SCOPEThis Recommendation covers the description of nondestructive electrochemical test methods for the estimation in large size concrete structures of the instantaneous corrosion current density, ioorr, expressed in gA/cm 2, by means of the so-called Polarization Resistance technique, R o, in order to assess the condition of embedded steel reinforcement related to its corrosion.The values of i~orr, Can be used to assess the rate of degradation of concrete structures affected by reinforcement corrosion. However, they cannot give information on the actual loss in steel cross section which, at present, only can be assessed by means of direct visual observation.Values of the free corrosion potential or half-cell potential, Ecorr [V], of the embedded reinforcing steel and of the electrical concrete resistance, Re [f)], are obtained as preliminary steps of the Rp measurements. Values of the concrete resistivity, P [~m], can be calculated from Re values providing the geometrical arrangement of the electrodes enables this calculation.Both parameters, Ecorr and Re (or P) may be used to complement the reliability of the ico~r measurements.
SIGNIFICANCE AND USEThe test methods described in the present Recommendation are suitable for on-site condition assessment of steel reinforced concrete structures.The methods can be applied regardless of the thickness of concrete cover and the rebar size or detailing. However, when the bars are electrically connected, only the corrosion of the closer layer of reinforcements facing the counter electrode, CE, can be measured. This closer reinforcement layer practically shields the penetration of the polarizing current to deeper lying reinforcements. When rebars are electrically isolated, the steel bar connected to the instrument will be measured irrespective of its depth (depths higher than 1 m have been tested).The test methods can be used at any time during the service life of the structure, and in any kind of climate, providing the temperature is higher than 0~ A very dry concrete surface of P > 1000 f~m makes the measurement difficult. Some prewetting of the concrete surface is always necessary.The Icorr results obtained by the test methods can be used for one of the following purposes:1359-5997/04 9 RILEM 623 RILEM TC 154-EMC 1) To assess the present corrosion condition of the reinforcement, that is, to discriminate between corroding and non-corroding (passivated) zones. 2) To evaluate the effectivity of a repair work. 3) To calculate the loss in rebar cross section by means of integration of Ir during the propagation period (providing the initiation time is known). This calculation enables the Lo~r values to be implemented into structural models in order to assess the further development of the structural performance with respect to cover cracking, loss of bond and loss of load-bearing capacity.The corrosion current values in addition to the measurements of the corrosion potential, Er and of the concrete resistivity, P, may be complemented by other data from the concrete: rebar diame...
