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

Abstract

AbstractAiming 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.