Analysis of the Rapid Chloride Migration test

In this study the Rapid Chloride Migration test (RCM) standardized as NT Build 492 and BAW-Merkblatt is reviewed. Since the traditional natural diffusion tests are laborious, time consuming and costly, they are not always preferred from a practical point of view. To overcome these disadvantages, several accelerated tests have been developed. Among the accelerated chloride migration tests, the Rapid Chloride Migration test (RCM) seems to be the most promising test to use in the prediction of the chlorides progression into concrete. Nevertheless, because of deficiencies in the theoretical background, the test has received some criticism. The largest issue of the test concerns the assumption of the chloride concentration profile in concrete after the migration test. The S - shaped abrupt chloride penetration front, assumed in the theoretical model, has not been observed in reality. This leads to a wrong estimation of the chloride ion migration coefficient – DRCM. Moreover, the effect of the polarization of electrodes used in the test and the differences in the quality of concrete from the inner layers (the tested part of concrete in the RCM test) and outer layers (the concrete which is the real barrier against the chlorides test) have not been studied sufficiently and are considered having a significant effect on the RCM test results. The investigations presented in this paper include results of the measurements of the polarization of electrodes, the influence of curing of concrete on the quality of concrete cover, the differences in quality between concrete in the inner and outer layers and the discussion of the consequences of assuming an incorrect chloride penetration front in the RCM model. Considering the investigations, some modifications of the RCM test procedure are proposed and a further direction of research is outlined