CONTRIBUTION OF H-1 COMBINED ROTATION AND MULTIPULSE SPECTROSCOPY NUCLEAR-MAGNETIC-RESONANCE TO THE STUDY OF TRICALCIUM SILICATE HYDRATION

Hydration products of tricalcium silicate (C3S) are the calcium silica te hydrates (C-S-H) and portlandite. Silica fume, added to anhydrous c ement in industrial formulations, reacts with portlandite and leads to C-S-H slightly different from the previous one (this reaction is call ed the pozzolanic reaction). C3S hydration at 120 degrees C With and w ithout silica fume has been studied by two H-1 nuclear magnetic resona nce techniques: combined rotation and multipulse spectroscopy (CRAMPS) and magic angle spinning (MAS). The static spectra are broadened by t he proton-proton dipolar interaction. The H-1 MAS technique does not a llow us to remove the effects of this interaction completely and canno t be in this case a quantitative method. Therefore the CRAMPS techniqu e, which can remove the broadening of the interaction because of the u se of a multipulse sequence associated with the sample rotation, was u sed. It is shown that the CRAMPS NMR spectra allow us to describe the action of silica fume on the hydrates and to reveal the competition be tween portlandite formation around the C3S grains and portlandite diss olution near the silica grains until the complete dissolution of portl andite.