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Alkali-activation of CaO-FeOx-SiO2 slag: Formation mechanism from in-situ X-ray total scattering
Tijdschriftbijdrage - Tijdschriftartikel
The pursuit of low-CO 2 technologies has led to a surge in research on alternative cementitious materials, of which alkali-activated materials are a large family. In recent years alkali-activated materials have expanded to encompass Fe-rich precursors in addition to the more commonly employed aluminosilicate precursors. The formation mechanism of alkali-activated materials from two Fe-rich synthetic slags has been assessed by employing in-situ X-ray total scattering and subsequent pair distribution function analysis. The evolution of the local atom-atom correlations reveals three reaction stages. After the dissolution of Fe-silicate clusters from the slag, a binder phase is formed with Fe in both Fe 2+ and Fe 3+ oxidation states. The Fe 2+ state is present in the form of trioctahedral layers, similar to those in Fe(OH) 2, while the Fe 3+ is likely located in the polymerized silicate network. Exposure to air causes the Fe 2+ species to transition to the Fe 3+ state.