Synthesis and characterization of iron and aluminum-containing AFm-phases

 
The cement industry accounts for 8% of the global CO2 emissions, but their impact on the greenhouse effect results in growing social awareness. Therefore, CO2 footprint becomes a product selection choice, and substituting Portland cement with a lower CO2-footprint alternative binder is sought [1]. In this context, new hydraulic binders have been studied as a potential Ordinary Portland Cement substitute. Many of them are composed of iron oxides and aluminum oxides, present in Ca4Al2-xFe2+xO10-like phase and forming Ca-LDH (i.e. AFm; structure described in Figure 1) as a hydration product. It has become essential to study the possible existence of Fe/Al AFm solid solutions in order to characterize the hydration process properly. Ca2Al2-xFex(OH)6.X.nH2O layered AFm samples intercalated with either nitrate, chloride, or carbonate X anions were synthesized by the co-precipitation method with varying the Fe/Al molar ratios. The experimental conditions were optimized to make possible the formation of Al-AFm and Fe-AFm using the same parameters (namely pH value) [2]. Rietveld refinements were performed to demonstrate the existence of a solid solution between the two trivalent metallic end members, and spectroscopic analyses were used to confirm the intercalation of the targeted anion.