Study On Intelligent Compensation Technology Of Guard Ring Method In Concrete Rebar Corrosion Monitoring Instrument

At the present time,the monitoring of concrete lifespan is a very important research field,as a result,reinforcement corrosion monitoring become a very significant engineering problem. However,the common three-electrode system is prone to cause non-uniform current distribution on the surface of rebars because of the small-scale Counter Electrode (CE),and the electric signal of CE gradually decays or vanishes with its distance from CE. As a result,the polarization area of the rebars can not be confirmed in a certain location.Using Guard Ring Method (GRM)which based on the general three-electrode system with addition of a Guard Ring Electrode (GE) to surrounding CE,to settle indeterminate polarization area problem. The potential D-valueΔφof RE₂ and RE₃ in internal concrete has been compensated by GE. Complete compensation experiments showed that the GRM can not give accurate quantitative information and the measured results always less than the real corrosion rate of the rebar. In the actual polarization process,the power line distribution appears non-uniformed . Therefore,assuming same polarization area and same compensation degree for different corroding surrounding is unreasonable. In order to acquire real corrosion rate,a compensation coefficientλvalue has been invented in this paper,a series of experiments on the application of the different compensation degree to potential D-valueΔφof RE₂ and RE₃ in different depth inside concrete for active and passive corrosion system have been accomplished.Concretely speaking,the following works have been completed in this thesis:At first,detailed researches have been done to study the relationship between external environment and the corrosion rate. External environment has heavy effect on the corrosion state of reinforced concrete. From summer to winter,the concrete resistance Rc increases approximately 4 times for both the active and the passive concrete system,the concrete/steel interface polarization resistance R_p rise 4⁶ times for active state whiles less than 1 times for passive state,the corrosion rate i_corr of active system changes most,about 5 times,but the i_corr of passive state almost holds constant.And then,A series of GRM experiments with different compensation coefficientλhave been accomplished .In active state,the bigger the polarization potential span,the bigger the neededλvalue,the determination ofλis also related to the corrosion rate i_corr of steel and concrete resistance,the bigger the rebar's i_corr,the smaller the neededλvalue. Meanwhile,the bigger the concrete Rc,the bigger the neededλvalue. However,the passive system has a homogeneous corrosion state,external environment has little effect on the steel's i_corr and the neededλis independent of concrete resistance Rc,whether in two-dimension or in three-dimension,the neededλranged from 0.6⁰.8 for GRM precise measurement.At last,based on previous theoretical and experimental analyses,the Intelligent Portable Instrument for corrosion monitoring by Guard Ring Technique has been exploited and the accuracy rise about 3 times comparing with like products in abroad.