Standard Test Method for Electrical Indication of Concrete’s Ability to Resist Chloride Ion Penetration

Abstract

4.1 This test method covers the laboratory evaluation of the electrical conductance of concrete samples to provide a rapid indication of their resistance to chloride ion penetration. In most cases the electrical conductance results have shown good correlation with chloride ponding tests, such as AASHTO T259, on companion slabs cast from the same concrete mixtures (Refs 1-5). 4.2 This test method is suitable for evaluation of materials and material proportions for design purposes and research and development. 4.3 Sample age has significant effects on the test results, depending on the type of concrete and the curing procedure. Most concretes, if properly cured, become progressively and significantly less permeable with time. 4.4 This test method was developed originally for evaluations of alternative materials, but in practice its use has evolved to applications such as quality control and acceptance testing. Factors such as ingredient materials used in concrete mixtures and the method and duration of curing test specimens affect the results of this test (see Note 1). When this method is used for mixture qualification and acceptance testing, it is imperative that the curing procedures and the age at time of testing be clearly specified. Note 1: When using this test for determining acceptability of concrete mixtures, statistically-based criteria and test age for prequalification, or for acceptance based on jobsite samples, should be stated in project specifications. Acceptance criteria for this test should consider the sources of variability affecting the results and ensure balanced risk between supplier and purchaser. The anticipated exposure conditions and time before a structure will be put into service should be considered. One approach to establishing criteria is discussed in Ref (6). 4.5 Table X1.1 in Appendix X1 provides a qualitative relationship between the results of this test and the chloride ion penetrability of concrete. 4.6 Care should be taken in interpreting results of this test when it is used on surface-treated concretes, for example, concretes treated with penetrating sealers. The results from this test on some such concretes indicate low resistance to chloride ion penetration, while 90 day chloride ponding tests on companion slabs show a higher resistance. 4.7 The details of the test method apply to 100 mm nominal diameter specimens. This includes specimens with actual diameters ranging from 95 mm to 100 mm. Other specimen diameters may be tested with appropriate changes in the applied voltage cell design (see 7.5 and Fig. 1). 4.7.1 For specimen diameters other than 95 mm, the test result value for total charge passed must be adjusted following the procedure in 11.2. For specimens with diameters less than 95 mm, particular care must be taken in coating and mounting the specimens to ensure that the conductive solutions are able to contact the entire end areas during the test.