The Corrosion Behaviour Of HRB400 Rebar In Simulated Concrete Pore Solution Containing Chlorine Salte

Reinforced concrete structure, which is the most important form of buildings in the world, is widely applied in every corner of human society. As the fundamental material that extensively applied in infrastructure construction, the durability of the reinforced concrete is concerned with the personal security and the life cycle cost of the buildings. In ideal service condition, the rebar in concrete is in passive state, so the performance degradation of the structure is a slow process that can be up to hundreds of years. But in some special conditions,this process can be accelerated because of the break down of the passive state of rebar caused by chloridion, carbon dioxide or other kinds of aggressive matter imported in the concrete.Once the rebar is badly corroded, the maintenance costs of the structure may be severial time higher than the original construction costs. In consequence, the study in the corrosion behaviour of rebar caused by chloridion is of significance.In some special conditons, the contamination of chloridion in concrete is unavoidable,but only the level of chloridion concentration attain a critical value, CTL, the depassivation of the rebar can be caused. Because of the varieties of factors affect the CTL, and the random character of localized corrosion, the CTL reported by different researchers is of great scatter.The conclusion obtained by limited several series of experiments may be casual, therefore the introductuion of statistics method is indispensable. In present work, anodic potentiodynamic polarization curve is used, and pitting potential is selected as the evaluation indicator.Cumulative probability is used to obtain the CTL in three different pH value, 12.5, 12.0 and 11.5, which be used to simulate different degree of neutralization. The result indicate that the CTL in three different pH is 0.1 -0.2mol/L,0.005-0.01 mol/L,and 0.001 mol/L respectively,the CTL value decline about one order of magnitudes with the pH value reduce every 0.5. The corrosion risk of rebar under polarization condition is also evaluated by statistical method.Electrochemical noise and electrochemical impedance spectroscopy technique are used to study the electrochemical feature under open circle potential condition in three different pH value described above, the result shows that the CTL is higher than the conclusion obtained under polarization state. When the Cl-concentration is under this level, the rebar surface is in passive state and keep uniform. While when the Cl- concentration exceed CTL, the breakdown-repassive process will occur in the rebar passive film, and metastable pitting will grow to stability with the sharply rise of corrosion rate. The corrosion state of rebar can be judged by the use of noise resistance and energy distribution plot. Electrochemical noise energy distribution 'A' is propose as the warning index of rebar corrosion.