氯盐环境下复合胶凝材料砂浆中钢筋锈蚀状态

Corrosion State of Reinforcing Steel in Composite Binder Mortar in Chloride Environment

采用腐蚀电位、线性极化、循环动电位极化等电化学方法,研究了氯盐环境下偏高岭土(MK)改性复合胶凝材料砂浆中钢筋的锈蚀状态,分析了不同电化学参数之间的关系。结果表明:在氯盐环境中,当MK掺量不高于MK/水泥总质量的30%时,随MK掺量的增加,复合胶凝材料中钢筋的腐蚀电位增大,锈蚀速率降低,耐点蚀性能增强;复合胶凝材料砂浆中钢筋的腐蚀电流密度与腐蚀电位存在相关关系;循环动电位极化测试的电化学参数可以反映复合胶凝材料砂浆内部钢筋的点蚀破坏程度;MK改善了复合胶凝材料砂浆的孔隙结构,降低了复合胶凝材料砂浆的氯离子扩散系数。复合胶凝材料砂浆延长了钢筋的脱钝化时间和钢筋保护层的预期开裂时间。

The corrosion state of composite binder mortar with metakaolin(MK) in chloride environment was investigated by measuring corrosion potential, linear polarization and cyclic potentiodynamic polarization. The relationships among different electrochemical parameters were analyzed. In chloride environment, the corrosion potential of the reinforcing steel in the composite binder mortar increases, the corrosion rate decreases and the pitting corrosion resistance enhances with increasing the MK content as the MK content is < 30%(accounting for total mass of MK and cement). The corrosion current density and corrosion potential are correlated to composite binder mortar. The degree of pitting corrosion of the reinforcing steel in the composite binder mortar is well reflected by main electrochemical parameters of cyclic potentiodynamic polarization. The presence of MK modifies the pore structure and reduces the permeability coefficient of the chloride in the composite binder mortar. The depassivation time of the reinforcing steel and the expected cracking time of reinforcing steel cover both are prolonged when the composite binder mortar is added.