two resonances corresponding to tetrahedral environments with isotropic chemical shifts of 73.2 ppm (σ = 0.5 MHz) and 63.0 ppm (σ = 0.2 MHz), and one resonance at 11.5 ppm (σ = 0.3 MHz) assigned to an octahedral environment. An 27 Al resonance at 73.2 ppm dominated the spectrum and corresponds to the tetrahedral site generally observed in slag and in percalcic aluminosilicate glasses . The second minor tetrahedral resonance at 63 ppm is probably the sign of the presence of a very small quantity of slag hydrated in the form of amorphous alumina-silicate gel.