Finally, another resonance was added at -76.1 ppm to fit the spectra. This contribution could be assigned to Si in Q1 environments (Q1(I)) that were charge-balanced by different ions from the Si corresponding to the resonance at -79.0 ppm (Q1(II)) . Some authors have suggested that Q1(I) corresponds to tetrahedra charge-balanced by Ca 2+ while those that give the resonance Q1(II) are charge-balanced by Na + or H + , leading to more shielding due to their electronegativity . The same resonances (Q1(I), Q1(II), Q2(1Al), Q2 b and Q2 p ) were observed in the spectra for NaOH-activated slag pastes (Figure ) at total heats above 23 J/g, except for the contribution corresponding to the Q3 and Q4 environments. In addition, no hydration products could be detected at the first stop (0.5 J/g) for NaOH-activated pastes.