AASHTO T 357-2015 Standard Method of Test for Predicting Chloride Penetration of Hydraulic Cement Concrete by the Rapid Migration Procedure.pdf

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1、Standard Method of Test for Predicting Chloride Penetration of Hydraulic Cement Concrete by the Rapid Migration Procedure AASHTO Designation: T 357-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-3c T 357-1 AASH

2、TO Standard Method of Test for Predicting Chloride Penetration of Hydraulic Cement Concrete by the Rapid Migration Procedure AASHTO Designation: T 357-1511. SCOPE 1.1. This procedure is for the rapid evaluation of chloride penetration resistance of concrete, from non-steady-state migration experimen

3、ts. 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 277, Electrical Indication of Concretes Abil

4、ity to Resist Chloride Ion Penetration 2.2. ASTM Standard: D1193, Standard Specification for Reagent Water 3. DEFINITIONS 3.1. Terminology: 3.1.1. chloride penetration depththe distance between the surface exposed to chloride solution and the chloride penetration front where the color changes from w

5、hite to brown after spraying of 0.1N silver nitrate solution. 3.1.2. diffusionthe movement of molecules or ions under a gradient of concentration, or more strictly speaking, chemical potential, from a high concentration zone to a low concentration zone. 3.1.3. migrationthe movement of ions under the

6、 action of an external electrical field. 4. SUMMARY OF TEST METHOD 4.1. This test method uses electrical migration to accelerate the movement of chloride ions into a concrete specimen and a colorimetric indicator to measure the extent of chloride penetration. An external potential is applied axially

7、 across the specimen to force the chloride ions to migrate into the specimen. After a defined test duration, the specimen is axially split and a silver nitrate solution (colorimetric indicator for chloride) is sprayed on one of the fresh split surfaces. The chloride penetration depth is measured fro

8、m the extent of the visible white silver chloride 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 357-2 AASHTO precipitate. From this penetration depth, the rate of chloride ion penetration is de

9、termined and used to rate the concrete. 5. SIGNIFICANCE AND USE 5.1. The results of this test can be used to rate concrete according to the relative ease with which chloride ions can penetrate into the concrete. This in turn gives an indication of the potential for corrosion of reinforcing steel due

10、 to chloride intrusion. 6. APPARATUS 6.1. Water-cooled diamond saw, capable of making cuts perpendicular to the axis of 100-mm diameter concrete cylinders or cores. 6.2. Conditioning Equipment: 6.2.1. Vacuum Desiccator250-mm diameter or larger (capable of containing at least three specimens), allowi

11、ng two hose connections, each of which must be equipped with a stopcock. 6.2.2. Vacuum PumpCapable of maintaining a pressure of less than 5 kPa (37 mm Hg) in the desiccator. Note 1Because the vacuum will be drawn over water, the pump should be protected with a cold trap, or the pump oil should be ch

12、anged after each use. 6.2.3. Vacuum Gauge or ManometerCapable of reading vacuum levels as low as 1 kPa (5 mm Hg). 6.3. Migration apparatus shown schematically in Figure 1 (Note 1). Detailed drawings may be found in Annex A1. Figure 1Schematic of Migration Apparatus 6.3.1. Silicon Rubber SleeveInner/

13、outer diameter 100/115 mm, about 150 mm long. 6.3.2. Two Stainless Steel Clamps20 mm wide with diameter range of 105 to 115 mm. (See Figure 2.) 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 357

14、-3 AASHTO 6.3.3. Plastic Container (Catholyte Reservoir)370 by 270 by 280 mm (L by W by H). 6.3.4. Plastic support with 0.5-mm thick stainless steel plate (cathode) attached. (See Figures A1.1 through A1.5.) 6.3.5. Stainless Steel Mesh or Plate (Anode)With holes, about 0.5 mm thick. (See Figure A1.5

15、.) Note 2Other designs are acceptable provided that temperatures of the specimen and solutions during the test can be maintained in the range of 20 to 25C. Test cells for T 277 have been used successfully in this procedure. Use of T 277 cells requires test specimens to be coated as specified in T 27

16、7 before conditioning. 6.4. Power supply capable of supplying 0- to 60-V direct current (DC)-regulated voltage with the accuracy 0.1 V. 6.5. AmmeterCapable of displaying current to 1 mA. 6.6. Thermometer or ThermocoupleWith readout device capable of reading to 1C. 6.7. Any device suitable for splitt

17、ing the specimen longitudinally, e.g., compression testing machine with split tensile test apparatus. 6.8. Slide CaliperWith 0.1-mm resolution and ruler for measuring. 7. REAGENTS AND MATERIALS 7.1. Purity of ReagentsReagent-grade chemicals shall be used in all tests. Unless otherwise indicated, all

18、 reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such specifications are available. Other grades may be used provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessenin

19、g the accuracy of the determination. 7.2. Purity of WaterUnless otherwise indicated, water shall be reagent-grade water as defined by Type III of ASTM D1193. 7.3. Reagents: 7.3.1. Sodium chloride solution, 10 percent by massdissolve 100 g sodium chloride (NaCl) in 900 g tap water. 7.3.2. Sodium hydr

20、oxide solution, 0.3 Ndissolve approximately 12 g sodium hydroxide in 1 L distilled or deionized water. 7.3.3. Silver nitrate (AgNO2) solution, 0.1 M. 7.4. Sealant: 7.4.1. Five-minute epoxy or other suitable sealant for coating specimen sides, if required by the test apparatus. (See Note 2.) 2016 by

21、the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 357-4 AASHTO 8. SAMPLING, TEST SPECIMENS, AND TEST UNITS 8.1. The method requires cylindrical specimens with a diameter of 100 mm and a thickness of 50 mm,

22、 sliced from cast cylinders or drilled cores with a minimum original length of 100 mm. The cylinders or cores should meet the requirements described in R 39, T 23, or T 24M/T 24. Three specimens should be used in the test. 8.2. Obtaining Test Specimens: 8.2.1. If a drilled core is used, an outer (i.

23、e., closest to the original surface) layer of the concrete (approximately 1020 mm thick) should be cut off (Note 3), after which a 50 2 mm thick slice should be cut from the remaining core length to be used as the test specimen. The end surface of the test specimen that was closest to the original s

24、urface (i.e., the end surface that was adjacent to the discarded outer layer) should be exposed to the chloride solution (catholyte). 8.2.2. If a cast cylinder is used, an outer (i.e., closest to the troweled surface) layer of the concrete approximately 25 mm thick should be cut off (Note 3), after

25、which a 50 2 mm thick slice should be cut from the remaining length of the cylinder to be used as the test specimen. The end surface closest to the original troweled surface should be exposed to the chloride solution (catholyte). 8.2.3. The thickness should be measured to the nearest 0.1 mm with a s

26、lide caliper at four locations equally spaced around the specimen. All four thickness measurements shall be 50 2 mm. Note 3The term “cut” here means to saw perpendicularly to the axis of a core or cylinder by means of a water-cooled diamond saw. 9. CONDITIONING 9.1. Brush and wash away any burrs fro

27、m the surfaces of the specimen. Wipe excess water from the surfaces of the specimens. 9.2. Coat specimen sides with 5-min epoxy or other suitable sealant if required. (See Note 2.) 9.3. Preconditioning (Vacuum Saturation): 9.3.1. Place surface-dry specimens in the vacuum desiccator. Both end surface

28、s must be exposed. 9.3.2. Seal the desiccator and start the vacuum pump. The absolute pressure in the desiccator should decrease to a range of 1 to 5 kPa (7.5 to 37 mm Hg) within a few minutes. Maintain vacuum for 3 h. 9.3.3. With the vacuum pump still running, open the water stopcock and fill the d

29、esiccator with de-aired tap water to cover the specimens. Close the water stopcock and maintain the vacuum for an additional 1 h. 9.3.4. Close the vacuum line stopcock and turn off the vacuum pump. Reopen the vacuum line stopcock to allow air to reenter the desiccator. Maintain the specimens in this

30、 condition for 18 2 h. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 357-5 AASHTO 10. PROCEDURE 10.1. Set Up (Note 4): 10.1.1. Measure the temperature of the NaOH and NaCl solutions. If the tem

31、peratures are not within the range 23 2C, bring the temperatures of the NaOH and NaCl solutions to 23 2C before starting the test. 10.1.2. Place the plastic support (cathode) in the catholyte reservoir and fill the reservoir with about 12 L of NaCl solution. 10.1.3. For each of the three test specim

32、ens, place a rubber sleeve around the specimen as shown in Figure 2 (Note 4). Place clamps as shown in the figure and tighten snugly. Figure 2Assembly of Specimen in Rubber Sleeve and Placement of Anode Note 4If using an apparatus different than the one described here (e.g., T 277 cells), set up the

33、 apparatus in accordance with the applicable standard or the manufacturers instructions. 10.1.4. Fill each sleeve with distilled water to check for leaks, and tighten clamps further if necessary (Note 5). Empty the water and place the specimens on the slanted plastic support (cathode) in the catholy

34、te reservoir (Note 6). Note 5If the curved surface of the specimen is not smooth, or if there are significant defects (e.g., large voids or honeycombs) on the curved surface that may result in significant leakage, apply a strip of silicon sealant to improve the watertightness. Note 6If the concrete

35、has been allowed to dry substantially after preconditioning, immerse it in tap water for a few minutes to resaturate before placing it on the slanted plastic support (cathode) in the catholyte reservoir. 10.1.5. Fill the sleeve above the specimen with 300 ml of NaOH solution. Immerse the anode in th

36、e NaOH solution. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 357-6 AASHTO 10.2. Application of Voltage: 10.2.1. Connect the cathode and anode to the negative and positive poles of the power s

37、upply, respectively. Turn on the power, set the power supply to a potential of 60.0 0.1 V DC, and record the initial current (A) through each specimen to the nearest 0.001 A. 10.2.2. Check the current ranges in Table 1 and, if necessary, reset the potential according to the values in the table. If t

38、he potential is reset, record new values of initial current for each specimen. If the initial current is greater than 800 mA, do not continue with the test. Table 1Test Conditions Initial Current at 60 V (mA) Applied Voltage (V) Test Duration (h) 800 Do not test Do not test 10.2.3. For each specimen

39、, measure and record the initial temperature in the anolyte solution using a thermometer or thermocouple. 10.2.4. After 18 h, record the final current and temperature for each specimen, and record the temperature of the catholyte solution. Turn off the power supply. 10.2.5. Disassemble the test appa

40、ratus and remove test specimens. 10.3. Measurement of Chloride Penetration: 10.3.1. Rinse the specimens with distilled water. Wipe excess water from the surfaces of the specimen. Using a suitable device, split the specimen longitudinally into two pieces. Choose one piece for the penetration depth me

41、asurement. 10.3.2. Spray 0.1 N silver nitrate solution on the fresh-split surface. When the white silver chloride precipitate on the split surface is clearly visible (after about 15 min), use a ruler to measure the penetration depths at intervals of 10 mm, starting 10 mm from the edge, as shown in F

42、igure 3 (Notes 7, 8, and 9). The depth should be read to the nearest millimeter. At least five valid depth measurements should be obtained. Figure 3Measurement of Chloride Penetration Depth on Split Face of Specimen 2016 by the American Association of State Highway and Transportation Officials.All r

43、ights reserved. Duplication is a violation of applicable law.TS-3c T 357-7 AASHTO Note 7If the penetration front to be measured is obviously blocked by the aggregate, move the measurement to the nearest front where there is no significant blocking of aggregate, or alternatively, discard this depth i

44、f there are more than five valid depths. Note 8If the presence of a defect in the specimen (e.g., large void or honeycomb) results in a penetration front much larger than the average, measurement(s) should not be made at this location. Note such defects in the test report. Note 9To eliminate possibl

45、e edge effects due to non-homogeneous degree of saturation or possible leakage during the test, no depth measurement should be made within 10 mm of the edge. (See Figure 3.) 11. CALCULATIONS 11.1. For each test specimen, the depth of penetration is determined by discarding the high and the low value

46、 and taking the mean of the remaining measurements. 11.2. The rate of penetration is calculated by dividing the depth of penetration (mm) by the product of the applied voltage (V) and the test duration (h). 12. REPORT 12.1. Report the following information: 12.1.1. Name and address of the testing la

47、boratory; 12.1.2. Date and identification number of the test report; 12.1.3. Name and address of the organization or person who ordered the test; 12.1.4. Name and address of the manufacturer or supplier of the tested object; 12.1.5. Date of arrival of the tested object; 12.1.6. Description of the te

48、sted object including sampling, composition, and curing age; 12.1.7. Purpose of the test; 12.1.8. Test method; 12.1.9. Any deviation from the test method; 12.1.10. Name and address of the person who performed the test; 12.1.11. Date of the test; 12.1.12. Test information including the specimen dimen

49、sions, applied potential, initial and final currents, and initial and final temperatures; 12.1.13. Average (for three specimens) penetration depth and rate of penetration as well as individual penetration depth measurements for each specimen; 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3c T 357-8 AASHTO 12.1.14. Any unusual observations, such as significant defects in the specimens or a large penetration front due