill non-dangerous waste.

Antibacterial Properties and Cytotoxicity of 100% Waste Derived Alkali Activated Materials: Slags and Stone Wool-Based Binders

“…This behavior confirmed the immobilization efficiency of the alkali activated materials comparing the amount of the leachable amount of the element from the geopolymer structure in water as already observed for alkali activated materials containing wastes (Kiventerä et al, 2018). GP-MgO-rich showed an increase of Mo according to literature (Lancellotti et al, 2021). The same immobilization behaviour characterized the other alkali activated materials, GP-CaO-rich, GP-CaO-rich-BAS, GP-CaO-rich-NC, except for Cr that increased after the alkaline activation, but it remained lower than the law limit.…”

A Review of Circular Economy Prospects for Stainless Steelmaking Slags

“…3 The scheme of different unit processes in stainless steelmaking, slags formation, treatment, and product applications already discussed above. The use in fillers for instance as an ingredient in asphalt concrete has been studied [71,72]. Precipitated calcium carbonate (PCC) is a relatively valuable product as a filler and pigment for paper industry.…”

Influence of Sintering Temperature of Kaolin, Slag, and Fly Ash Geopolymers on the Microstructure, Phase Analysis, and Electrical Conductivity

“…Several studies were conducted to identify an alternative material which possesses outstanding thermal stability and fire resistance in elevated temperature. Geopolymers are an amorphous three-dimensional (3D) aluminosilicate system, which was synthesised at ambient or slightly higher temperature by alkaline activation of suitable precursor raw material from industrial waste, fly ash [ 2 , 3 , 4 , 5 , 6 ], slag [ 7 , 8 ], and kaolin [ 9 , 10 ]. It was shown that these inorganic materials that were identified, delivered an exceptional performance at elevated temperatures.…”