Due to increasing interest in reducing CO2 emissions, new hydraulic binders are emerging, many of which contain significant amounts of iron and aluminum oxides. The reactivity of such binders can be activated using CaCl2. It thus appears essential to investigate mixed Al/Fe-Cl hydrates to better characterize the hydration products and hydration processes of these new hydraulic binders. AFm-Cl phases with varying proportions of Al3+ and Fe3+ trivalent cations were synthesized and characterized. Carbonation of AFm-Cl samples is unavoidable at ambient atmosphere and leads to phases with Ca2Al1-xFex(OH)6·Cl0.7(CO3)0.15·2H2O general composition (samples were synthesized for x = 0, 0.17, 0.33, 0.50, 0.67, 0.83 and 1). A complete solid solution between the two Ca2Al(OH)6·Cl0.7(CO3)0.15·2H2O and Ca2Fe(OH)6·Cl0.7(CO3)0.15·2H2O endmembers was demonstrated. Two hydration states were identified with characteristic interlayer distances of about 7.8 Å and 6.8 Å for, respectively, the Ca2Al1-xFex(OH)6·Cl0.7(CO3)0.15·2H2O hydrate and the Ca2Al1-xFex(OH)6·Cl0.7(CO3)0.15 dehydrated phase. Thermal studies indicated a similar succession of thermal events for Ca2Al1-xFex(OH)6·Cl0.7(CO3)0.15·2H2O regardless of the nature of the trivalent cation; the presence of iron however decreasing the degradation temperatures. Finally, the Ca2Al1-xFex(OH)6·Cl0.7(CO3)0.15·2H2O phase was investigated in the presence of carbonate anions, showing a progressive exchange of chloride for carbonate within the interlayer to form Ca2Al1-xFex(OH)6·(CO3)0.5·3H2O before degrading into calcite.