Molecular dynamics study on bonding behaviors of γ–FeOOH/CSH interface under aggressive conditions

[Display omitted] •Water weakens the bonding of γ–FeOOH/CSH interface.•The Na+, Cl– and SO42– ions have different deterioration mechanisms on the γ–FeOOH/CSH interface.•Shear strength of the γ-FeOOH from CSH is reduced in aggressive environments. The steel fiber reinforced concrete structure exposed to the marine environment is vulnerable to the intrusion of water and aggressive ions, especially the interface between concrete and steel fibers, which affects their bonding behaviors and causes durability defects. In this paper, molecular dynamics simulation is used to elucidate the effects of water and ions on the bonding behaviors and mechanical responses of concrete and steel fiber interface under different environmental exposures. On the basis of the formation of CaCSH–Owater bonds and hydrogen bonds between water and CSH, aggressive ions further attract H2O molecules to CSH surface and occupy the coordination site between CSH and γ–FeOOH, leading to the reduction of their interaction energy and a decline in the bonding behaviors of the γ–FeOOH/CSH interface. The order of interfacial bonding deterioration degree affected by environment is NaCl + Na2SO4 > Na2SO4 > NaCl > Water > Dry. In the NaCl + Na2SO4 environment, the interaction energy of γ–FeOOH/CSH interface is reduced by 31.2 %, and the shear strength of γ–FeOOH has a reduction of 58.8 % compared with the dry environment.