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Corrosion of Rebars in Simulated Concrete Pore Solutions with the Presence of Chloride Ions
Abstract
Steel rebar is widely applied in reinforced concrete (RC) structures due to its significant improvements in mechanical properties. Bridges, for example, contain a large portion of rebar consumption and therefore, the performance of rebar becomes very important for evaluating integrity, durability, and sustainability of RC structures. Considering the alkaline environment of rebar in RC, rebar normally remains in a passive state but the ingress of chloride ions may cause passivity breakdown, corrosion acceleration, and eventually unexpected failure. Therefore, chloride induced corrosion has drawn lots of attention in the research field and this study focuses on evaluate the corrosion performance of different types of rebar with information including chloride threshold value (CT) and long-term degradation performance.
In this study, rebar with different chromium contents and galvanized coatings was examined in simulated concrete pore solution (SCPS) with the presence of NaCl and then evaluated by a variety of electrochemical and post-characterization analyses, including open circuit potential (OCP), linear polarization resistance (LPR), electrochemical impedance spectroscopy (EIS), cyclic polarization (CP), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS).
CT values of rebar with chromium contents (0, 4, and 23%) were generated after applying Mixed Potential Model (MPM) and showed relatively good consistency with the experimentally obtained values, published values from other researchers, and therefore could serve as reference values for RC structure maintenance.
For the long-term performance evaluation results, the additional Cr content is proven to mitigate the localized attacks and therefore, is able to reduce the probability of unexpected failure. Additionally, the galvanized coatings were found to provide sufficient protection by acting as a barrier and sacrificing as an anode up to 12 months of immersion. The passive-to-active transition states for coatings were also identified.
This work determined the chloride threshold values of Cr-based rebar materials, evaluated the relative long-term corrosion performance of carbon steel, 9%Cr steel, and galvanized steel rebar. This work contributes to a better understanding of corrosion performance of steel rebars, helps the current maintenance work of existing in-service rebar, and provides feedback for new rebar design with better corrosion performance.
Subject
Rebar corrosionchloride ions
simulated concrete pore solution
long-term immersion
chloride threshold
Citation
Lu, Yi (2022). Corrosion of Rebars in Simulated Concrete Pore Solutions with the Presence of Chloride Ions. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198734.