The mechanism presented here is in agreement with the literature results, even though the products formed are not always identical . This is particularly true if the minor hydration products that depend strongly on the chemical composition of the slag. Indeed, Bernal et al. first saw the formation of different polymorphs of calcium carbonate, zeolite NaA Na12Al12Si12O48.18H2O and gaylussite. However, the NMR and XRD results show a silicate phase too amorphous to be a zeolite, which we attributed to N-A-S-H. Moreover, the formation of gaylussite only happens after a few days in our samples. 29 Si CPMAS NMR spectra of the slag cement pastes.