1、Standard Method of Test for Determining the Damage Characteristic Curve and Failure Criterion Using the Asphalt Mixture Performance Tester (AMPT) Cyclic Fatigue Test AASHTO Designation: TP 107-181 Technical Section: 2d,Bituminous Materials Release: Group 3 (August) American Association of State High
2、way and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2d TP 107-1 AASHTO Standard Method of Test for Determining the Damage Characteristic Curve and Failure Criterion Using the Asphalt Mixture Performance Tester (AMPT) Cyclic Fatigue Test AASHTO Designat
3、ion: TP 107-181Technical Section: 2d, Bituminous Materials Release: Group 3 (August) 1. SCOPE 1.1. This test method covers procedures for preparing and testing asphalt concrete mixtures to determine the damage characteristic curve and failure criterion via direct tension cyclic fatigue tests in the
4、Asphalt Mixture Performance Tester (AMPT). 1.2. This standard is applicable to laboratory prepared specimens of mixtures with nominal maximum size aggregate less than or equal to 25.0 mm (0.98 in.). Mixtures with a nominal maximum aggregate size greater than or equal to 25.0 mm (0.98 in.) may experi
5、ence lower success rates. 1.3. This standard may involve hazardous material, operations, and equipment. This standard does not purport to address all safety problems associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practices a
6、nd to 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) R 38, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) R 62, Developing Dynam
7、ic Modulus Master Curves for Asphalt Mixtures R 84, Developing Dynamic Modulus Master Curves for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT) T 342, Determining Dynamic Modulus of Hot Mix Asphalt (HMA) T 378, Determining the Dynamic Modulus and Flow Number for Asphalt Mixture
8、s Using the Asphalt Mixture Performance Tester (AMPT) 2.2. ASTM Standard: E4, Standard Practices for Force Verification of Testing Machines 2.3. Other Documents: 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applica
9、ble law.TS-2d TP 107-2 AASHTO FHWA Report, Development of Asphalt Mixture Performance Related Specifications, Final Report of Project DTFH61-08-H-00005, In Press, 2017. NCHRP Report 629, Equipment Specifications for the Simple Performance Test System, Appendix E, October 16, 2007. 3. TERMINOLOGY 3.1
10、. alpha term ()value corresponding to the maximum slope of the relaxation modulus master curve which is used in the accumulation of damage with time. 3.2. average rate of dissipated pseudo strain energy per cycle (GR)parameter used in the failure criterion for fatigue performance which is generated
11、from a pseudo strain energy density function relating pseudo strain and damage. 3.3. complex modulus (E*)a complex number that defines the relationship between stress and strain for a linear viscoelastic material. 3.4. cyclic pseudo secant modulus (C*)the secant modulus in stresspseudo strain space
12、for a single cycle. This pseudo modulus differs from C because it is computed using a steady-state assumption and is used only with cycle-based data. 3.5. damage (S)the internal state variable that quantifies microstructural changes in asphalt concrete. 3.6. damage characteristic curve (C versus S c
13、urve)the curve formed when plotting the damage on the x-axis and the pseudo secant modulus on the y-axis. It defines the unique relationship between the structural integrity and amount of damage in a given mixture. 3.7. dynamic modulus (|E*|)the norm of the E*, which is calculated by dividing the pe
14、ak-to-peak stress by the peak-to-peak axial strain measured during the steady-state period. 3.8. dynamic modulus ratio (DMR)the ratio between the dynamic modulus fingerprint and the dynamic modulus value from a master curve construction, both evaluated at the same temperature and frequency condition
15、. This value is also used to characterize specimen-to-specimen variability. 3.9. failure cycle (Nf)the cycle in which the measured phase angle drops sharply after a stable increase during cyclic loading. 3.10. fatigue analysis coefficients (K1, K2, K3)fitting coefficients to describe the classical s
16、tress (or strain) versus cycles to failure relationship. 3.11. phase angle ()the angle, expressed in degrees, between an applied sinusoidal stress and the resulting sinusoidal strain measured during the steady-state period. 3.12. pseudo strain (R)a quantity that is similar to strain but does not inc
17、lude time effects. Pseudo strain is calculated by solving the convolution integral of the strain and E(t). 3.13. pseudo secant modulus (C)the secant modulus in stresspseudo strain space. 3.14. relaxation modulus (E(t)the quotient of the stress response of a material with time to a constant step ampl
18、itude of strain. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d TP 107-3 AASHTO 4. SUMMARY OF METHOD 4.1. An actuator displacement-controlled and repeated cyclic loading is applied to a cylindric
19、al asphalt concrete specimen until failure. The applied stress and on-specimen axial strain response are measured and used to calculate the necessary quantities. The relationship between the damage (S) and the pseudo secant modulus (C) is determined and expressed as the damage characteristic curve.
20、It is important to consider this document pertains to direct tension testing in an AMPT. Test procedures will differ if using other machinery and it is recommended more specialized procedures be developed for these loading machines. 5. SIGNIFICANCE AND USE 5.1. The damage characteristic curve repres
21、ents the fundamental relationship between damage and material integrity for asphalt concrete mixtures. This property is independent of temperature, frequency, and mode of loading. Combined with the linear viscoelastic properties of asphalt concrete, the damage characteristic curve can be used to ana
22、lyze the fatigue characteristics of asphalt concrete mixtures. 5.2. Damage characteristic curves can also be combined with the failure criterion and additional pavement response models to predict the fatigue behavior of in-service asphalt concrete mixtures. 6. APPARATUS 6.1. Asphalt Mixture Performa
23、nce TesterAn AMPT or system meeting or exceeding the requirements of Equipment Specifications for the Simple Performance Test System, NCHRP Report 629, Appendix E, with the additional capability to conduct direct tension testing, as shown in Figure 1. The minimum requirements of the accuracy and res
24、olution of the equipment measurement system are summarized in Table 1. Figure 1General Schematic of Direct Tension Test Setup 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d TP 107-4 AASHTO Table
25、1Accuracy and Resolution of Equipment Measurement System Measurement Range Accuracy Resolution Load 0.12 to 13.5 kN (27.0 to 3034.9 lb) Error 1.0% 0.0012 kN (0.2698 lb) Machine deformation At least 12 mm (0.47 in.) Error 0.03 mm (0.001 in.) 0.0025 mm (9.843E-5 in.) On-specimen deformation Not specif
26、iedaError 1.0% Not specifiedbaA range of about 7000 is recommended. bA resolution less than 7.5 is recommended. 6.2. External Conditioning Chamber (optional)An environmental chamber for conditioning the test specimens to the desired testing temperature. The chamber shall be capable of controlling th
27、e temperature of the specimen over a temperature range of 5 to 25C (41 To 77F) to within 0.5C (1F). The chamber shall be large enough to accommodate at least a single test specimen and a “dummy” specimen with a thermocouple or other calibrated temperature-measuring devices mounted at the center for
28、temperature verification. 6.3. Axial Deformation Measurement SystemAxial deformations shall be measured in the middle 70 mm (2.76 in.) of the specimen using sensors mounted between gauge points that are glued to the specimen, an example of which is shown in Figure 2. The deformations shall be measur
29、ed at three locations 120 degrees apart, or four locations 90 degrees apart. Note 1If gauge-head type (spring-loaded) linear variable differential transducers (LVDTs) are chosen, care should be taken to ensure that the spring force is not so strong (less than 1 N or 0.22 lb) as to force the gauge po
30、ints apart. This effect can be measured by monitoring the deformation of a specimen that is lying on its side and is conditioned to the appropriate temperature measured using a spring-loaded LVDT that has been attached to the specimen. Note 2The reliability of sensors should be verified with the sup
31、plier or manufacturer. Figure 2General Schematic of Gauge Points (Not to Scale) 6.4. Loading PlatensAre required above and below the specimen to transfer the load from the testing machine to the specimen. The diameter of the loading platens shall be not less than 100 mm (3.94 in.) and not greater th
32、an 105 mm (4.13 in.). It is recommended that the diameter of platens is closer to the target specimen diameter of 100 mm (3.94 in.), as this improves centering of the specimen. Generally, these platens should be made of hardened or plated steel, or anodized high strength aluminum. Softer materials w
33、ill require more frequent replacement. Materials that have linear elastic modulus properties and hardness properties lower than that of 6061-T6 aluminum shall not be used. The face of each load platen shall be grooved to provide better adhesion between the glue and plate. The top loading platen shal
34、l be designed so that it can be mated to the test machine without inducing loading eccentricity. For machines using a three-point attachment 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d TP 107-
35、5 AASHTO configuration, the platens should simply be tightened into the machine using screws and a torque wrench. Note 3Users may also place a ball bearing between the platens and the top loading platform in an attempt to account for loading eccentricity. Extra care should be taken using the ball be
36、aring since it could have a negative effect if screws are overtightened. Note 4It is recommended the grooves in the end plates be approximately 0.6 mm (0.024 in.) deep and spaced laterally by a distance of approximately 1.9 mm (0.075 in.). The grooving pattern can be either concentric circles or a s
37、piral pattern. A V-shaped groove or a cross-hatched groove is suggested. The 60-degree point threading bit has been used successfully for making the grooves. 6.5. End Plate Gluing ApparatusShould be available for gluing the end plates to the asphalt concrete specimen. The device should ensure that t
38、he end plates and specimen are all centered, that the two platens are held parallel, and that the specimen is standing perpendicular to the plates. The weight resting on the specimen during curing of the adhesive shall not exceed 0.045 kN (10 lb), otherwise it shall be possible to clamp or otherwise
39、 hold the gluing apparatus at a fixed height for a period of at least 4 h. Figure 3 shows a gluing jig that has been used successfully. If no jig is available, the specimen can be glued directly in the test machine. To do this, the gluing should be performed with the machine in load control. The app
40、lied compressive load should not be greater than 0.045 kN (10 lb). Figure 3End Plate Gluing Apparatus 7. HAZARDS 7.1. Standard laboratory safety precautions must be observed when preparing and testing asphalt concrete specimens. 2018 by the American Association of State Highway and Transportation Of
41、ficials. All rights reserved. Duplication is a violation of applicable law.TS-2d TP 107-6 AASHTO 8. TESTING EQUIPMENT CALIBRATION 8.1. The guidelines provided in T 378 shall be followed to ensure that the test equipment and on-specimen measurement devices are properly calibrated. 8.2. If any of the
42、verifications yield data that do not comply with the accuracy specified, the problem shall be corrected prior to further testing. 8.3. The hydraulic machine shall be properly tuned in displacement control mode, to enable use of the strain selection guidance in this standard. In displacement control
43、mode, the tuning shall be such that there is a sinusoidal actuator deformation shape and the actuator displacement returns close to the initial position on the first cycle, as this will ensure the cycles are uniform and the input strain closely matches the output strain. If the machine is not tuned
44、properly, the strain selection guidance may need to be adjusted for the specific machine. 9. TEST SPECIMENS 9.1. Direct tension testing shall be performed on test specimens cored and cut from larger Superpave gyratory compacted specimens, prepared in accordance with R 83, with the exception of the a
45、llowance for 130-mm-height specimens. Meeting the height requirements for both the gyratory compacted specimens (from R 83, 180 mm) and final test specimens will minimize unwanted end failure of the test specimen due to an uneven air void distribution. The average height of the test specimens shall
46、be between 127.5 and 132.5 mm (5.0 and 5.2 in.), respectively. R 83 Note 5The specimen height that should be used and the cutting scheme will depend on the air void gradient produced by the specific compactor and the capabilities of the sawing equipment. For specimens compacted to a height of 180 mm
47、 (7.1 in.), it has been found that 25 mm (0.98 in.) should first be cut from the bottom face of the specimen (the face which was at the bottom of the gyratory compaction mold). Then, the remaining length should be cut so that the final specimen height is between 127.5 and 132.5 mm (5.0 and 5.2 in.).
48、 9.2. AgingLaboratory-prepared mixtures shall be temperature-conditioned in accordance with the 4-h, short-term oven-conditioning procedure outlined in R 30. Field mixtures need not be aged prior to testing. 9.3. Prepare at least three test specimens at the target air void content 0.5 percent. Depen
49、ding on mixture characteristics and operator experience, additional specimens may be necessary. For pavement performance analysis, it is strongly recommended to perform four successful tests to improve accuracy. 9.4. ReplicatesOne specimen should be tested at each input condition. 9.5. Specimen storageStore the test specimen, until tested, on its end on a flat shelf in a room with the temperature controlled between 15 and 27C (59.0 to 80.6F). Note 6Definitive research concerning the effects of test specimen
