1、Standard Method of Test for Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT) AASHTO Designation: TP 79-151,2American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington,
2、D.C. 20001 TS-2d TP 79-1 AASHTO Standard Method of Test for Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT) AASHTO Designation: TP 79-151,21. SCOPE 1.1. This standard describes test methods for measuring the dynamic modulus and
3、 flow number for asphalt mixtures using the Asphalt Mixture Performance Tester (AMPT). This practice is intended for dense- and gap-graded mixtures with nominal-maximum aggregate sizes up to 37.5 mm. 1.2. This standard may involve hazardous materials, operations, and equipment. This standard does no
4、t 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 determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standard: PP
5、 60, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) 2.2. Other Publication: Equipment Specification for the Simple Performance Test System, Version 3.0, Prepared for National Cooperative Highway Research Program (NCHRP), October 16, 2007 3. TERMINO
6、LOGY 3.1. Definitions: 3.1.1. confining pressurethe stress applied to all surfaces in a confined test. 3.1.2. deviator stressthe difference between the total axial stress and the confining pressure in a confined test. 3.1.3. dynamic modulus, |E*|the absolute value of the complex modulus calculated b
7、y dividing the peak-to-peak stress by the peak-to-peak strain for a material subjected to a sinusoidal loading. 3.1.4. flow numberthe number of load cycles corresponding to the minimum rate of change of permanent axial strain during a repeated-load test. 2015 by the American Association of State Hig
8、hway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 79-2 AASHTO 3.1.5. phase angle, the angle in degrees between a sinusoidally applied stress and the resulting strain in a controlled stress test. 3.1.6. permanent deformationthe nonrecovered d
9、eformation in a repeated-load test. 4. SUMMARY OF METHOD 4.1. This test method describes procedures for measuring the dynamic modulus and flow number for asphalt mixtures. 4.2. In the dynamic modulus procedure, a specimen at a specific test temperature is subjected to a controlled sinusoidal (havers
10、ine) compressive stress of various frequencies. The applied stresses and resulting axial strains are measured as a function of time and used to calculate the dynamic modulus and phase angle. 4.3. In the flow number procedure, a specimen at a specific test temperature is subjected to a repeated haver
11、sine axial compressive load pulse of 0.1 s every 1.0 s. The test may be conducted with or without confining pressure. The resulting permanent axial strains are measured as a function of the load cycles and numerically differentiated to calculate the flow number. The flow number is defined as the num
12、ber of load cycles corresponding to the minimum rate of change of permanent axial strain. 5. SIGNIFICANCE AND USE 5.1. The dynamic modulus is a performance-related property that can be used for mixture evaluation and for characterizing the stiffness of asphalt mixtures for mechanistic-empirical pave
13、ment design. 5.2. The flow number is a property related to the resistance of asphalt mixtures to permanent deformation. It can be used to evaluate and design asphalt mixtures with specific resistance to permanent deformation. 6. APPARATUS 6.1. Specimen Fabrication EquipmentFor fabricating dynamic mo
14、dulus test specimens as described in PP 60. 6.2. Dynamic Modulus Test SystemMeeting the requirements of the equipment specification for the Simple Performance Test (SPT) System, Version 3.0, except for the following provisions: In the referenced equipment specification, Sections 10.7 and 11.3 shall
15、require a temperature sensor range of 0 to 75C (32 to 167F) and Section 11.1 shall require a temperature control range from 4 to 70C (39 to 158F) 6.3. Conditioning ChamberAn environmental chamber for conditioning the test specimens to the desired testing temperature. The environmental chamber shall
16、be capable of controlling the temperature of the specimen over a temperature range from 4 to 70C to an accuracy of 0.5C. The chamber shall be large enough to accommodate the number of specimens to be tested plus a “dummy” specimen with a temperature sensor mounted in the center for temperature verif
17、ication. Note 1The temperature range required for the Dynamic Modulus Test System and the Conditioning Chamber is a function of the anticipated test temperature. The temperature control range provided in Sections 6.2 and 6.3 is intended to be inclusive of all areas of the U.S. In many climatic regio
18、ns, it may not be necessary to have equipment capable of controlling the temperature up to 70C. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 79-3 AASHTO 6.4. TFE-Fluorocarbon Sheet0.25 mm thi
19、ck, to be used as a friction reducer between the specimen and the loading platens in the dynamic modulus test. 6.5. Latex Membranes100-mm diameter by 0.3 mm thick, for use in confined tests and for manufacturing “greased double latex” friction reducers to be used between the specimen and the loading
20、 platens in the dynamic modulus and flow number tests. 6.6. Silicone GreaseDow Corning “Stopcock Grease” or equivalent, for manufacturing greased double latex friction reducers. 6.7. BalanceCapable of determining mass to the nearest 0.01 g. The balance is used to determine the mass of silicone greas
21、e during fabrication of greased double latex friction reducers. 7. HAZARDS 7.1. This practice and associated standards involve handling of hot asphalt binder, aggregates, and asphalt mixtures. It also includes the use of sawing and coring machinery and servohydraulic testing equipment. Use standard
22、safety precautions, equipment, and clothing when handling hot materials and operating machinery. 8. STANDARDIZATION 8.1. Verification with Proving Ring: 8.1.1. Verify the normal operation of the AMPT weekly or at the beginning of a new testing program using the manufacturer-provided proving ring. Pe
23、rform a dynamic modulus test on the proving ring using a target strain of 100 microstrain at 1.0 Hz. The dynamic modulus of the proving ring should be within 3 percent of the value obtained on the proving ring for the same testing conditions during the last calibration. 8.2. Calibration: 8.2.1. The
24、following systems on the AMPT shall be calibrated annually, when the AMPT system is moved, or when any of its components are changed: Load Measuring System Actuator Displacement Measuring System Specimen-Mounted Deformation Measuring System Confining Pressure Measuring System Temperature Measuring S
25、ystem Methods for calibration of each of these systems are included in Annex B. 9. PROCEDURE ADYNAMIC MODULUS TEST 9.1. Test Specimen Fabrication: 9.1.1. Testing shall be performed on 100-mm diameter by 150-mm tall test specimens fabricated in accordance with PP 60. 9.1.2. Prepare at least two test
26、specimens at the target air void content 0.5 percent and with the aging condition in accordance with PP 60. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 79-4 AASHTO Note 2The number of specim
27、ens to test depends on the desired accuracy of the analysis. Refer to Table 4 for guidance on the reproducibility of dynamic modulus and phase angle measurements. 9.2. Test Specimen Instrumentation (Standard Glued-Gauge-Point System): 9.2.1. Attach the gauge points to the specimen in accordance with
28、 the manufacturers instructions. 9.2.2. Confirm that the gauge length is 70 mm 1 mm, measured center-to-center of the gauge points. 9.3. Loading Platens and End-Friction Reducers: 9.3.1. For the dynamic modulus test, the top platen shall be free to rotate. 9.3.2. Either greased double latex or TFE f
29、luorocarbon end-friction reducers can be used in the dynamic modulus test. 9.3.2.1. Teflon end-friction reducers are made from 0.25-mm thick TFE fluorocarbon sheet, cut to a size slightly larger than the loading platen. 9.3.2.2. Greased double latex friction reducers are fabricated from 0.3-mm thick
30、 latex membranes as described in Annex A. 9.4. Procedure: 9.4.1. Unconfined Tests: 9.4.1.1. Place the specimens to be tested in the environmental chamber with the “dummy” specimen and monitor the temperature of the dummy specimen to determine when testing can begin. 9.4.1.2. Place platens and fricti
31、on reducers inside the testing chamber. Turn on the AMPT, set the temperature control to the desired testing temperature, and allow the testing chamber to equilibrate at the testing temperature for at least 1 h. 9.4.1.3. When the dummy specimen and the testing chamber reach the target temperature, o
32、pen the testing chamber. Remove a test specimen from the conditioning chamber and quickly place it in the testing chamber. 9.4.1.4. Assemble the specimen to be tested with platens in the following order from bottom to top: bottom loading platen, bottom friction reducer, specimen, top friction reduce
33、r, and top loading platen. 9.4.1.5. Install the specimen-mounted deformation measuring system on the gauge points per the manufacturers instructions. Ensure that the deformation measuring system is within its calibrated range. Ensure that the top loading platen is free to rotate during loading. 9.4.
34、1.6. Close the testing chamber and allow the chamber temperature to return to the testing temperature. 9.4.1.7. Procedures in Sections 9.4.1.3 through 9.4.1.6, including the return of the test chamber to the target temperature, shall be completed in 5 min. 9.4.1.8. Enter the required identification
35、and control information into the dynamic modulus software. 9.4.1.9. Follow the software prompts to begin the test. The AMPT will automatically unload when the test is complete and will display the test data and data quality indicators. 2015 by the American Association of State Highway and Transporta
36、tion Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 79-5 AASHTO 9.4.1.10. Review the data quality indicators as discussed in Section 9.5. Retest specimens with data quality indicators above the values specified in Section 9.5. 9.4.1.11. Once acceptable data have
37、 been collected, open the test chamber and remove the tested specimen. 9.4.1.12. Repeat procedures in Sections 9.4.1.3 through 9.4.1.11 for the remaining test specimens. 9.4.2. Confined Tests: 9.4.2.1. Assemble each specimen to be tested with the platens and membrane as follows: place the bottom fri
38、ction reducer and the specimen on the bottom platen. Stretch the membrane over the specimen and bottom loading platen. Install the lower O-ring seal. Place the top friction reducer and top platen on top of the specimen and stretch the membrane over the top platen. Install the upper O-ring seal. When
39、 performing confined tests, the specimen must be vented to atmospheric pressure through the drainage lines. Ensure that the friction reducers have holes to allow air to be vented from inside the membrane. 9.4.2.2. Encase the “dummy” specimen in a membrane. 9.4.2.3. Place the specimen and platen asse
40、mbly in the environmental chamber with the dummy specimen and monitor the temperature of the dummy specimen to determine when testing can begin. 9.4.2.4. Turn on the AMPT, set the temperature control to the desired testing temperature, and allow the testing chamber to equilibrate at the testing temp
41、erature for at least 1 h. 9.4.2.5. When the dummy specimen and the testing chamber reach the target temperature, open the testing chamber. Remove a test specimen and platen assembly and quickly place it in the testing chamber. When performing confined tests, the specimen must be vented to atmospheri
42、c pressure through the drainage lines. Properly connect the drainage lines to the loading platens, and ensure that they are vented to atmospheric pressure through the bubble chamber to identify leaks. 9.4.2.6. Install the specimen-mounted deformation measuring system outside the membrane on the gaug
43、e points per the manufacturers instructions. Ensure that the deformation measuring system is within its calibrated range. Ensure that the top loading platen is free to rotate during loading. 9.4.2.7. Close the testing chamber, and allow the chamber temperature to return to the testing temperature. 9
44、.4.2.8. Procedures in Sections 9.4.2.5 through 9.4.2.7, including the return of the test chamber to the target temperature, shall be completed in 5 min. 9.4.2.9. Enter the required identification and control information into the dynamic modulus software. 9.4.2.10. Follow the software prompts to begi
45、n the test. The AMPT will automatically unload when the test is complete and will display the test data and data quality indicators. 9.4.2.11. Review the data quality indicators as discussed in Section 9.5. Retest specimens with data quality indicators above the values specified in Section 9.5. 9.4.
46、2.12. Once acceptable data have been collected, open the test chamber and remove the tested specimen. 9.4.2.13. Repeat procedures in Sections 9.4.2.3 through 9.4.2.12 for the remaining test specimens. 9.5. Computations and Data Quality: 2015 by the American Association of State Highway and Transport
47、ation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 79-6 AASHTO 9.5.1. The calculation of dynamic modulus, phase angle, and the data quality indicators is performed automatically by the AMPT software. 9.5.2. Accept only test data meeting the data quality statis
48、tics given in Table 1. Table 2 summarizes actions that can be taken to improve the data quality statistic. Repeat tests as necessary to obtain test data meeting the data quality statistics requirements. Table 1Data Quality Statistics Requirements Data Quality Statistic Limit Deformation drift In dir
49、ection of applied load Peak-to-peak strain 75 to 125 microstrain for unconfined tests 85 to 115 microstrain for confined tests Load standard error 10% Deformation standard error 10% Deformation uniformity 30% Phase uniformity 3 Note 3The data quality statistics in Table 1 are reported by the AMPT. If a dynamic modulus test system other than the AMPT is used, refer to the equipment specification for the Simple Performance Test (SPT) System, Version 3.0, for algorithms for the computation of dynamic modulus, phase angle, and data quality
