Structure, dynamics and mechanical properties evolution of calcium-silicate-hydrate induced by Fe ions: A molecular dynamics study

The adsorption of Fe ions in the calcium-silicate-hydrate (C-S-H) is of great importance as it involves the corrosion process of reinforced concrete structures. In this paper, molecular dynamics simulation was carried out to study the structure, dynamics and mechanical properties evolution of C-S-H induced by Fe ions. Through the analyses of local structure, atomic dynamics and bond stability, the results show that Fe ions are in tetrahedral coordination in the C-S-H and form 3 shells with neighbor atoms which are consistent with the extended X-ray absorption fine structure (EXAFS) results. In addition, the incorporation of Fe ions could reduce the polymerization of silicate chains by disordering the distribution of Os and Si atoms and weakening the strength of Si-O bonds. On the contrary, the connection between Caw (inter layer Ca atoms) and O atoms was slightly enhanced by Fe ions. The mechanical properties of C-S-H in three directions all decrease with the increasing Fe/Ca ratios (i.e., corrosion degree) as the silicate chains and interlayer connection were weakened by Fe ions. Hopefully, the properties of Fe ions adsorbed in the C-S-H could provide new insights on understanding and predicting performance of concrete structure under corrosion environment. (c) 2021 Published by Elsevier Ltd.