A ground granulated blast-furnace slag supplied by CHRYSO Saint-Gobain Construction Chemicals was used in this study. The same slag was used in our previous study of superplasticizers efficiency in slag pastes but its characteristics are nevertheless recalled here for clarity. Its chemical composition, determined using X-ray fluorescence (XRF) by an external contractor (Université Paris Cité, France), is summarized in Table . A specific surface area of 0.85 ± 0.02 m 2 /g was measured by krypton adsorption following the BET method (see below). Figure presents the particle size distribution of the slag dispersed in isopropanol and measured by laser light diffraction (Mastersizer, Malvern Panalytical), courtesy of Dr. Y. Keskin (Navier laboratory, Marne la Vallée, France), with a Dv50 value of 9.15 μm. The particles had irregular shapes with sharp edges, as shown on the SEM image (Figure ). The image was taken on a JEOL 6300F field emission electron microscope, at 10 kV, in high-vacuum mode. NaOH and Na2CO3 were dissolved in ultrapure (Type III) water (conductivity of less than 18.2 mΩ/cm) in the appropriate amounts, in order to obtain an alkaline solution with the target activator's concentration (wt% of Na2O per mass of slag). In the case of the sodium silicate activation, Betol 52T was diluted with ultrapure water and a specific quantity of NaOH was dissolved to reach the desired SiO2/Na2O molar ratio. Except otherwise stated, the activating solutions had a composition corresponding to a paste formulation of 4.0 wt% Na2O by weight of slag, a water/slag (w/s) weight ratio of 0.4 (including the water from the activator), and for sodium silicate activation a SiO2/Na2O molar ratio of 1.7 (Na2Si1.7O4.4).