Evaluation of chloride diffusion coefficient in concrete by the rapid chloride penetration tests: problems and observations.

The so-called rapid chloride permeability test (ASTM C1202) has often been used to assess the resistance of the concrete to penetration of chloride ions, by measuring the amount of electric current passed through the specimen. However, although it has been recognised that there is little correlation between the amount of current passed and the depth of chloride penetration, the test is still used based on the above premise. The results of chloride penetration in this test are also used to derive chloride diffusion coefficients, based on the theories of diffusion. This study confirms that the current and temperature rise during the test period are not greatly dependent on the chloride penetration, which is very limited in the actual test. Therefore, the electrical resistance of concrete indicated by the test, in a shorter time than the prescribed test duration (6 hours), can be used for categorising the penetrability of concrete to chloride ions. This paper describes a number of phenomena we observed in using the test, which indicate that the mechanisms implied by the theories did not eventuate. This caused the results to deviate from the predictions of the diffusion theories. Improvements are suggested for the test. (a) For the covering entry of this conference, please see ITRD abstract no. E217099.