Electrochemical Test And In Situ Corrosion Monitoring Of Chloride Contaminated Reinforced Concrete

The reinforced concrete structures (RCS) have been the widespread materials in the modern architecture. But damage caused by the surroundings also has taken palce. It is thought to be that corrosion of the reinforcement is the main cause of the damage to concrete structures. Besides, corrosion of steel bars not only leads to tremendous economic loss, but also has a terrible effect on the energy and environment. Then it gives rise to structure failure and durability problems of the RCS structure, finally the engineering service life is far less than design requirements. Therefore, it is of crucial importance to monitor the reinforcement corrosion anyway.Corrosion of the reinforcement in RCS is an electrochemical process, so electrochemical measurement is thought to be the best method compared with the analysis and physical methods. The technique is rapid, high sensitive and non-intrusive. Therefore attention is paid exclusively on electrochemical measurements which will promote its development.So far, Linear Polarisation Resistance(LRP) measurements have become a well established method of determining an instantaneous corrosion rate measurement of reinforcing steel in concrete. In situ measurements of steel corrosion rate in large reinforced concrete structures face two kinds of difficluties associated with LRP measurements(i) IR drop of polarization current through concrete ,and (ii)the uncertainty of perturbed rebar area.In this paper, discussions on the methods to eliminate the errors of LRP measurements. Methods are the adoption of reference electrodes inserted in the concrete which are prepared suitable for RCS and the improvement of counter electrode. Based on tri-electrode system,there are a number of comparisations about effect on rhe rebars corrosion rate through variable electrochmical pameters,including cover depth , the chloride ion content and so on.Contrast the electrical resistance between the concrete and the mortar below the sieve in order to establish the impact factors of coarse aggregate. Dot matrix electrode is invented in that it is suitable for in situ montoring the steel corrosion rate and compared with guard ring electrode and auxiliary electrode palte because of its stable test data and good correlation to the losing weight method.By the change of cover depth and the chloride ion content,relationship has been established between linear polarization measurment and the weight loss method under dot matrix electrode.in other words relationship between non-intrusive in situ technique and actual corrosion rate of rebars.In reality, to calculate the Rp per unit of surface area it is necessary to know the rebar area over which the applied current is distributed, which is not easy in"in situ"measurements that use a counter-electrode(CE) of a much smaller size than the reinforced concrete structure which constitutes (WE) the working electrode.The simplification of supposing this area to be equal to that of the CE is risky,since in principle there is no guarantee that all the current flowing from the CE is concentrated in the region of the WE directly below the CE. Many literatures show that more and more researchers are committed to using guard ring electrodes to enhance the accuracy of linear polarization corrosion rate measurements on RCS. The circumstance difference between the laboratory and the construction site brings about many problems about the LRP measurements. So in the paper ,simulating construction site testing is inevitable and novel. By in situ transient test on the concrete plate,correlation of in situ test and the weight losing method have been got.which will open a new area in monitoring the corrosion rate of steel rebars.