AASHTO T358-19 pdf free download

AASHTO T358-19 pdf free download.Surface Resistivity 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 resistivity of concrete samples to provide a rapid indication of their resistance to chloride ion penetration. W enner probe measurements have shown good correlations with other electrical indication tests such as the T 277 and the ASTM C1202 tests. In most cases, the electrical resistivity results have shown good correlation with chloride exposure tests, such as ASTM C1556, on companion cylinders cast from the same concrete mixtures (see references in Sections 15.2, 15.4, and 15.5). 4.2. This test method is suitable for evaluation of materials and material proportions for design purposes, as well as for research and development. 4.3. The qualitative terms in the left-hand column of Table 1 should be used in most cases unless . otherwise noted by the specifying agency. The numerical results (resistivity, in kS2-cm) from this test method must be used with caution, especially in applications such as quality control and acceptance testing.4.4. The details of the test method apply to 100-mm (4-in.) and 150-mm (6-in.) nominal diameter specimens. Other specimen diameters may be tested with appropriate changes to the Wenner probe tip spacing and the correction factor in the calculating equation. (See reference in Section 15.3.)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 concrete mixtures including calcium nitrite indicate lower resistivity values, that is, lower resistance to chloride ion penetration, when compared to tests on identical concrete mixtures (controls) without calcium nitrite. However, long- term chloride diffusion tests indicate the concretes with calcium nitrite were at least as resistant to chloride ion penetration as the control mixtures. Note 1- Other admixtures might affect results of this test similarly. Long-term diffusion tests are recommended if an admixture effect is suspected. Sample curing condition is known to affect the resistivity of the solution in the pore structure (see Section 15.4). Lime-water curing on average reduces resistivity by 10 percent. 5.3. Because the test results are a function of the electrical resistance of the specimen, the presence of reinforcing steel or other embedded electrically conductive materials may have a significant effect. The test is not valid for samples containing reinforcing. 5.4. 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. 5.5. The degree of water saturation and concrete temperature may have a significant effect on the electrical resistivity of concrete. A standardized conditioning procedure has been developed to minimize this effect.8. TEST SAMPLES 8.1. A set is composed of a minimum of three samples. Sample preparation and selection depends on the purpose of the test. For evaluation of materials or their proportions, samples may be (a) cores from structures or from larger diameter cast cylinders, (b) 100-mm- (4- in.) diameter cast cylinders, or (c) 150-mm- (6-in.) diameter cast cylinders. Cylinders cast in the laboratory shall be prepared following procedures in R 39. Unless specified otherwise, moist-cure test samples for 28 days prior to testing (Notes 2 and 3).AASHTO T358-19  pdf download.