Interaction of layered double hydroxide phases with chloride ions

For the sustainable transition of the construction sector, the durability of cementitious materials needs to be guaranteed. This requires a fundamental understanding of the deterioration mechanisms for example how the ingress of potentially detrimental ions affects the composition of the pore solution as well as the phase assemblage. This contribution links results from several research projects investigating the changes in layered double hydroxides (LDH) composition upon exposure to chlorides. The Cl/Al ratio in chloride‐containing AFm phases depends on the chloride concentration as well as on the pH of the liquid phase. In addition, the amount of AFm phases is affected by the pH. Another member of the LDH group, hydrotalcite (Ht), can also incorporate chloride ions into the interlayer and exhibit a similar chloride‐binding capacity as stoichiometric Friedel's salt. However, the chloride‐binding capacity of Ht also depends on the composition of the pore solution. These findings aid the fundamental understanding of chloride‐binding mechanisms of cementitious materials. This is especially important, as the pH and calcium availability in the pore solution of hydrated cement may be altered during its service life. Moreover, the results may help to accurately predict the durability performance of samples in the laboratory.