For the C-S-H nucleation experiments, the inhibiting effect is investigated via the inhibiting factor (IF) calculated from the calcium measured at the nucleation onset (equation 5): the saturation index cannot be calculated in that case due to the fact, that we only measured pH and Calcium ion concentration continuously, while the silicon concentration was determined via ICP-OES for samples every 0.25 mmol L -1 . A continuous measurement of silicon would be required to accurately calculate the saturation index vis-a-vis the C-S-H phase.