Mechanistic study on initial passivation and surface chemistry of steel bars in nano-silica cement pastes

This work studied the passivation of steel bar in cement pastes prepared with and without nano-silica by using electrochemical measurements and surface characterization methods. The results showed that the passivation of steel bar in cement paste was dominated by the chemistry of the pore solution and the evolution over time, which are closely associated with the hydration process of the cement. The addition of nano-silica influenced the alkalinity of the pore solution in cement paste and modified the pore structure of the cement paste, which resulted in a different passivation process and a thicker passive film with a higher proportion of Fe²⁺ oxides. The intrinsic corrosion resistance of steel bars in concrete prepared with nano-silica was expected to be enhanced.