Nanoindentation analysis of corrosion products and induced expansion stress in reinforced concrete exposed to marine environments

Abstract

Reinforced concretes are widely used in construction owing to their ultrahigh mechanical properties and long-term durability. However, the corrosion of steel bar within concrete poses a substantial threat to the structural integrity of buildings, impeding advancements in ocean engineering and necessitating expensive maintenance measures. In this study, the corrosion mechanisms of reinforced concrete under marine environments were investigated. The elastic modulus of corrosion products and the identification of rust compositions in different corrosive environments were comprehensively investigated using nano indentation technique and microscopic characterizations. The average young's modulus of rust products in chloride, sulfate, and chloride-sulfate composite solutions were measured to be 47.6 GPa, 37.59 GPa, and 61.52 GPa, respectively. And the analysis identified the presence of two distinct layers of rust product, providing valuable insights into the corrosion process. In addition, the real-time and in-situ monitor of corrosion expansion stress shows that the rust expansion stress generated in chloride solution was almost twice as high as that under sulfate solution and 1.3 times higher than that in the composite solution. The advanced wire beam electrode technique was employed to compare and analyze the different stages of depassivation, pitting corrosion and corrosion rate during the whole process. The corrosion process under chloride solution showed larger and more serious corrosion than under sulfate solution, with the anodic peak current spreading and reaching 4.00 μA cm-2 after 300 days. This work reveals valuable insights into the corrosion behaviour of reinforced concrete in three corrosive conditions and can be used to inform the development of strategies for corrosion prevention and mitigation.