Whatever activators used, increasing the quantity of Na2O led to acceleration and intensification of hydration, as previously observed in the literature . More in detail, in the case of NaOH activation (Figure and), two hydration peaks appeared at 8 and 10 hours for activation with 2 wt% Na2O, while a single broad peak was visible with a maximum at 6 h for cements with 4 or 6 wt% of Na2O. Therefore, increasing the amount of Na2O would thus lead to an acceleration of the two stages that were hypothesized above (see section Hydration kinetics of the alkali-activated slag pastes), which then fully overlapped. The total heat measured increased with the concentration of activator, which is the sign of a higher degree of hydration. Furthermore, these observations are in line with those made in the Vicat prisometry (Figure in Supplementary Materials), where an acceleration of the onset of setting was observed with increasing activator quantity.