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采用交流阻抗谱检测腐蚀电流密度并判断钢筋腐蚀开始的时间,腐蚀开始后通过化学滴定法获得自由氯离子质量分数和总氯离子质量分数,研究了粉煤灰和矿渣对砂浆中引起钢筋锈蚀的临界氯离子浓度的影响规律,探讨了钢筋腐蚀过程的电化学阻抗谱变化以及粉煤灰和矿渣对氯离子结合能力的影响。结果表明:在固定水胶比和胶凝材料用量的情况下,临界氯离子质量分数随矿物掺合料掺量的增加而降低;当粉煤灰掺量达到30%(质量分数,下同)或矿渣掺量达到50%时,临界自由氯离子质量分数由0.52%分别降低到0.33%和0.21%,临界总氯离子质量分数由0.77%分别降低到0.56%和0.38%。钢筋在腐蚀过程中阻抗谱的低频区弧线半径逐渐减小,而高频区基本没变化;掺入粉煤灰和矿渣后,基体对氯离子的结合能力增强。
The corrosion current density was measured by AC impedance spectroscopy to determine the time of corrosion initiation. The free chlorine ion mass fraction and total chloride ion mass fraction were obtained by chemical titration after the start of corrosion. The effects of fly ash and slag on the corrosion of reinforcing steel bars in mortar The influence of chloride concentration on the chloride ion concentration was discussed. The electrochemical impedance spectroscopy (EIS) of corrosion process and the influence of fly ash and slag on the chloride ion binding capacity were discussed. The results show that the critical chloride ion concentration decreases with the increase of the content of mineral admixture when the ratio of water to binder and the amount of cementitious material are fixed. When the content of fly ash reaches 30% (mass fraction) Or the content of slag reaches 50%, the critical free chlorine content decreases from 0.52% to 0.33% and 0.21% respectively, and the critical mass fraction of total chloride decreases from 0.77% to 0.56% and 0.38% respectively. In the process of corrosion, the arc radius of the low-frequency region of the impedance spectrum gradually decreases while the high-frequency region does not change basically. The incorporation of fly ash and slag increases the binding capacity of the substrate to chloride ions.