To study the nucleation and crystal growth processes, a titration system (OMNIS, Metrohm) equipped with two automatic burettes (Dosing unit, 20 mL), pH (Unitrode) and a calcium ion selective electrode (combined polymer membrane electrode) was used. To enable a constant solution temperature of 25.0 ± 0.1 • C, an in-house built double jacketed reaction vessel with a capacity of 250 mL coupled to a thermostat (JULABO 200F) was used. To avoid carbonation during the experiment, the reaction vessel was closed with a lid with openings for the electrodes, and a gentle flow of dry nitrogen was applied to the solution's surface. The pH electrode was calibrated daily using three standard buffers, pH 4, 7, and 10 (Chemsolute, Th. Geyer). The calibration of the calcium ion-selective electrode (ISE) was repeated three times before each nucleation experiment by dosing CaCl 2 solution (0.5 mol L -1 for CH, 0.03 mol L -1 for C-S-H) into 150 mL water (100 mL water + 20 mL NaOH (1 mol L -1 ) for C-S-H).