Atomic-Level and Surface Structure of Calcium Silicate Hydrate Nanofoils

Z Casar and AK Mohamed and P Bowen and K Scrivener, JOURNAL OF PHYSICAL CHEMISTRY C, 127, 18652-18661 (2023).

DOI: 10.1021/acs.jpcc.3c03350

Deciphering the calcium silicate hydrate (C-S-H) surface is crucial for unraveling the mechanisms of cement hydration and property development. Experimental observations of C-S-H in cement systems suggest a surface termination which is fundamentally different from the silicate- terminated surface assumed in many atomistic level studies. Here, a new multiparameter approach to describing the (001) basal C-S-H surface is developed, which considers how the surface termination affects the overall properties (Ca/Si ratio, mean chain length, relative concentration of silanol and hydroxide groups). Contrary to current beliefs, it is concluded that the (001) C-S-H surface is dominantly calcium terminated. Finally, an adsorption mechanism for calcium and hydroxide ions is proposed, which is in agreement with the surface charge densities observed in previous studies.

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