This paper presents a continuation of studies into silicate anion structure using X-ray photoelectron spectroscopy (XPS). A series of C-S-H samples have been prepared mechanochemically, and then stored under ambient conditions for six months. Storage led to surface carbonation, the extent of which was dependent upon the calcium/silicon ratio of the fresh sample. Carbonation arose through decalcification of the C-S-H, leading to increased silicate polymerisation. The surfaces of the most calcium-rich phases (C/S = 1.33 and 1.50) underwent complete decalcification to yield silica (possibly containing some silanol groups) and calcium carbonate. Carbonation, and hence changes in silicate anion structure, was minimal for the C-S-H phases with C/S = 0.67 and 0.75.

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