Electrochemical Model Of Corrosion Rate Of Steel Bars Embedded In Concrete In Different Corrosive Environments

Steel corrosion has drawn extraordinary concern in durability of concrete structures. A precise model for corrosion rate of steel bars embedded in concrete will prove the theoretical basis and reference for design, construction and assessment. To accomplish this, based on the theory of metal corrosion, a model for corrosion rate of steel considering various corrosive environment was proposed in this thesis. The content includes:(1) Experimental study of anti-erosion ability of modern concrete. The influence of mineral admixture (slag and fly ash) on the resistance of concrete to chloride ingress was analyzed by natural diffusion method and ASTM C1202. While the influence of mineral admixture on the resistance of concrete to carbonation ingress was studied by accelerated carbonation experiment.(2) Modeling corrosion rate of steel bars embedded in concrete. Based on the theory of metal corrosion, a electrochemical model for corrosion rate of steel bars embedded in concrete was built, and the influence of humidity, electrical resistivity of concrete and anode-to-cathode ratio on corrosion rate was analyzed. To verify the proposed model, corrosion tests in different environmental conditions (accelerated carbonation, chloride added to raw materials and chloride ingress by solution) were carried out by measuring the rebar potential and corrosion current density change of three kinds of specimens.(3) Model for corrosion rate of steel bars under 2-D oxygen diffusion condition. According to the state of steel bars embedded in concrete, this corrosion model based on 2-D oxygen diffusion aims to provide a theoretical basis for determination of the modified coefficient of steel bar position. Experiment studying the influence of concrete cover depth, steel diameter, position and type of steel bars on corrosion rate was carried out to verify the proposed model. Comparison of results showed that the proposed model was in better accordance with the real state than traditional 1-D oxygen diffusion model.The research was financially supported by National Basic Research Program of China (973 Program) (Grant No.2009CB623200), National Natural Science Foundation of China (Grant No. 50838008), National Natural Science Foundation of China (Grant No.51008272).