For pore solution analysis, samples were drawn from the suspension at different hydration times and subsequently filtered through a syringe filter with a pore size of 0.22 µm. Immediately after filtration, 0.5 mL of the filtrate were mixed with 0.2 mL nitric acid (6 M) and 9.3 mL ultrapure water, resulting in acidification to prevent precipitation and dilution of the filtrate by a factor of 20. Calibration solutions for calcium and aluminum determination were prepared with concentrations of 0.1, 1.0, 10.0, and 50.0 mg/L by diluting a multi-element standard (1000 mg/L, calibration standard IV, VWR Chemicals).