Most of the fundamental knowledge about the C-(A)-S-H structure derives from the coupling of solid-state nuclear magnetic resonance (NMR, mainly Si, Al and 1 H) and atomistic simulations . The Ca/Si ratio in C-(A)-S-H (1.4-2.0) is substantially higher than in tobermorite (0.83) due to incorporation of Ca in the interlayer and Ca adsorption at the surface . In lowcarbon cements, the incorporation of Al in C-(A)-S-H is of particular interest due to the presence of alumina-bearing SCMs (fly ash, calcined clays, natural pozzolans) in the cement mixture. It has been shown that Al is incorporated in vacant silicate-bridging sites, stabilized by hydroxyl groups and Ca in the interlayer .