Impact of the solidification path of FeO_x–SiO₂ slags on the resultant inorganic polymers

Abstract

Aiming to reduce the carbon dioxide emissions associated with cement production, alternative binders such as inorganic polymers currently receive substantial attention and slags from the non‐ferrous metallurgy are promising precursors. However, studies that correlate their chemistry and crystallinity with the newly formed binder remain limited. In this work, the effect of three different solidification methods on glass formation and reactivity of FeOx–SiO2 slags, as well as on the molecular structure of the resultant Fe‐rich inorganic polymers, was investigated. The inorganic polymers were synthesized by mixing the slags (approximate molar ratio FeO/SiO2 = 1.6) with an alkali silicate solution (molar ratios SiO2/Na2O = 1.6 and H2O/Na2O = 25). Results demonstrated that higher cooling rates promoted higher glass formation and faster reaction kinetics when the slags were activated. 57Fe Mössbauer spectroscopy indicated that all the slags consisted predominantly of Fe2+ ions with a minor amount of Fe3+ ions, regardless of the variability in glass content. The binder phase of all inorganic polymers consisted of iron in both Fe2+ and Fe3+ states, after 28 days of curing. After pulverizing the inorganic polymer pastes and exposing the powder to air for 28 additional days, the Fe2+ state in the binder transformed to Fe3+. The compressive strength evolution of the three slags showed that the 2‐day strength was higher for the samples with a higher amorphous fraction, while after 28 days, this influence was less pronounced.

Development of Sustainable Alkali-Activated Mortars Using Fe-Rich Fayalitic Slag as the Sole Solid Precursor

“…The chemical properties of the slag are influenced by its cooling process and cooling rate. Slowly cooled FS results in a hard, crystalline product, while the water cooling of FS enhances quick solidification, resulting in an amorphous/glassy slag (Fan et al, 2014;Siakati et al, 2020). Water-cooled FS comes in a granular form with particle sizes ranging from 0 to 4 mm, and its production has continued to rise yearly with the increasing demand for nickel and copper (Michailova and Mehandjiev, 2010).…”

Unraveling the nano-structure of a glassy CaO-FeO-SiO2 slag by molecular dynamics simulations

“…The final properties are largely controlled by the intrinsic characteristics of the slags (e.g. chemical composition, mineralogy and nano-structure) [4][5][6][7][8], which are determined by the production process [9,10]. Consequently, an accurate knowledge of the nano-structure of the slags is of paramount importance as this information can be linked to the reactivity of the slag during alkali activation and the final performance of the resulting IPs.…”

The state of Fe3+ in the C–F–A–S–H system with varying Fe/Si and Ca/Si ratios

“…Similar QS values have also been reported in the amorphous content of FeO X –SiO 2 slag and its consolidating products. 65 Further investigation regarding this kind of Fe 3+ will be carried out in future work.…”