1、Standard Method of Test for Preparation of Test Specimens of Hot Mix Asphalt (HMA) by Means of California Kneading Compactor AASHTO Designation: T 247-10 (2015) ASTM Designation: D1561-92 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Wash
2、ington, D.C. 20001 TS-2d T 247-1 AASHTO Standard Method of Test for Preparation of Test Specimens of Hot Mix Asphalt (HMA) by Means of California Kneading Compactor AASHTO Designation: T 247-10 (2015) ASTM Designation: D1561-92 1. SCOPE 1.1. The method covers the compaction of test specimens of hot
3、mix asphalt (HMA) by means of a mechanical compactor that imparts a kneading action to the test specimens by a series of individual impressions made with a ram. 1.2. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety
4、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 prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 30, Mixture Conditioning of H
5、ot Mix Asphalt (HMA) T 246, Resistance to Deformation and Cohesion of Hot Mix Asphalt (HMA) by Means of Hveem Apparatus T 316, Viscosity Determination of Asphalt Binder Using Rotational Viscometer 3. APPARATUS 3.1. California Kneading CompactorMechanical kneading compactor, as shown in Figure 1,1for
6、 consolidating test specimens. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 247-2 AASHTO Figure 1California Kneading Compactor Note 1Kneading compactors, which on standardization develop a tra
7、ce curve similar to that of the California kneading compactor, shall be considered acceptable under this test method. Optionally, any kneading compactor capable of fabricating specimens that will provide stabilometer values equivalent to those obtained from the California kneading compactor shall be
8、 acceptable for use under this test method. The supplier has the responsibility of furnishing those substantiating data for his device. Note 2Curves are considered within standardization when they show the same peak pressure and dwell time in load time trace obtained in the calibration procedure. No
9、te 3This compactor shall be considered in standardization when the peak momentary load applied to a test specimen is held within 5 percent of the intended foot pressure (within the range from 2.4 to 3.4 MPa (350 to 500 psi). Note 4The stabilometer values from replicate specimens fabricated by T 247
10、and tested in accordance with T 246 shall fall within a range of three units for all dense-graded HMA mixtures containing aggregates not larger than 12.5 mm (1/2in.) and within a range of four units for coarser-graded HMA mixtures containing up to 25.0-mm (1-in.) maximum-sized aggregates. 3.2. Compa
11、ctor FootA ram having a face shaped as shown in Figure 2, and having an area of approximately 20.059 cm2(3.1 in.2). 3.3. Mold Holder, Funnel, and Feeder TroughAs shown in Figure 3. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a vi
12、olation of applicable law.TS-2d T 247-3 AASHTO Figure 2Face of Compactor Ram Figure 3Funnel, Feeder Trough, and Mold Assembly of the California Kneading Compactor 3.4. MoldsMolding cylinders for 101.60 0.13 mm (4.000 0.005 in.) in inside diameter by 127 mm (5 in.) in height. A minimum of three such
13、compaction molds is recommended. Dimensional Limits, cm (in.)Min MaxDistance across Foot,3 Measurements 5.189 5.289120 Apart (2.042) (2.082)120 TypRTyp5.080 cm(2in.)RTyp0.635 cm( 1/4 in.)RTyp2.302 cm(29/32in.)RTyp2.778 cm(13/32in.) 2015 by the American Association of State Highway and Transportation
14、 Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 247-4 AASHTO 3.5. RodRound-nose steel rod, 9.5 mm (3/8in.) in diameter by 406 mm (16 in.) long. 3.6. Paper DisksHeavy paper disks, 102 mm (4 in.) in diameter. 3.7. ShimSteel shim, 6.4 mm (1/4in.) thick, 19 mm (3/4in
15、.) wide, and 64 mm (21/2in.) long. 3.8. Metal FollowersTwo metal followers, 101.2 0.11 mm (3.985 0.005 in.) in diameter; one 140 mm (5.5 in.) high, the other 38.1 mm (1.5 in.) high. 3.9. Testing MachineA compression testing machine having a minimum capacity of 222 kN (50,000 lbf). 3.10. OvensElectri
16、c ovens capable of maintaining temperatures of 60 3C (140 5F) and 110 3C (230 5F). 3.11. BalanceA balance having a capacity of 5 kg or more and sensitive to 1.0 g or less for determining the mass of the mixture. 3.12. Measuring DeviceA device for measuring the height of the specimen to the nearest 0
17、.3 mm (0.01 in.). 3.13. Sample Mixing ApparatusSuitable equipment is required for mixing the aggregate and the asphalt binder. Hand mixing is permissible but mechanical mixing is recommended.23.14. Sample SplitterRiffle-type. 3.15. Miscellaneous ApparatusThermometers, trowels, spatulas, scoops, glov
18、es, and metal pans. Note 5Caution: Rough interior of molds can cause a difference in test results. 4. TEST SPECIMENS 4.1. Selection of Binder Content for SpecimensDetermine the theoretical or estimated optimum amount of bitumen for the aggregate (Note 6). On normal materials, conduct laboratory test
19、s for a minimum of three binder contents, one above, one below, and one at the theoretical or estimated optimum content. The incremental change of binder content should be 0.5 percent. For extremely critical mixes, lower the incremental change of binder content to 0.3 percent, and increase the numbe
20、r of tests to a minimum of five. Conversely, for highly absorptive aggregates, increase the incremental change of binder content to 1.0 percent, and reduce the number of tests to three. Express the percentage of the binder as a percentage of the dry weight of the aggregate. Note 6The optimum amount
21、of binder for the aggregate may be determined by the method commonly employed by the laboratory. A method that has been found suitable is the centrifuge kerosene equivalent method. 4.2. Preparation of AggregatesObtain a sieve analysis and specific gravity determination on the fine and coarse aggrega
22、te (aggregate shall be separated by means of a 4.75-mm (No. 4) sieve). Separate the aggregate into the various size fractions necessary for accurately recombining into test mixtures conforming to specified grading requirements. 4.3. Preparation of MixturesCombine the moisture-free aggregates into ba
23、tches weighing 1200 g. (Every effort should be made to fabricate test specimens 64 3 mm (2.5 0.1 in.) in height.) The mixing temperature range is defined as the range of temperatures where the unaged binder has a viscosity of 0.17 0.02 Pas when measured in accordance with T 316. Charge the mixing bo
24、wl with the heated aggregate from one pan and dry-mix thoroughly. Form a crater in the dry-blended aggregate, and weigh the required amount of binder into the mix. Immediately initiate mixing. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplica
25、tion is a violation of applicable law.TS-2d T 247-5 AASHTO Mix the aggregate and binder as quickly and thoroughly as possible to yield HMA having a uniform distribution of binder. As an option, mechanical mixing may be used. Note 7Modified binders may not adhere to the equiviscosity requirements not
26、ed, and the manufacturers recommendations should be used to determine mixing and compaction temperatures. 5. PROCEDURE 5.1. TemperaturesAfter completing the mixture preparation, perform the required mixture conditioning in accordance with R 30. 5.2. Molding SpecimensThe mixture and molds shall be br
27、ought to compaction temperature prior to molding operations. Place the compaction mold in position in the mold holder, and insert a paper disk, 102 mm (4 in.) in diameter, to cover the base plate of the mold holder. Place a steel shim under the edge of the mold temporarily in order for the base plat
28、e of the mold holder to act as a free-fitting plunger during the compaction operation. Weigh out the required amount of HMA mixture for one specimen at the specified temperature and place it in the insulated feeder trough, which shall have been preheated to the approximate compaction temperature for
29、 the HMA mixture. Spread the HMA mixture uniformly on the feeder trough to ensure uniformity when transferring it to the mold. By means of a paddle of suitable dimensions to fit the cross-section of the trough, push one half of the mixture into the mold. Preheat the round-nose rod. Rod the one-half
30、portion of the HMA mixture 20 times in the center of mass and 20 times around the edge by means of the round-nose rod. Transfer the remainder of the sample to the mold and repeat the rodding procedure. Place the mold and assembly into position on the California kneading compactor. By means of the va
31、riable transformer controlling the heater, maintain the compactor foot sufficiently hot to prevent the HMA mixture from adhering to it. Apply approximately 20 tamping blows at a pressure of 1.7 MPa (250 psi). The number of tamping blows will vary, depending upon the type of the HMA mixture, the purp
32、ose being to form the HMA mixture into a semicompacted condition so that it will not be unduly disturbed by the full pressure of 3.4 MPa (500 psi). After semicompaction has been accomplished, remove the shim and release the mold-tightening screw sufficiently to permit free “up and down” movement of
33、the mold. Increase the compactor foot pressure to 3.4 MPa (500 psi), and apply 150 tamping blows to complete compaction. Note 8When testing referee samples for the purpose of qualifying a compactor, use only material for the test specimens that will compact under the maximum foot pressure prescribed
34、 in Section 4.2 without visible movement, distortion, or penetration of the compactor foot. Note 9In some instances where sandy or unstable material is involved, it may not be possible to accomplish the compaction in the kneading compactor because of undue movement of the mixture under the compactor
35、 foot. In these instances, use a 178-kN (40,000 lbf) static load (for a 102-mm (4-in.) diameter specimen) applied by the double plunger method in which a free-fitting plunger is placed on both the bottom and top of the test specimen. Apply the load at the rate of 1.3 mm (0.05 in.)/min, and hold for
36、30 5 s. 5.3. Application of Static LoadAfter compaction in the California kneading compactor, place the mold and the specimen in an oven at 60C (140F) for 1.5 h prior to applying the static “leveling off” load: 5.3.1. The “leveling off” load shall consist of the application of a static load of 6.9 M
37、Pa (1000 psi) in a compression testing machine. Apply the load by the double plunger method in which metal followers are employed as free-fitting plungers on the top and bottom of the specimen. After releasing the “leveling off” load, measure the height of the specimen to the nearest 0.25 mm (0.01 i
38、n.); record the measurement, and return the specimen in the mold to the 60C (140F) oven in order to retain temperature for testing. Complete testing of the specimens according to T 246 within 3 h of returning the specimens to the oven. 2015 by the American Association of State Highway and Transporta
39、tion Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 247-6 AASHTO Note 10A push-out device for removing the specimen is described in T 246. The temperature of the specimen and the method of transfer from the mold to the stabilometer are given in Section 5.2 of T 2
40、46. 6. REPORT 6.1. The report shall include the following: 6.1.1. Height of the specimen, and 6.1.2. Temperature of compaction in the California kneading compactor. 1Blueprints of detailed drawings of the apparatus illustrated in Figure 1 are available at a nominal cost from the American Society for
41、 Testing and Materials, 1916 Race St., Philadelphia, PA 19103. Request Adjunct No. 12-415610-00. 2A mechanical mixing apparatus capable of mixing simultaneously from two to five batches has been developed by the California State Department of Public Works, Division of Highways. Working drawings are
42、available at a nominal cost from the American Society for Testing and Materials, 100 Barr Harbor Dr., West Conshohocken, PA 19428-2959. Request Adjunct No. 12-415600-20. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
