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    基于护环电极（GRE）原理，研究了提高钢筋混凝土在线腐蚀速率测量精度的方法;通过GRE电极将极化电流约束在辅助电极CE投影面区域内的钢筋网架内确定钢筋的被极化面积;同时，采用智能GRE电流约束值修正程序，使钢筋腐蚀速率测量值与均匀极化技术测量值保持一致性.结果表明，GRE约束系数λ与混凝土自生电阻率及钢筋腐蚀状态有一定的函数关系，当GRE电流对CE极化电流进行完全约束时即λ=1，钝化态钢筋腐蚀速率将比实际值偏小几倍.要准确测量钢筋锈蚀速率，钢筋自腐蚀电位E_corr越负，混凝土电阻R_c越小，则约束系数λ也必须减小，基于此文中提出了一种基于E_corr和Rc的智能约束系数计算程序，并研制了便携式在线钢筋锈蚀检测仪.现场试验证明：对于活化态钢筋，λ=0.2～0.6，而对于钝化态钢筋，λ=0.5～0.8时腐蚀速率测量结果较为准确.

    Based on the principle of the guard ring electrode (GRE) ,a guard ring is applied to confine the spread of CE polarization current within a constant area.The quasi-proportional relationship between the confinement efficiency λand the electrical resistivity(ρc) of the concrete and the half-cell potential EHC of the concrete has been found after comparing the results measured by Guard Ring Method(GRM)and Uniform Polarization Method(UPM).Full confinement(λ=1)for the CE polarization current will lead to a underestimation of concrete corrosion rates in passive state.Meanwhile,in order to obtain the accurate corrosion rate,aλvalue varied with the self corrosion potential Ecorr of the rebar and the concrete resistance Rc by the help of smart arithmetic is more suitable than a constant value generally applied in some commercial corrosion meter.We found that theλvalue should decrease as Rc decreases and Ecorr going negative.In fact,GRM can give accurate corrosion rate in active rebar state w only when the λ ranged in 0.2～0.6,and in passive state only when the λ within the range 0.5～0.8.