AASHTO T 277-2015 Standard Method of Test for Electrical Indication of Concrete s Ability to Resist Chloride Ion Penetration.pdf

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1、Standard Method of Test for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration AASHTO Designation: T 277-15 ASTM Designation: C1202-12 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c T

2、 277-1 AASHTO Standard Method of Test for Electrical Indication of Concretes Ability to Resist Chloride Ion Penetration AASHTO Designation: T 277-15 ASTM Designation: C1202-12 1. SCOPE 1.1. This test method covers the determination of the electrical conductance of concrete to provide a rapid indicat

3、ion of its resistance to the penetration of chloride ions. This test method is applicable to types of concrete where correlations have been established between this test procedure and long-term chloride ponding procedures such as those described in T 259. Examples of such correlations are discussed

4、in References 15.1 through 15.5.11.2. The values stated in SI units are to be regarded as the standard. 1.3. The text of this standard references notes and endnotes which provide explanatory materials. These notes and endnotes (excluding those in tables and figures) shall not be considered as requir

5、ements of the standard. 1.4. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations pri

6、or to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 39, Making and Curing Concrete Test Specimens in the Laboratory T 23, Making and Curing Concrete Test Specimens in the Field T 24M/T 24, Obtaining and Testing Drilled Cores and Sawed Beams of Concrete T 259, Resistance of Concrete to Chlori

7、de Ion Penetration 2.2. ASTM Standard: C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 3. SUMMARY OF TEST METHOD 3.1. This test method consists of monitoring the amount of electrical current passing through 50-mm (2-in.) thick slices of

8、 100-mm (4-in.) nominal diameter cores or cylinders during a 6-h period. A potential difference of 60 V dc is maintained across the ends of the specimen, one of which is immersed in a sodium chloride solution and the other in a sodium hydroxide solution. The total charge passed, in coulombs, has bee

9、n found to be related to the resistance of the specimen to chloride ion penetration. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 277-2 AASHTO 4. SIGNIFICANCE AND USE 4.1. This test method cov

10、ers 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

11、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

12、 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 accep

13、tance 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

14、the age at time of testing be clearly specified. Note 1When 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 fo

15、r 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 Re

16、ference 15.6. 4.5. Table 1 in 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

17、 control and acceptance testing. The qualitative terms in the right-hand column of Table 1 should be used in most cases unless otherwise noted by the specifying agency. Table 1Chloride Ion Penetrability Based on Charge Passed Charge Passed, C Chloride Ion Penetrability 4000 High 20004000 Moderate 10

18、002000 Low 1001000 Very low 100 Negligible 4.7. 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 p

19、enetration, while 90-day chloride ponding tests on companion slabs show a higher resistance. 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.). 2016 by the American Ass

20、ociation of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 277-3 AASHTO 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 diamet

21、ers 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 solution

22、s 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. 2016 by the Am

23、erican Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 277-4 AASHTO Equivalents Item Qty. Nomenclature Specification 1.A 1.B 1 1 Cell block end DMMA sheet 2 4 Shim, brass 0.5 mm (0.02 in.) THK 3 2 Screen, brass 0.85

24、mm (No. 20) mesh. “A” diameter 4 2 Wire, copper 14, solid Nyclad 5 2 Terminal 12-10-1/46 2 Banana plug 6.4 mm (0.25 in.) male insulated Figure 1Applied Voltage Cell (Construction Drawing) 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication

25、is a violation of applicable law.TS-3c T 277-5 AASHTO 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 i

26、on 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. Note 2Other admixtures might affect

27、 results of this test similarly. Long-term ponding tests are recommended if an admixture effect is suspected. 5.2. 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 si

28、gnificant effect. The test is not valid for specimens containing reinforcing steel positioned longitudinally; that is, providing a continuous electrical path between the two ends of the specimen. 6. APPARATUS 6.1. Vacuum Saturation Apparatus: (See Figure 2, for example.) Figure 2Vacuum Saturation Ap

29、paratus 6.1.1. Separatory FunnelOr other sealable, bottom-draining container with a minimum capacity of 500 mL. 6.1.2. Beaker(1000 mL or larger) or other container. Capable of holding concrete specimen(s) and water and of fitting into the vacuum desiccator. (See Section 6.1.3.) 6.1.3. Vacuum Desicca

30、tor250-mm (9.8-in.) inside diameter or larger. The desiccator must allow two hose connections, through a rubber stopper and sleeve or through a rubber stopper only. Each connection must be equipped with a stopcock. 6.1.4. Vacuum PumpCapable of maintaining a pressure of less than 6650 Pa (50 mmHg) in

31、 a desiccator. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 277-6 AASHTO Note 3Because the vacuum will be drawn over water, the pump should be protected with a water trap or pump oil should be

32、 changed after each operation. 6.1.5. Vacuum Gauge or ManometerAccurate to 665 Pa (5 mmHg) over range 0 to 13 300 Pa (0 to 100 mmHg) pressure. 6.2. Coating Apparatus and Materials: 6.2.1. CoatingRapid setting, electrically nonconductive, capable of sealing side surface of concrete cores. 6.2.2. Bala

33、nce or Scale, Paper Cups, Wooden Spatulas, and Disposable BrushesFor mixing and applying coating. 6.3. Specimen-Sizing EquipmentNot required if samples are cast to final specimen size. 6.3.1. Movable Bed Water-Cooled Diamond Saw or Silicon Carbide Saw. 7. REAGENTS, MATERIALS, AND TEST CELL 7.1. Spec

34、imen-Cell SealantCapable of sealing concrete to polymethylmethacrylate, for example, Plexiglas, against water and dilute sodium hydroxide and sodium chloride solutions at temperatures up to 90C (200F); examples include RTV silicone rubbers, silicone rubber caulkings, other synthetic rubber sealants,

35、 silicone greases, and rubber gaskets. 7.2. Sodium Chloride Solution3.0 percent by mass (reagent grade) in distilled water. 7.3. Sodium Hydroxide Solution0.3 Normal (reagent grade) in distilled water. 7.3.1. WarningBefore using NaOH, review: (1) the safety precautions for using NaOH; (2) first aid f

36、or burns; and (3) the emergency response to spills, as described in the manufacturers Material Safety Data Sheet or other reliable safety literature. NaOH can cause very severe burns and injury to unprotected skin and eyes. Suitable personal protective equipment should always be used. These should i

37、nclude full-face shields, rubber aprons, and gloves impervious to NaOH. Gloves should be checked periodically for pin holes. 7.4. Filter Papers90-mm (No. 2) diameter (not required if rubber gasket is used for sealant (Section 7.1) or if sealant can be applied without overflowing from shim onto mesh)

38、. 7.5. Applied Voltage Cell (Figures 1 and 3)Two symmetric polymethylmethacrylate chambers, each containing electrically conductive mesh and external connectors. One design in common use is shown in Figures 1 and 3. However, other designs are acceptable, provided that overall dimensions (including d

39、imensions of the fluid reservoir) are the same as shown in Figure 1 and width of the screen and shims are as shown. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 277-7 AASHTO Figure 3Applied Vo

40、ltage Cell-Face View 7.6. Temperature-Measuring Device (optional)0 to 120C (30 to 250F) range. 7.7. Voltage Application and Data Readout ApparatusCapable of holding 60 0.1 V dc across applied voltage cell over entire range of currents and of displaying voltage accurate to 0.1 V and current to 1 mA.

41、Apparatus listed in Sections 7.7.1 through 7.7.5 is a possible system meeting this requirement. 7.7.1. VoltmeterDigital (DVM), 3-digit, minimum 099.9 V range, rated accuracy 0.1 percent. 7.7.2. VoltmeterDigital (DVM), 41/2-digit, 0200 mV range, rated accuracy 0.1 percent. 7.7.3. Shunt Resistor100 mV

42、, 10A rating, tolerance 0.1 percent. Alternatively, a 0.01- resistor, tolerance 0.1 percent, may be used, but care must be taken to establish very low resistance connections. 7.7.4. Constant Voltage Power Supply080 V dc, 02 A, capable of holding voltage constant at 60 0.1 V over entire range of curr

43、ents. 7.7.5. CableTwo conductor, 1.6 mm (No. 14), insulated, 600 V. 8. TEST SPECIMENS 8.1. Sample preparation and selection depends on the purpose of the test. For evaluation of materials or their proportions, samples may be (a) cores from test slabs or from large diameter cylinders or (b) 100-mm (4

44、-in.) diameter cast cylinders. For evaluation of structures, samples may be (a) cores from the structure or (b) 100-mm (4-in.) diameter cylinders cast and cured at the field site. Coring shall be done with a drilling rig equipped with a 100-mm (4-in.) diameter diamond-dressed core bit. Select and co

45、re samples following procedures in T 24M/T 24. Cylinders cast in the laboratory shall be prepared following procedures in R 39. Unless specified otherwise, moist cure test specimens for 56 days prior to the start of specimen preparation (Note 4). When cylinders are cast in the field to evaluate a st

46、ructure, care must be taken that the cylinders receive the same treatment as the structure, for example, similar degree of consolidation, curing, and temperature history during curing. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is

47、a violation of applicable law.TS-3c T 277-8 AASHTO Note 4This test method has been used with various test durations and curing regimens to meet agency guidelines or specifications. Care should be exercised when comparing results obtained from specimens subjected to differing conditions. Note 5The ma

48、ximum allowable aggregate size has not been established for this test. Users have indicated that test repeatability is satisfactory on specimens from the same concrete batch for aggregates up to 25.0-mm (1-in.) nominal maximum size. 8.2. When results of this test method are used for evaluation of ma

49、terials or mixture proportions based on cast specimens for purposes of quality control, mixtures submittals, or acceptance of concrete, prepare at least two 100-mm diameter cylindrical specimens in accordance with R 39 for concrete mixtures prepared in the laboratory or T 23 from samples of fresh concrete obtained in the field. Moist cure specimen in accordance with 8.2.1 for concrete mixtures containing only portland cement. For concrete mixtures containing only supplementary cementitious materials use extended m