AASHTO T 277-15 pdf free download
AASHTO T 277-15 pdf free download.Electrical Indication of Concrete’s Ability to Resist Chloride lon Penetration.
4. SIGNIFICANCE AND USE
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 T 259, on companion slabs cast from the same concrete mixtures (References 15.1 through 15.5).
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 evaluation 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 I —When using this test for determining acceptability of concrete mixtures, statistically based criteria and test age for prequalifi cation 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 result 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 Reference 15.6.
4.5. Table 1 provides a qualitative relationship between the results of this test and the chloride ion penetrability of concrete.
4.6. The numerical results (total charge passed, in coulombs) from this test method must be used with caution, especially in applications such as quality control and acceptance testing. The qualitative terms in the right-hand column of Table I should be used in most cases unless otherwise noted by the specifying agency.
4.8. The details of the test method apply to 100-mm (4-in.) nominal diameter specimens. This includes specimens with actual diameters ranging from 95 mm (3.75 in.) to 100 mm (4 in.). Other specimen diameters may be tested with appropriate changes in the applied voltage cell design. (See Section 7.5 and Figure 1.)
4.8.1. For specimen diameters other than 95 mm (3.75 in.), the test result value for total charge passed must be adjusted following the procedure in Section 11.2. For specimens with diameters less than 95 mm (3.75 in.), 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.
4.9. Sample age may have 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.
5. INTERFERENCES
5.1. This test method can produce misleading results when calcium nitrite has been admixed into a concrete. The results from this test on some such concretes indicate higher coulomb values, that is, lower resistance to chloride ion penetration, than from tests on identical concrete mixtures (controls) without calcium nitrite. However, long-term chloride ponding tests indicate the concretes with calcium nitrite were at least as resistant to chloride ion penetration as the control mixtures.AASHTO T 277-15 pdf download.
