Calculated XRD patterns of (a) jennite and (b) tobermorite. Indexing (non-exhaustive) was performed using models from Bonaccorsi et al. (2004) and Merlino et al. (2001). Basal reflections are omitted. For each mineral, the theoretical XRD patterns (from top to bottom) of an ordered form having a mean CSDab size of 20 nm, and from disordered variations having a CSDab size of 20, 10 and 3 nm are presented. Grey areas correspond to the regions where Taylor (1986) identified the overlapping tobermorite and jennite diffraction maxima.