Hydration Degree of Alkali‐Activated Slags: A 29 Si NMR Study

A commercial blast furnace slag was activated using either sodium hydroxide or hydrous sodium metasilicate, and the degree of hydration was determined by 29 Si magic angle spinning nuclear magnetic resonance ( NMR ). The results are compared with measurements made using scanning electron microscopy image analysis ( SEM ‐ IA ). The results from both 29 Si NMR and the SEM ‐ IA measurements indicated a fast initial reaction with the alkali, and similar degrees of hydration throughout the reaction. The 29 Si NMR results were analyzed using two different methods for fitting the residual slag in the decomposition of the 29 Si NMR spectra: the first method used the spectrum of the anhydrous slag, whereas the second method used the spectrum of the dissolution residue of the hydrated sample. Only the first method provided a satisfactory simulation. The degree of hydration and the Al/Si atomic ratio within the C–S–H , deduced by 29 Si NMR were in agreement with SEM ‐ IA and EDX analyses.