The influence of silicon on the formation and transformation of corrosion products

Accurate model predictions of corrosion-driven damage in reinforced concrete structures necessitate a comprehensive understanding of the rate of corrosion product formation. Here, we investigate the influence of dissolved Si characteristic of cementitious systems on the rate of corrosion product transformation at alkaline pH. Compared to systems aged in the absence of Si, small amounts of Si decrease the formation rate of the thermodynamically stable corrosion product goethite by a factor of 10. The estimated first order rate constant of transformation $k$ decreases exponentially as a function of the dissolved Si concentration and follows the progression ${\text{log}}_{10}k={\text{log}}_{10}{k}_0-$ 14.65×[Si]${}^{0.28}$. Findings further suggest that the observed retardation is primarily due to the formation of a mobile aqueous Fe-Si complex. The concentration of Si in cementitious systems has a crucial influence, and additional research is required to fully incorporate this factor into reactive transport models, ultimately essential for accurate service life predictions.