1、Standard Method of Test for Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor AASHTO Designation: T 312-15 American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001
2、TS-2d T 312-1 AASHTO Standard Method of Test for Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor AASHTO Designation: T 312-15 1. SCOPE 1.1. This standard covers the compaction of cylindrical specimens of asphalt mixtures using the Super
3、pave gyratory compactor. 1.2. 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 pract
4、ices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials R 30, Mixture Conditioning of Hot Mix Asphalt (HMA) R 35, Superpave Volumetric Design for Asphalt Mixtures R 47, Reduci
5、ng Samples of Hot Mix Asphalt (HMA) to Testing Size T 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) 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 275, Bul
6、k Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Paraffin-Coated Specimens T 316, Viscosity Determination of Asphalt Binder Using Rotational Viscometer T 344, Evaluation of Superpave Gyratory Compactor (SGC) Internal Angle of Gyration Using Simulated Loading 2.2. Other Standards: AN
7、SI/ASME B89.1.6, Measurement of Qualified Plain Internal Diameters for Use as Master Rings and Ring Gages ANSI/ASME B89.4.19, Performance Evaluation of Laser-Based Spherical Coordinate Measurement Systems ASME B46.1, Surface Texture (Surface Roughness, Waviness, and Lay) 2015 by the American Associa
8、tion of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 312-2 AASHTO 3. SIGNIFICANCE AND USE 3.1. This standard is used to prepare specimens for determining the mechanical and volumetric properties of asphalt mixtures. The specimen
9、s simulate the density, aggregate orientation, and structural characteristics obtained in the actual roadway when proper construction procedure is used in the placement of the paving mix. 3.2. This test method may be used to monitor the density of test specimens during their preparation. It may also
10、 be used for field control of an asphalt mixture production process. 4. APPARATUS 4.1. Superpave Gyratory CompactorAn electrohydraulic or electromechanical compactor with a ram and ram heads as described in Section 4.3. The axis of the ram shall be perpendicular to the platen of the compactor. The r
11、am shall apply and maintain a pressure of 600 18 kPa perpendicular to the cylindrical axis of the specimen during compaction (Note 1). The compactor shall tilt the specimen molds at an average internal angle of 20.2 0.35 mrad (1.16 0.02 degrees), determined in accordance with T 344. The compactor sh
12、all gyrate the specimen molds at a rate of 30.0 0.5 gyrations per minute throughout compaction. Note 1This stress calculates to 10 600 310 N total force for 150-mm specimens. 4.1.1. Specimen Height Measurement and Recording DeviceWhen specimen density is to be monitored during compaction, a means sh
13、all be provided to continuously measure and record the height of the specimen to the nearest 0.1 mm during compaction once per gyration. 4.1.2. The system may include a connected printer capable of printing test information, such as specimen height per gyration. In addition to a printer, the system
14、may include a computer and suitable software for data acquisition and reporting. 4.1.3. The loading system, ram, and pressure indicator shall be capable of providing and measuring a constant vertical pressure of 600 60 kPa during the first five gyrations, and 600 18 kPa during the remainder of the c
15、ompaction period. 4.2. Specimen MoldsSpecimen molds shall have steel walls that are at least 7.5 mm thick and are hardened to at least a Rockwell hardness of C48. The initial inside finish of the molds shall have a root mean square (rms) of 1.60 m or smoother when measured in accordance with ASME B4
16、6.1 (see Note 2). New molds shall be manufactured to have an inside diameter of 149.90 to 150.00 mm. The inside diameter of in-service molds shall not exceed 150.2 mm. Molds shall be at least 250 mm in length. The inside diameter and length of the molds shall be measured in accordance with Annex A.
17、Note 2One source of supply for a surface comparator, which is used to verify the rms value of 1.60 m, is GAR Electroforming, Danbury, Connecticut. 4.3. Ram Heads and End PlatesRam heads and end plates shall be fabricated from steel with a minimum Rockwell hardness of C48. The ram heads shall stay pe
18、rpendicular to their axis. The platen side of each end plate shall be flat and parallel to its face. All ram and end plate faces (the sides presented to the specimen) shall be flat to meet the smoothness requirement in Section 4.2 and shall have a diameter of 149.50 to 149.75 mm. 4.4. ThermometersAr
19、mored, glass, or dial-type thermometers with metal stems for determining the temperature of aggregates, binder, and HMA between 10 and 232C. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 312-3
20、AASHTO 4.5. BalanceA balance meeting the requirements of M 231, Class G 5, for determining the mass of aggregates, binder, and asphalt mixtures. 4.6. OvenAn oven, thermostatically controlled to 3C, for heating aggregates, binder, asphalt mixtures, and equipment as required. The oven shall be capable
21、 of maintaining the temperature required for mixture conditioning in accordance with R 30. 4.7. MiscellaneousFlat-bottom metal pans for heating aggregates, scoop for batching aggregates, containers (grill-type tins, beakers, containers for heating asphalt), large mixing spoon or small trowel, large
22、spatula, gloves for handling hot equipment, paper disks, mechanical mixer (optional), lubricating materials recommended by the compactor manufacturer. 4.8. MaintenanceIn addition to routine maintenance recommended by the manufacturer, check the Superpave gyratory compactors mechanical components for
23、 wear, and perform repair, as recommended by the manufacturer. 5. HAZARDS 5.1. Use standard safety precautions and protective clothing when handling hot materials and preparing test specimens. 6. STANDARDIZATION 6.1. Items requiring periodic verification of calibration include the ram pressure, angl
24、e of gyration, gyration frequency, LVDT (or other means used to continuously record the specimen height), and oven temperature. Verification of the mold and platen dimensions and the inside finish of the mold are also required. When the computer and software options are used, periodically verify the
25、 data-processing system output using a procedure designed for such purposes. Verification of calibration, system standardization, and quality checks may be performed by the manufacturer, other agencies providing such services, or in-house personnel. Frequency of verification shall follow the manufac
26、turers recommendations. 6.2. The angle of gyration refers to the internal angle (the tilt of the mold with respect to the end plate surface within the gyratory mold). The calibration of the internal angle of gyration shall be verified in accordance with T 344. 7. PREPARATION OF APPARATUS 7.1. Immedi
27、ately prior to the time when the asphalt mixture is ready for placement in the mold, turn on the main power for the compactor for the manufacturers required warm-up period. 7.2. Verify the machine settings are correct for angle, pressure, and number of gyrations. 7.3. Lubricate any bearing surfaces
28、as needed per the manufacturers instructions. 7.4. When specimen height is to be monitored, the following additional item of preparation is required. Immediately prior to the time when the asphalt mixture is ready for placement in the mold, turn on the device for measuring and recording the height o
29、f the specimen, and verify the readout is in the proper units, mm, and the recording device is ready. Prepare the computer, if used, to record the height data, and enter the header information for the specimen. 2015 by the American Association of State Highway and Transportation Officials.All rights
30、 reserved. Duplication is a violation of applicable law.TS-2d T 312-4 AASHTO 8. HMA MIXTURE PREPARATION 8.1. Laboratory Prepared: 8.1.1. Weigh the appropriate aggregate fractions into a separate pan, and combine them to the desired batch weight. The batch weight will vary based on the ultimate dispo
31、sition of the test specimens. If a target air void level is desired, as would be the case for Superpave mix analysis and performance specimens, batch weights will be adjusted to create a given density in a known volume. If the specimens are to be used for the determination of volumetric properties,
32、the batch weights will be adjusted to result in a compacted specimen having dimensions of 150 mm in diameter and 115 5 mm in height at the desired number of gyrations. Note 3It may be necessary to produce a trial specimen to achieve this height requirement. Generally, 4500 to 4700 g of aggregate are
33、 required to achieve this height for aggregates with combined bulk specific gravities of 2.550 to 2.700, respectively. 8.1.2. Place the aggregate and binder container in the oven, and heat them to the required mixing temperature. 8.1.2.1. The mixing temperature range is defined as the range of tempe
34、ratures where the unaged binder has a viscosity of 0.17 0.02 Pas when measured in accordance with T 316. Note 4Modified asphalts may not adhere to the equiviscosity requirements noted, and the manufacturers recommendations should be used to determine mixing and compaction temperatures. 8.1.3. Charge
35、 the mixing bowl 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. 8.1.4. Mix the aggregate and binder as quickly and thoroughly as possible to yield an asphalt
36、 mixture having a uniform distribution of binder. As an option, mechanical mixing may be used. 8.1.5. After completing the mixture preparation, perform the required mixture conditioning in accordance with R 30. 8.1.6. Place the compaction mold(s) and base plate(s) in an oven at the required compacti
37、on temperature for a minimum of 30 min prior to the estimated beginning of compaction (during the time the mixture is being conditioned in accordance with R 30). 8.1.7. Following the mixture conditioning period specified in R 30, if the mixture is at the compaction temperature, proceed immediately w
38、ith the compaction procedure as outlined in Section 9. If the compaction temperature is different from the mixture conditioning temperature used in accordance with R 30, place the mix in another oven at the compaction temperature for a brief time (maximum of 30 min) to achieve the required temperatu
39、re. 8.1.7.1. The compaction temperature is the midpoint of the range of temperatures where the unaged binder has a viscosity of 0.28 0.03 Pas when measured in accordance with T 316. (See Note 4.) 8.2. Plant Produced: 8.2.1. Place the compaction mold(s) and base plates(s) in an oven at the required c
40、ompaction temperature (see Section 8.1.7.1). 8.2.2. Obtain the sample in accordance with T 168. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 312-5 AASHTO 8.2.3. Reduce the sample in accordance
41、 with R 47. 8.2.4. Place the sample into a pan to a uniform thickness. 8.2.5. Bring the HMA to the compaction temperature range by careful, uniform heating in an oven immediately prior to molding. 9. COMPACTION PROCEDURE 9.1. When the compaction temperature is achieved, remove the heated mold, base
42、plate, and upper plate (if required) from the oven. Place the base plate and a paper disk in the bottom of the mold. 9.2. Place the mixture into the mold in one lift. Care should be taken to avoid segregation in the mold. After all the mix is in the mold, level the mix, and place another paper disk
43、and upper plate (if required) on top of the leveled material. 9.3. Load the charged mold into the compactor, and center the loading ram. 9.4. Apply a pressure of 600 18 kPa on the specimen. 9.5. Apply a 20.2 0.35 mrad (1.16 0.02 degrees) average internal angle to the mold assembly, and begin the gyr
44、atory compaction. 9.6. Allow the compaction to proceed until the desired number of gyrations specified in R 35 is reached and the gyratory mechanism shuts off. 9.7. Remove the angle from the mold assembly, remove the ram pressure, and retract the loading ram in the order specified by the SGC manufac
45、turer (the preceding steps may be done automatically by the compactor on some models of SGCs). Remove the mold from the compactor (if required), and extrude the specimen from the mold. Note 5No additional gyrations with the angle removed are required unless specifically called for in another standar
46、d referencing T 312. The extruded specimen may not be a right angle cylinder. Specimen ends may need to be sawed to conform to the requirements of specific performance tests. Note 6The specimens can be extruded from the mold immediately after compaction for most asphalt mixtures. However, a cooling
47、period of 5 to 10 min in front of a fan may be necessary before extruding some specimens to ensure the specimens are not damaged. 9.8. Remove the paper disks from the top and bottom of the specimens. Note 7Before reusing the mold, place it in an oven for at least 5 min. The use of multiple molds wil
48、l speed up the compaction process. 10. DENSITY PROCEDURE 10.1. Determine the maximum specific gravity (Gmm) of the loose mix in accordance with T 209 using a companion sample. The companion sample shall be conditioned to the same extent as the compaction sample. 10.2. Determine the bulk specific gra
49、vity (Gmb) of the specimen in accordance with T 166 or T 275 as appropriate. 10.3. When the specimen height is to be monitored, record the specimen height to the nearest 0.1 mm after each revolution. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d T 312-6 AASHTO 11. DENSITY CALCULATIONS 11.1. Calculate the uncorrected relative density (%Gmmux) at any point in the compaction process using the following eq
