1、Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA) AASHTO Designation: T 324-14 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2c T 324-1 AASHTO Standard Method of Test for
2、Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA) AASHTO Designation: T 324-14 1. SCOPE 1.1. This test method describes a procedure for testing the rutting and moisture-susceptibility of hot mix asphalt (HMA) pavement samples in the Hamburg Wheel-Tracking Device. 1.2. The method describ
3、es the testing of submerged, compacted HMA in a reciprocating rolling-wheel device. This test provides information about the rate of permanent deformation from a moving, concentrated load. A laboratory compactor has been designed to prepare slab specimens. Also, the Superpavegyratory compactor (SGC)
4、 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 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 HMA due to weakne
5、ss in the aggregate structure, inadequate binder stiffness, or moisture damage. This test method measures the rut depth and number 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
6、 loading. 1.5. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address 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 determ
7、ine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 30, Mixture Conditioning of Hot Mix Asphalt (HMA) T 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens T 168, Sampling Bituminous Pavi
8、ng Mixtures T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA) T 269, Percent Air Voids in Compacted Dense and Open Asphalt Mixtures T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor 2.2. ASTM St
9、andard: D 6027, Standard Practice for Calibrating Linear Displacement Transducers for Geotechnical Purposes (Withdrawn 2013) 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c T 324-2 AASHTO 3. SIGNIF
10、ICANCE AND USE 3.1. This test measures the rutting and moisture susceptibility of an HMA specimen. 4. SUMMARY OF METHOD 4.1. A laboratory-compacted specimen of HMA, a saw-cut slab specimen, or a core taken from a compacted pavement is repetitively loaded using a reciprocating steel wheel. The specim
11、en is submerged in a temperature-controlled water bath at a temperature specified by the agency. The deformation 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 co
12、incide with stripping of the asphalt binder from the aggregate in the HMA specimen. 5. APPARATUS 5.1. Hamburg Wheel-Tracking MachineAn electrically powered machine capable of moving a 203.2-mm (8-in.) diameter, 47-mm (1.85-in.) wide steel wheel over a test specimen. The load on the wheel is 705 4.5
13、N (158 1.0 lb). The wheel reciprocates over the specimen, 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 Contr
14、ol SystemA water bath capable of controlling the temperature 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
15、capable of measuring the depth of the impression (rut) of 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. Ru
16、t depth is expressed as a function of the wheel passes. Note 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.
17、The signal from this counter is coupled to the wheel impression 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 th
18、e 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. 5.6. Cylindrical Specimen Mounting SystemAn assembly consisting of two high-density polyethylene (HDPE) molds or plaster of paris in acc
19、ordance with Section 8 to secure the specimen (as shown in Figures 1 and 2) placed in a stainless steel tray that is mounted rigidly to the machine. This mounting system must restrict shifting of the specimen to within 0.5 mm (0.02 in.) during testing and must suspend the specimen to provide a minim
20、um of 20 mm (0.8 in.) of free circulating water on all sides. 2014 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 Figure 1Cylindrical Specimen Mounting System Figure 2Schematic of Cylind
21、rical Specimen Mounting System High-Density Polyethlylene MoldsThickness = 60 1 mm (2.36 0.04 in.) or 40 1 mm (1.57 0.04 in.)150mm(6 in.)150mm(6 in.)*Varies*Varies*Varies*VariesGap Width with HDPE Molds,7.5 mm (0.30 in.) maximum* Dimension may vary depending on manufacturer.No Gap Required withPlast
22、er of Paris 2014 by the American Association 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 mo
23、lded asphalt mixtures into flat, rectangular slabs of predetermined thickness and density. 5.8. BalanceBalance of 12 000-g capacity, accurate to 0.1 g. 5.9. OvensOvens for heating aggregate and asphalt binders. 5.10. Superpave Gyratory CompactorSuperpave gyratory compactor (SGC) and molds conforming
24、 to T 312. 5.11. Bowls, spoon, spatula, etc. 6. SPECIMEN PREPARATION 6.1. Number of Test SpecimensPrepare two test specimens for each testeither slab specimens or cylinders. 6.2. Laboratory-Produced HMA: 6.2.1. Batch mixture proportions in accordance with the desired job mix formula. 6.2.2. Use the
25、mixing temperature at which the asphalt binder achieves a viscosity of 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.
26、Mix the materials to coat all aggregates thoroughly. (Wet-mix the aggregates 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 t
27、he compaction temperature at which the asphalt binder achieves a viscosity 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.
28、 Compacting Slab SpecimensHeat molds and tools to compaction temperature. 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 sp
29、ecimen 38 to 100 mm (1.5 to 4 in.) thick. Allow compacted slab specimens 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 b
30、e at least twice the nominal maximum aggregate size, generally yielding 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 HMALoose Mix: 6.3.1. Obtain a sample of HMA in acco
31、rdance with T 168. 2014 by the American Association 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. 6.3.2.1. Compa
32、cting Slab SpecimensHeat molds and tools to compaction temperature. 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
33、 38 to 100 mm (1.5 to 4 in.) thick. Allow compacted slab specimens to cool at normal room temperature on a clean, flat surface until cool to the touch. 6.3.2.2. Compacting SGC Cylindrical SpecimensCompact two 150-mm (6-in.) diameter specimens in accordance with T 312. Specimen thickness must be at l
34、east twice the nominal maximum aggregate size, generally yielding 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. 6.4. Field-Produced HMAField Compacted (Core/Slab Specimen): 6.4.1. Cutting F
35、ield Cores or Field Slab SpecimensField cores or field slab specimens consist of wet saw-cut compacted specimens taken from HMA pavements. Cut field cores 300 mm (12 in.), 250 mm (10 in.), or 150 mm (6 in.) in diameter. Cut field slab specimens approximately 260 mm (10.25 in.) wide by 320 mm (12.5 i
36、n.) 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-cutting. Cut field cores in accordance with Section 6.4.2. Note 2Take care to loa
37、d 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) at the center, level to the top of the mold position. Even a small change in
38、 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 a secant line (or chord) such that when joined together in the molds, there is no s
39、pace 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. 7. DETERMINING AIR VOID CONTENT 7.1. Determine the bulk specific gravity of the specimens in accordance with T 166. 7.2. Det
40、ermine 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 269. The recommended target air void content is 7.0 1.0 percent for laboratory-compacted specimens. Field specimens may be tested at the air void con
41、tent at which they are obtained. 8. PROCEDURE 8.1. Slab and Large Field Core 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 h
42、eight equal to that of the specimen to fill the air space between the specimen 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.
43、). Allow the 2014 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 plaster at least 1 h to set. If using other mounting material, it should be able to withstand 890 N (200 lb) of load with
44、out cracking. 8.2. SGC Cylindrical and Field Core Specimen MountingPlace the HDPE molds in the mounting tray or use plaster of paris to rigidly mount the 150-mm (6-in.) diameter samples in the mounting tray meeting the dimensions outlined in Figure 2. If plaster of paris is used, pour the plaster to
45、 a height equal to that of the specimen to fill the air space between the specimen and the sides of the mounting tray. The 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.)
46、 in thickness. Allow the plaster at least 1 h to set. For HDPE molds, insert the cut specimens in the molds. Shim the molds in the mounting tray as necessary. Secure the molds into the mounting tray by hand-tightening the bolts of the edge plate. 8.3. Place the mounting tray(s) with the test specime
47、ns 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 device. 8.6. Enter the pertinent project information and
48、testing configuration requirements. 8.6.1. Select the test temperature based upon the applicable specifications. 8.6.2. Select the maximum allowable rut depth based upon the applicable specifications. 8.6.3. Select the maximum number of passes based on the applicable specifications. 8.6.4. Enter a s
49、tart delay of 30 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 upon completion of this preconditioning period. 8.7. Proceed to Section 8.8 to operate the testing device in “Auto” mode. Proceed to Section 8.9 to operate the testing device in “Manual” mode. Note 3Perform the test in “Auto” mode for testing devices manufactured in the United States later than 1998, where software will automatically open and close th
