Chemo-physical Analysis on Corrosion Initiation of Offshore Structures under Chloride Attack

Abstract

Chloride ingress has been recognized as a main factor inducing the corrosion of offshore reinforced concrete structures. It is acknowledged that the chemical attack can lead to concrete property deterioration, which inevitably affects the reinforcement corrosion. Herein, the influence of the concrete aging on the chloride-induced corrosion initiation is systematically evaluated by a novel numerical framework. In this framework, the chemo-physical analysis is conducted based on coupled NernstPlanck model and Gibbs energy minimization model. The proposed method is first validated against reported experimental results. It is found that the chloride ingress is always accompanied by leaching of hydrates near the exposure surface, leading to the porosity enlargement. Moreover, due to chemical binding of chloride to monosulfoaluminate, ettringite continuously precipitates under the function of released sulfate ions. Through a series of numerical analyses, it is revealed that the newly formed hydrates impose competitive effects on chloride transportation due to the simultaneous pore-clogging and expansion-induced microcracks. Chloride-induced corrosion occurs earlier in the situation that the effect of microcracks overcomes that of pore clogging, otherwise, the corrosion is delayed.

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