Correctly assessing the influence of sodium citrate on portlandite nucleation
Marie Collin, Andreas Vohburger, Torben GädtAbstract
Despite extensive application in cementitious systems, the mechanisms by which citric acid influence distinct cement hydration reactions, such as portlandite nucleation, are not yet fully understood. In this study, the effect of citric acid on the kinetics of portlandite nucleation was investigated using calcium‐selective electrode measurements and thermodynamic modelling. The ability of citrate to precipitate as a calcium salt and to complex the remaining calcium in solution significantly delays the nucleation of portlandite. Furthermore, the formation of additional unidentified calcium species was observed, leading to a further decrease in calcium activity in solution. These findings highlight the need for additional research on highly supersaturated portlandite systems.