Modelling transport and precipitation of corrosion products in cementitious materials: A sensitivity analysis

Abstract

Corrosion of steel in concrete is a common degradation mechanism. With the growth of corrosion products, expansive pressure is created that may damage the concrete. In conventional studies, corrosion products are assumed to precipitate on the steel surface and from there, exert stresses on the surrounding concrete. However, before precipitating, the released ferrous ions can penetrate into the concrete. This means that corrosion products are not necessarily formed immediately after the dissolution of iron. Instead, the formation of corrosion products can be viewed as kinetic processes, which has been already studied in aqueous solution, depending on oxygen concentration, pH, ferrous ion concentration, etc. In our previous studies, a reactive transport model was proposed, which includes the processes of iron dissolution, ferrous ion diffusion, oxidation, and precipitation of ferrous and ferric compounds. In this paper, the First Order Reliability Method (FORM) was used to analyze the sensitivity of the different model parameters, such as ferrous ion oxidation reaction rate, ferrous hydroxide precipitation rate, tortuosity, and constrictivity. The results show that the tortuosity factor is the most dominant parameter, followed by ferrous ion oxidation reaction rate and constrictivity, which have an equal sensitivity. Ferrous hydroxide precipitation rate is not sensitive regardless of its reference value. In addition, we found that the sensitivity of tortuosity factor increases with its reference value and the corrosion rate does not affect the sensitivity of studied parameters.