1、Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Asphalt Mixtures AASHTO Designation: T 324-17 Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 2
2、49 Washington, D.C. 20001 TS-2c T 324-1 AASHTO Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Asphalt Mixtures AASHTO Designation: T 324-17 Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August 2017) 1. SCOPE 1.1. This test method describes a procedure for t
3、esting the rutting and moisture-susceptibility of asphalt mixture pavement samples in the Hamburg Wheel-Tracking Device. 1.2. The method describes the testing of submerged, compacted asphalt mixture in a reciprocating rolling-wheel device. This test provides information about the rate of permanent d
4、eformation from a moving, concentrated load. A laboratory compactor has been designed to prepare slab specimens. Also, the Superpave Gyratory Compactor (SGC) has been designed to compact specimens in the laboratory. Alternatively, field cores having a diameter of 150 mm (6 in.), 250 mm (10 in.), or
5、300 mm (12 in.), or saw-cut slab specimens may be tested. 1.3. The test method is used to determine the premature failure susceptibility of asphalt mixture due to weakness in the aggregate structure, inadequate binder stiffness, or moisture damage. This test method measures the rut depth and number
6、of passes to failure. 1.4. This test method measures the potential for moisture damage effects because the specimens are submerged in temperature-controlled water during loading. 1.5. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address
7、all of the safety concerns 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 prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 30, Mixture Conditio
8、ning of Hot Mix Asphalt (HMA) T 166, Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Saturated Surface-Dry Specimens T 168, Sampling Bituminous Paving Mixtures T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA) T 269, Percent Air Voids in Compacted
9、 Dense and Open Asphalt Mixtures T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS
10、-2c T 324-2 AASHTO 2.2. ASTM Standard: D6027, Standard Test Method for Calibrating Linear Displacement Transducers for Geotechnical Purposes (withdrawn 2013) 3. SIGNIFICANCE AND USE 3.1. This test measures the rutting and moisture susceptibility of an asphalt mixture specimen. 4. SUMMARY OF METHOD 4
11、.1. A laboratory-compacted specimen of asphalt mixture, a saw-cut slab specimen, or a core taken from a compacted pavement is repetitively loaded using a reciprocating steel wheel. The specimen is submerged in a temperature-controlled water bath at a temperature specified by the agency. The deformat
12、ion of the specimen, caused by the wheel loading, is measured. 4.2. The impression is plotted as a function of the number of wheel passes. An abrupt increase in the rate of deformation may coincide with stripping of the asphalt binder from the aggregate in the asphalt mixture specimen. 5. APPARATUS
13、5.1. Hamburg Wheel-Tracking DeviceAn electrically powered machine capable of moving a 203.2 2.0-mm (8 0.08-in.) diameter, 47-mm (1.85-in.) wide steel wheel over the center (x and y axes) of the test specimen. The load on the wheel is 705 4.5 N (158 1.0 lb). The wheel reciprocates over the specimen,
14、with the position varying sinusoidally over time. The wheel makes 52 2 passes across the specimen per minute. The maximum speed of the wheel, reached at the midpoint of the specimen, is approximately 0.305 m/s (1 ft/s). 5.2. Temperature Control SystemA water bath capable of controlling the temperatu
15、re within 1.0C (1.8F) over a range of 25 to 70C (77 to 158F) with a mechanical circulating system stabilizing the temperature within the specimen tank. 5.3. Impression Measurement SystemA linear variable differential transducer (LVDT) device capable of measuring the depth of the impression (rut) of
16、the wheel at the center 1/2in. along the length of the wheels path, to within 0.15 mm (0.006 in.), over a minimum range of 0 to 20 mm (0 to 0.8 in.). The system measures the rut depth, without stopping the wheel, at least every 400 passes. Rut depth is expressed as a function of the wheel passes. No
17、te 1Users may require the capability of impression measurements at different intervals across the length of the wheels path on the test specimen. 5.4. Wheel Pass CounterA non-contacting solenoid that counts each wheel pass over the specimen. The signal from this counter is coupled to the wheel impre
18、ssion measurement, allowing for the rut depth to be expressed as a function of the wheel passes. 5.5. Slab Specimen Mounting SystemA stainless steel tray that is mounted rigidly to the machine. The mounting system must restrict shifting of the specimen to within 0.5 mm (0.02 in.) during testing and
19、must suspend the specimen to provide a minimum of 20 mm (0.8 in.) of free circulating water on all sides. 5.6. Cylindrical Specimen Mounting SystemAn assembly consisting of two high-density polyethylene (HDPE) molds or plaster of paris, conforming to Section 8 to secure the specimen (as shown in Fig
20、ures 1 and 2), placed in a stainless steel tray that is mounted rigidly to the 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 324-3 AASHTO machine. This mounting system must restrict shifting o
21、f the specimen to within 0.5 mm (0.02 in.) during testing and must suspend the specimen to provide a minimum of 20 mm (0.8 in.) of free circulating water on all sides. Figure 1Cylindrical Specimen Mounting System Figure 2Schematic of Cylindrical Specimen Mounting System 2017 by the American Associat
22、ion of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 324-4 AASHTO 5.7. Linear Kneading CompactorA hydraulic-powered unit that uses a series of vertically aligned steel plates to compact molded asphalt mixtures into flat, rectang
23、ular slabs of predetermined thickness and density. 5.8. BalanceOf 12 000-g capacity, accurate to 0.1 g. 5.9. OvensFor heating aggregate and asphalt binders. 5.10. Superpave Gyratory Compactor (SGC)And molds conforming to T 312. 5.11. Bowls, spoon, spatula, etc. 6. SPECIMEN PREPARATION 6.1. Number of
24、 Test SpecimensPrepare two test specimens for each test, either slab specimens or cylinders. 6.2. Laboratory-Produced Asphalt Mixture: 6.2.1. Batch mixture proportions in accordance with the desired job mix formula. 6.2.2. Use the mixing temperature at which the asphalt binder achieves a viscosity o
25、f 170 20 cSt. For modified asphalt binders, use the mixing temperature recommended by the binder manufacturer. 6.2.3. Dry-mix the aggregates and mineral admixture (if used) first, then add the correct percentage of asphalt binder. Mix the materials to coat all aggregates thoroughly. (Wet-mix the agg
26、regates if using a lime slurry or other wet material.) 6.2.4. Condition test samples at the appropriate compaction temperature in accordance with the short-term conditioning procedure for mechanical properties in R 30. 6.2.5. Use the compaction temperature at which the asphalt binder achieves a visc
27、osity of 280 30 cSt. For modified asphalt binders, use the compaction temperature recommended by the binder manufacturer. 6.2.6. Laboratory Compaction of SpecimensCompact either slab specimens or SGC cylindrical specimens. 6.2.6.1. Compacting Slab SpecimensHeat molds and tools to compaction temperat
28、ure. Compact slab specimens 320 mm (12.5 in.) long and 260 mm (10.25 in.) wide using a Linear Kneading Compactor (or equivalent). Specimen thickness must be at least twice the nominal maximum aggregate size, generally yielding a specimen 38 to 100 mm (1.5 to 4 in.) thick. Allow compacted slab specim
29、ens to cool at normal room temperature on a clean, flat surface until cool to the touch. 6.2.6.2. Compacting SGC Cylindrical SpecimensCompact two 150-mm (6-in.) diameter specimens in accordance with T 312. Specimen thickness must be at least twice the nominal maximum aggregate size, generally yieldi
30、ng a specimen 38 to 100 mm (1.5 to 4 in.) thick. Allow compacted specimens to cool at normal room temperature on a clean, flat surface until cool to the touch. 6.3. Field-Produced Asphalt MixtureLoose Mix: 6.3.1. Obtain a sample of asphalt mixture in accordance with T 168. 2017 by the American Assoc
31、iation of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 324-5 AASHTO 6.3.2. Laboratory Compaction of SpecimensCompact either slab specimens or SGC cylindrical specimens in accordance with Section 6.2.6. 6.4. Field-Produced Aspha
32、lt MixtureField Compacted (Core/Slab Specimen): 6.4.1. Cutting Field Cores or Field Slab SpecimensField cores or field slab specimens consist of wet saw-cut compacted specimens taken from asphalt mixture pavements. Cut field cores 300 mm (12 in.), 250 mm (10 in.), or 150 mm (6 in.) in diameter. Cut
33、field slab specimens approximately 260 mm (10.25 in.) wide by 320 mm (12.5 in.) long. Use a slab specimen thickness of 38 to 100 mm (1.5 to 4 in.). The height of a field core or field slab specimen is typically 38 mm (1.5 in.), but may be adjusted to fit the specimen mounting system by wet saw-cutti
34、ng. Cut field cores in accordance with Section 6.4.2. Note 2Take care to load the sample so it is level to the surface of the mold. Trim the sample if it is too tall, or use shims if it is too short (supporting with plaster if needed). Calibrate the down pressure from the wheel to be 705 N (158 lb)
35、at the center, level to the top of the mold position. Even a small change in elevation will change the down pressure significantly. 6.4.2. Cutting SGC Cylindrical Specimens and Field CoresCut specimens after they have cooled to room temperature using a wet or dry saw. Saw the specimens along equal s
36、ecant lines (or chords) such that when joined together in the molds, there is no space between the cut edges. The amount of material sawed from the SGC cylindrical specimens may vary to achieve a gap width no greater than 7.5 mm (0.3 in.) between the molds. Note 3To cut specimens consistently may re
37、quire the use of a jig. 7. DETERMINING AIR VOID CONTENT 7.1. Determine the bulk specific gravity of the specimens in accordance with T 166. 7.2. Determine the maximum specific gravity of the mixture in accordance with T 209. 7.3. Determine the air void content of the specimens in accordance with T 2
38、69. The recommended target air void content is 7.0 0.5 percent for laboratory-compacted SGC cylindrical specimens and 7.0 1.0 percent for laboratory-compacted slab specimens. Field specimens may be tested at the air void content at which they are obtained. 8. PROCEDURE 8.1. Slab and Large Field Core
39、 Specimen MountingUse plaster of paris to rigidly mount the 300 mm (12 in.), 250 mm (10 in.), or slab specimens in the mounting trays. Mix the plaster at approximately a 1:1 ratio of plaster to water. Pour the plaster to a height equal to that of the specimen to fill the air space between the specim
40、en and the sides of the mounting tray. The slab specimen will be in direct contact with the mounting tray; however, plaster may flow underneath the specimen. The plaster underneath the specimen must not exceed 2 mm (0.08 in.). Allow the plaster at least 1 h to set. If using other mounting material,
41、it should be able to withstand 890 N (200 lb) of load without cracking. 8.2. SGC Cylindrical and Field Core Specimen MountingRigidly mount the 150-mm 5.91-in. or 152-mm 6-in. diameter samples in the mounting tray using HDPE molds meeting the dimensions outlined in Figure 2 or use plaster of paris. F
42、or HDPE molds, place the molds in the mounting tray and insert the cut specimens in the molds. Shim the molds in the mounting tray as necessary. Secure the molds into the mounting tray. If plaster of paris is used, pour the plaster to a height equal to that of the specimen to fill the air space betw
43、een the specimen and the sides of the mounting tray. The specimen will be in direct contact with the mounting tray; however, plaster 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 324-6 AASHTO
44、may flow underneath the specimen. The plaster underneath the specimen must not exceed 2 mm (0.08 in.) in thickness. Allow the plaster at least 1 h to set. Note 4Cores drilled with a 152-mm (6-in.) drill bit may not fit in the 150-mm (5.91-in.) HDPE mold and may require mounting in plaster of paris.
45、8.3. Place the mounting tray(s) with the test specimens into the device. Adjust the height of the specimen tray as recommended by the manufacturer, and secure by hand-tightening the bolts. 8.4. Turn the testing device and computer on. 8.5. Start the software used to communicate with the testing devi
46、ce. 8.6. Enter the pertinent project information and testing configuration requirements. 8.6.1. Select the test temperature based on the applicable specifications. 8.6.2. Select the maximum allowable rut depth based on the applicable specifications. 8.6.3. Select the maximum number of passes based o
47、n the applicable specifications. 8.6.4. Enter a start delay of 45 min to precondition the test specimens. The temperature of the specimens in the mounting tray will be the test temperature selected in Section 8.6.1 on completion of this preconditioning period. 8.7. Proceed to Section 8.8 to operate
48、the testing device in “Auto” mode. Proceed to Section 8.9 to operate the testing device in “Manual” mode. Note 5Perform the test in “Auto” mode for testing devices manufactured in the United States later than 1998, where software will automatically open and close the valves to fill and drain the wat
49、er bath. Perform the test in “Manual” mode for devices made available to the United States prior to 1998. 8.8. Performing the Test in Auto Mode: 8.8.1. Adjust the height of the LVDT in accordance with the manufacturers recommendations. Note 6The LVDT for each steel wheel is automatically zeroed at the start of the test. The software will display a zero at the start of the test. 8.8.2. If using cylindrical specimens, lower the wheels onto the edge of the test specimens such that a majority of the wheel is in
