1、Standard Method of Test for Rutting Resistance of Asphalt Mixtures Using Incremental Repeated Load Permanent Deformation (iRLPD) AASHTO Designation: TP 116-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2d TP 1
2、16-1 AASHTO Standard Method of Test for Rutting Resistance of Asphalt Mixtures Using Incremental Repeated Load Permanent Deformation (iRLPD) AASHTO Designation: TP 116-1511. SCOPE 1.1. This standard describes a test method for measuring the resistance of asphalt mixtures to rutting using Minimum Str
3、ain Rates (MSR) from an incremental Repeated Load Permanent Deformation (iRLPD) Test conducted by means of an Asphalt Mixture Performance Tester (AMPT) System. This practice is intended for dense- and gap-graded mixtures with nominal maximum aggregate sizes to 37.5 mm. 1.2. This standard may involve
4、 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 procedure to establish appropriate safety and health practices and to determine the applicability of regulatory
5、limitations prior to its use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: PP 60, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) R 30, Mixture Conditioning of Hot Mix Asphalt (HMA) 2.2. Other Publications: LTPPBind V 3.1, Developed by Pavement Sy
6、stems LLC (PaveSys) LTPPB Mohseni, A., and H. Azari. Effective Temperature for Permanent Deformation Testing of Asphalt Mixtures. In ISAP 2014. International Society for Asphalt Pavements, Lino Lakes, MN, 2014. Equipment Specification for the Simple Performance Test System, Version 3.0. Prepared for
7、 National Cooperative Highway Research Program (NCHRP), October 16, 2007. Azari, H., and M. Mohseni. Incremental Repeated Load Permanent Deformation Testing of Asphalt Mixtures. TRB No. 12-4381. Transportation Research Board, Washington, DC, 2012. Azari, H., and M. Mohseni. Permanent Deformation Cha
8、racterization of Asphalt Mixtures using Incremental Repeated Load Testing. In Asphalt Materials and Mixtures, Volume 4. Transportation Research Board, Washington, DC, 2013. Azari, H., and M. Mohseni. Effect of Short-Term Conditioning and Long-Term Aging on Permanent Deformation Characteristics of As
9、phalt Mixtures. In AAPT Journal, Volume 82. Association of Asphalt Pavement Technologists, Lino Lakes, MN, 2013. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 116-2 AASHTO 3. TERMINOLOGY 3.1.
10、Definitions: 3.1.1. confining pressurestress applied to all surfaces in a confined test. 3.1.2. deviator stressdifference between the total axial stress and the confining pressure in a confined test. 3.1.3. contact stressthe constant axial stress applied to hold the specimen in place. 3.1.4. loading
11、 increment500 cycles of a repeated load. 3.1.5. minimum strain rate (MSR)the lowest permanent strain per cycle in a loading increment, which is the strain rate due to the 500th cycle in the secondary stage. 3.1.6. permanent deformationnon-recovered deformation in a repeated load test. 3.1.7. repeate
12、d load cycleloading of 0.1 second followed by 0.9-second rest period. 3.1.8. strain ratethe permanent axial strain due to one repeated load cycle. 3.1.9. strain accelerationthe rate of change of the strain rate. 3.1.10. secondary loading stagethe loading cycle where the axial strain rate is stable.
13、4. SUMMARY OF THE TEST METHOD 4.1. This test method describes procedures for evaluating resistance of asphalt mixtures to rutting by measuring the Minimum Strain Rate (MSR) at various stress and temperature combinations using the iRLPD test. 4.2. The iRLPD test is conducted at one test temperature a
14、nd confining pressure in four 500-cycle increments. The deviator stress is held constant during each increment and is increased for each subsequent increment. The load pulse is 0.1 sec every 1.0 sec. Permanent axial strains due to each load cycle (permanent strain rate) are measured by the actuator.
15、 The minimum strain rate for each increment is defined as the permanent axial strain due to the last (500th) cycle. 5. SIGNIFICANCE AND USE 5.1. The Minimum Strain Rate (MSR) is the permanent deformation property of asphalt mixtures and represents the unit rutting damage due to a single heavy-axle l
16、oad at a specific temperature and tire pressure. MSR is used for mixture design verification, material characterization, and rutting performance evaluation. 5.2. This test method uses MSR as resistance of asphalt mixtures to permanent deformation instead of the flow number, which is used in TP 79. T
17、he flow number is the number of load cycles when asphalt mixture reaches flow. MSR is the permanent strain rate after 500 cycles, before flow is reached. While reaching flow is the condition for the flow number, the condition for the MSR is not reaching flow. 2015 by the American Association of Stat
18、e Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 116-3 AASHTO 6. APPARATUS 6.1. Specimen Fabrication EquipmentEquipment for fabricating iRLPD test specimens as described in PP 60. 6.2. Asphalt Mixture Performance Tester (AMPT)A dynamic
19、 test system meeting the requirements of the Equipment Specification for the Simple Performance Test System, Version 3.0. 6.3. Conditioning ChamberAn environmental chamber for conditioning the test specimens to the desired testing temperature. The environmental chamber shall be capable of controllin
20、g the temperature of the specimen over a temperature range from 40 to 70C (104 to 158F) to an accuracy of 0.5C (1F). 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 verificatio
21、n. 6.4. Latex Membranes100-mm (4-in.) diameter by 0.3 mm (0.012 in.) thick for use in confined tests. 7. HAZARDS 7.1. This test and associated standards involve handling of hot asphalt binder, aggregates, and asphalt mixtures. It also includes the use of sawing and coring machinery and servo-hydraul
22、ic testing equipment. Use standard safety precautions, equipment, and clothing when handling hot materials and operating machinery. 8. STANDARDIZATION 8.1. Items associated with this test that require calibration are included in the documents referenced in Section 2.2. Refer to the pertinent section
23、 of the referenced documents for information concerning calibration. 9. PROCEDURE 9.1. Test Specimen Preparation: 9.1.1. Testing shall be performed on 100-mm (4-in.) diameter by 150-mm (6-in.) tall test specimens fabricated in accordance with PP 60. Note 1Cylindrical test specimens of 100-mm diamete
24、r by 150-mm tall may be compacted to the size instead of being cut and cored from 150-mm diameter specimens using PP 60. For this purpose, T 312 procedure may be followed with the exception that 100-mm diameter SGC mold is used instead of a 150-mm mold. The SGC stress of 600 kPa at 30 gyrations per
25、minute may be utilized to compact the loose mixture to the proper height. The loose mixture weight should be adjusted for the 100-mm mold so that the desired air void is achieved. 9.1.2. Prepare at least three test specimens at the target air void content and aging condition. 9.1.3. The target air v
26、oid content should be selected based on the in-place density specification for the project. Note 2For typical in-place density specifications a target air void content of 7.0 percent and tolerance of 0.5 percent is reasonable. 2015 by the American Association of State Highway and Transportation Offi
27、cials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 116-4 AASHTO 9.1.4. Assemble each specimen to be tested with platens and membrane as follows. Place the specimen on the bottom platen. Stretch the membrane over the specimen and bottom loading platen. Install the lower
28、o-ring seal. Stretch the membrane over the top platen. Install the upper o-ring seal. 9.1.5. Encase the dummy specimen in a membrane. 9.1.6. Place the specimen and platen assembly in the environmental chamber with the dummy specimen, and monitor the temperature of the dummy specimen to determine whe
29、n testing can begin. 9.1.7. Turn on the Asphalt Mixture Performance Test (AMPT) System, set the temperature control to the desired testing temperature, and allow the testing chamber to equilibrate at the testing temperature for at least one hour. 9.1.8. When the dummy specimen and the testing chambe
30、r reach the target temperature, open the testing chamber, remove a test specimen and platen assembly, and quickly place it in the testing chamber. Note 3When confined tests are performed, the specimen must be vented to atmospheric pressure through the drainage lines. Properly connect the drainage li
31、nes to the loading platens, making sure that they are vented to atmospheric pressure through the bubble chamber in order to identify leaks. 9.1.9. Close the testing chamber and allow the chamber temperature to return to testing temperature. 9.1.10. Ensure that steps in Sections 9.1.8 and 9.1.9, incl
32、uding return of the test chamber to the target temperature, shall be completed within 5 minutes. 9.2. Test Temperature: 9.2.1. The test temperature is calculated from the Degree-Days (DD) parameter of the construction site using LTPPBind V3.1 software and the following equation: T = 58 + 7 DD 15 log
33、(H + 45) (1) where: T = Test Temperature, C; DD = Degree-Days 10C (1000) from LTPPBind V 3.1; and H = 0 for surface layer, depth to top of layer for base layer. Note 4When the location of the construction is not known, the most reasonable effective temperature for the region may be used. The effecti
34、ve temperatures in the United States generally vary between 50 and 60C. Therefore, the most reasonable test temperature for a moderate climate is 55C. However, 50C for a cold climate and 60C for a hot climate are more reasonable. 9.3. Test Description: 9.3.1. The test is conducted using one conditio
35、ning increment of 500 cycles and three consecutive test increments of increasing deviatoric stress for 500 cycles each. 9.3.2. The stress level for the conditioning increment is 200 kPa. 9.3.3. The stress levels for testing increments are 400, 600, and 800 kPa. 9.3.4. The contact stress for each inc
36、rement is 5 percent of the deviator stress. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 116-5 AASHTO 9.3.5. The confining pressure of 69 kPa is used throughout the test. 9.3.6. Follow the so
37、ftware prompts to begin the test. The Asphalt Mixture Performance Test System will automatically unload when the test is complete. 9.3.7. Upon completion of the test, open the test chamber, and remove the tested specimen. 9.3.8. Repeat steps in Sections 9.3.6 and 9.3.7 for the remaining test specime
38、ns. 10. CALCULATIONS 10.1. The minimum strain rate (MSR) for each test increment (400-, 600-, and 800-kPa stress) is determined from total permanent strain collected by the actuator. 10.2. Export the output data table into an Excel file. Compute the strain rate for each cycle by subtracting the tota
39、l strain for the cycle from the total strain of the previous cycle as follows: SRi= TSi TSi 1(2) where: i = Cycle Number, SRi= Strain Rate at the ith cycle, TSi= Total Permanent Strain at the ith cycle, and TSi 1= Total Permanent Strain at the cycle before the ith cycle. 10.3. Perform a linear regre
40、ssion using data for the last 50 cycles of the increment (cycles 451 to 500) with cycle number (i) as x-value and strain rate (SRi) as the y-value as follows, and determine the c and SA coefficients. SRi= c + SA i (3) where: c = model intercept, and SA = Strain Acceleration. Note 5The Strain Acceler
41、ation (SA) should always have negative value. If SA becomes a positive value for an increment, this is an indication that the test has reached tertiary flow and, thus, MSR may not be determined for that increment. 10.3.1. Determine the Minimum Strain Rate (MSR) for each loading increment, which is t
42、he estimated strain rate at 500th cycle as follows: Minimum Strain Rate (MSR) = c + SA 500 (4) 10.3.2. The graph of MSR versus Test Temperature (T) Deviator Stress (P) for three increments is called the MSR master curve. The equation is as follows: MSR = a(T P)b(5) where: 2015 by the American Associ
43、ation of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d TP 116-6 AASHTO T = Test temperature, C; P = Deviator stress, MPa; and a, b = Model coefficients. Note 6The MSR master curve explains the permanent deformation at any temperatu
44、re and stress level. The b coefficient may be estimated using the MSR at 600 kPa (MSR600) and assuming value of 0.001 for the “a” coefficient as follows: 6006000.0011000bTMSR=(6) ( )( )600log 1000log 0.6MSRbT=(7) Note 7The “b” coefficient is open ended but usually ranges between 2.0 and 3.0 and can
45、be used for ranking of mixtures. A b value of 2.0 is an indication of a very stiff material and a b value of 3.0 is an indication of a very soft material. 10.3.3. The allowable traffic level at a certain effective temperature may be determined from MSR at 600 kPa (MSR600) calculated from the test da
46、ta or the master curve. Use Equation 9 or Table 1 to determine the allowable traffic. log(ESAL) = 1.7 0.07 MSR600(8) ( )6001.7 0.0710MSRESAL= (9) where: ESAL = Allowable ESAL, millions; and MSR600= Minimum Strain Rate at 600 kPa and effective temperature. Table 1Maximum MSR Value by Traffic Level Tr
47、affic Level Design ESALs (million) Maximum MSR Value Light 1 24 Standard 1 to 3 17 Heavy 3 to 10 10 Very Heavy 10 to 30 3 Extreme 30 1 Note 8If the test is not conducted at the effective temperature of the site, then MSR for this temperature must be determined using the MSR master curve equation. 11
48、. REPORTING 11.1. Report the following: 11.1.1. Test temperature for each increment. 11.1.2. Average applied deviator stress for each test increment. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d
49、 TP 116-7 AASHTO 11.1.3. Average applied confining pressure. 11.1.4. Minimum Strain Rate (MSR) for each increment. 11.1.5. b power coefficient of the MSR master curve. 11.1.6. Estimated ESAL for the test temperature. 11.1.7. iRLPD software summary report for each specimen tested. 12. KEYWORDS 12.1. Asphalt mixture rutting test; incremental Repeated Load Permanent Deformation; iRLPD; Minimum Strain Rate; MSR. 1This provisional standard was first published in 2015. 2015 by the American A
