Chemistry of iron in cementitious systems : impact of Calcium and particle size on Iron(III) solubility and speciation

In the context of waste disposal in rock salt formations, the corrosion of cementitious wastes has been reported to potentially generate CaCl2-rich brines in combination with high pH values. Previous studies with various metals in alkaline, concentrated CaCl2 systems have shown the formation of highly hydrolyzed moieties stabilized by Ca2+. Therefore, the formation of ternary complexes Ca-Fe(III)-OH is expected. On the basis of well-defined Fe(III) oxo-hydroxide solid phases (ferrihydrite, goethite) solubility experiments were conducted in CaCl2 solutions. The aqueous speciation was investigated via EXAFS analysis. Factors increasing the solubility (i.e., complexation with calcium and crystal size) and their impact on the stability fields of iron corrosion phases will be discussed.