The use of superabsorbent polymers as internal curing agents in high performance concrete has gained much interest in research and slowly gaining interest among industrial producers. Although there have been many publications on the microstructure of internally cured system, little interest has developed in the actual mechanisms of absorption and desorption of superabsorbent polymers in high pH systems and how they are related to the structure of the polymers themselves. Results in the literature indicate that the polymer structure actively interacts with the ions present in the solvent, which results in a strong ion filtration effect. This paper demonstrates that this ion filtration effect is due to electrostatic interaction. The timing and dominance of this effect can heavily influence the effectiveness in internal curing. In particular, concrete containing superabsorbent polymers demonstrate different strength gain behaviors when cured in lime-saturated water. --------------------------------------------------------------------------------