基于护环技术的混凝土中钢筋腐蚀监测研究

采用护环电极(Guard Ring Electrode,GRE,GE)测量方法,探讨辅助电极(CE)、护环电极(GE)在钢筋极化过程中的电流分配比,以及护环电极补偿电流的大小对正确测量研究区域内的钢筋极化电阻Rp的影响.结果表明,为获得较准确的极化电阻Rp值,即要将极化电流补偿在辅助电极CE的投影面积上,仅仅考虑到二维表面的电流(电位差)补偿是不够的.对于高阻混凝土(钝态钢筋)体系,简单的表面电流补偿导致测量的Rp值偏小,只有考虑到混凝土结构中三维空间的电流补偿,才可能得到准确的Rp值.同时将测量结果与均匀极化测量结果进行了对比.结果表明,对于活化态的钢筋混凝土体系,采用护环电极能够较好地将极化电流补偿在工作区域内,从而可对钢筋混凝土体系进行准确的腐蚀测量.

FIELD CORROSION MONITORING OF REBARS IN CONCRETE BY GUARD RING ELECTRODE METHOD

When the general three-electrode system was used to detect corrosion rate of on-site large reinforced concrete,it was prone to result in non-uniform current distribution on the surface of rebars because of the large diffenence in size between counter electrode(CE) and work electrode(rebars).Therefore,polarization surface area of rebars was difficult to be decided.To solve the problem,guard ring electrode method(GEM) was applied.The current ratio of CE and guard-ring electrode(GE) had been studied during polarization of rebars.Furthermore,the effect of GE current was also studied for the sake of obtaining accurate polarization resistance R_p value in the different corrosive states of rebars.In order to achieve real R_p value,CE current must be compensated in the projection rebar area below CE.During the experiment,the potential difference of concrete surface between RE2 and RE3 was monitored at all times.However,it is insufficient to consider only two-dimension current distribution.Generally very high concrete resistance tends to result in small measuring R_p value because of the insufficient compensation of CE current.In order to obtain real R_p value,three-dimension other than two-dimension current distribution must be considered.Compared with uniform polarization results,it was found that CE polarization current could be compensated preferably in the projection area of rebars below CE by GEM when rebars were active,indicating that GEM can be used to monitor the corrosion behavior of rebars in concrete more accurately than other traditional linear polarization resistance method.