1、Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA) AASHTO Designation: T 324-16 Release: Group 3 (August 2016) 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 AASH
2、TO Standard Method of Test for Hamburg Wheel-Track Testing of Compacted Hot Mix Asphalt (HMA) AASHTO Designation: T 324-16 Release: Group 3 (August 2016) 1. SCOPE 1.1. This test method describes a procedure for testing the rutting and moisture-susceptibility of hot mix asphalt (HMA) pavement samples
3、 in the Hamburg Wheel-Tracking Device. 1.2. The method describes 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 prepa
4、re 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 300 mm (12 in.), or saw-cut slab specimens may be tested. 1.3. The test method is used to dete
5、rmine the premature failure susceptibility of HMA due to weakness 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
6、 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 all of the safety concerns associated with its use. It is the responsibility of the user of this standard
7、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 Conditioning of Hot Mix Asphalt (HMA) T 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using
8、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 Dense and Open Asphalt Mixtures T 312, Preparing and Determining the Density of Asphalt Mixture Spec
9、imens by Means of the Superpave Gyratory Compactor 2.2. ASTM Standard: D6027, Standard Test Method for Calibrating Linear Displacement Transducers for Geotechnical Purposes (withdrawn 2013) 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplicatio
10、n is a violation of applicable law.TS-2c T 324-2 AASHTO 3. SIGNIFICANCE 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
11、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 deformation of the specimen, caused by the wheel loading, is measured. 4.2. The impression is plotted as a function of the number of w
12、heel passes. An abrupt increase in the rate of deformation may coincide 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 st
13、eel wheel over a test specimen. The load on the wheel is 705 4.5 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 spec
14、imen, is approximately 0.305 m/s (1 ft/s). 5.2. Temperature Control 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 Measureme
15、nt SystemA linear variable differential transducer (LVDT) device 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
16、 depth, without stopping the wheel, at least every 400 passes. Rut 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-co
17、ntacting solenoid that counts each wheel pass over the specimen. 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
18、 to the machine. The 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 minimum of 20 mm (0.8 in.) of free circulating water on all sides. 5.6. Cylindrical Specimen Mounting SystemAn assembly consisting of two
19、high-density polyethylene (HDPE) molds or plaster of paris, in accordance 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 i
20、n.) during testing and must suspend the specimen to provide a minimum of 20 mm (0.8 in.) of free circulating water on all sides. 2016 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 Figur
21、e 1Cylindrical Specimen Mounting System Figure 2Schematic of Cylindrical Specimen Mounting System 2016 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 hydr
22、aulic-powered unit that uses a series of vertically aligned steel plates to compact molded asphalt mixtures into flat, rectangular 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 G
23、yratory Compactor (SGC)And molds conforming to T 312. 5.11. Bowls, spoon, spatula, etc. 6. SPECIMEN PREPARATION 6.1. Number of Test SpecimensPrepare two test specimens for each test, either slab specimens or cylinders. 6.2. Laboratory-Produced HMA: 6.2.1. Batch mixture proportions in accordance with
24、 the desired job mix formula. 6.2.2. Use the 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 a
25、dd the correct percentage of asphalt binder. 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 fo
26、r mechanical properties in R 30. 6.2.5. Use the 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 spe
27、cimens or SGC cylindrical specimens. 6.2.6.1. 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 ma
28、ximum aggregate size, generally yielding a specimen 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 acc
29、ordance with T 312. 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 specimens to cool at normal room temperature on a clean, flat surface until cool to the touch. 6.3. Field-Produced HMALoo
30、se Mix: 6.3.1. Obtain a sample of HMA in accordance with T 168. 2016 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
31、 or SGC cylindrical specimens. 6.3.2.1. 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
32、aggregate size, generally yielding a specimen 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 accordanc
33、e with T 312. 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 specimens to cool at normal room temperature on a clean, flat surface until cool to the touch. 6.4. Field-Produced HMAField Com
34、pacted (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 HMA pavements. Cut field cores 300 mm (12 in.), 250 mm (10 in.), or 150 mm (6 in.) in diameter. Cut field slab specimens approximat
35、ely 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-cutting. Cut field cores in accordan
36、ce 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) at the center, level to the top
37、 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 a secant line (or chord) such that whe
38、n 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. 7. DETERMINING AIR VOID CONTENT 7.1. Determine the bulk specific gravity of the
39、 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 269. The recommended target air void content is 7.0 0.5 percent for laboratory-compacted SGC cylindrical
40、 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 Specimen MountingUse plaster of paris to rigidly mount the 300 mm (12 in.), 250 mm (10 in.), or slab s
41、pecimens 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 specimen and the sides of the mounting tray. The slab specimen will be in direct contact with the mounting tr
42、ay; however, plaster may flow underneath the specimen. The plaster underneath the specimen must not exceed 2 mm (0.08 in.). Allow the 2016 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
43、plaster at least 1 h to set. If using other mounting material, it should be able to withstand 890 N (200 lb) of load without 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 s
44、amples in the mounting tray meeting the dimensions outlined in Figure 2. If plaster of paris is used, pour the plaster to 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 tra
45、y; however, plaster 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. For HDPE molds, insert the cut specimens in the molds. Shim the molds in the mounting tray as necessary. Secure the molds int
46、o the mounting tray by hand-tightening the bolts of the edge plate. 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 o
47、n. 8.5. Start the software used to communicate with the testing device. 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 applicabl
48、e specifications. 8.6.3. Select the maximum number of passes based on the applicable specifications. 8.6.4. Enter a start 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 on completion of
49、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 the valves to fill and drain the water 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
