Ruggedness Testing of the Dynamic Modulus and Flow Number Tests with the Simple Performance Tester (2008)

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F1 A P P E N D I X F SPT Test Methods

F2 Proposed Standard Test Method for Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System NCHRP 9-29: PT 01 1. SCOPE 1.1 This standard describes test methods for measuring the dynamic modulus and flow number for hot-mix asphalt mixtures using the Simple Performance Test 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 hazardous materials, operations, and equipment, This standard does not purport to address all of the safety problems 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 limitations prior to its use. 2. REFERENCED DOCUMENTS 2.1 AASHTO Standards • NCHRP 9-29 PP 01, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor • NCHRP 9-29 PP 02, Developing Dynamic Modulus Master Curves for Hot-Mix Asphalt Concrete Using the Simple Performance Test System 2.2 Other Publications • Equipment Specification for the Simple Performance Test System, Version 3.0, Prepared for National Cooperative Highway Research Program (NCHRP), October 16, 2007. 3. TERMINOLOGY 3.1 Dynamic Modulus – |E* |, the absolute value of the complex modulus calculated by dividing the peak-to-peak stress by the peak-to-peak strain for a material subjected to a sinusoidal loading. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 1 of 14

F3 3.2 Phase Angle – δ , the angle in degrees between a sinusoidally applied stress and the resulting strain in a controlled-stress test. 3.3 Permanent Deformation – Non-recovered deformation in a repeated load test. 3.4 Confining Pressure - Stress applied to all surfaces in a confined test. 3.5 Deviator Stress - Difference between the total axial stress and the confining pressure in a confined test. 3.6 Flow Number. The number of load cycles corresponding to the minimum rate of change of permanent axial strain during a repeated load test. 4. SUMMARY OF THE TEST METHODS 4.1 This test method describes procedures for measuring the dynamic modulus and flow number for HMA. 4.2 In the dynamic modulus procedure an HMA specimen at a specific test temperature is subjected to controlled sinusoidal (haversine) 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 an HMA specimen at a specific test temperature is subjected to a repeated haversine axial compressive load pulse of 0.1 sec every 1.0 sec. 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 number 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 HMA for mechanistic-empirical pavement design. 5.2 The flow number is a property related to the resistance of HMA mixtures to permanent deformation. It can be used to evaluate mixtures and to design mixtures with specific resistance to permanent deformation. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 2 of 14

F4 6. APPARATUS 6.1 Specimen Fabrication Equipment - Equipment for fabricating dynamic modulus test specimens as described in NCHRP 9-29 PP 01, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor. 6.2 Dynamic Modulus Test System - A dynamic test system meeting the requirements of Equipment Specification for the Simple Performance Test System, Version 3.0. 6.3 Conditioning Chamber - An environmental chamber for conditioning the test specimens to the desired testing temperature. The environmental chamber shall be capable of controlling the temperature of the specimen over a temperature range from 4 to 60 ° C (39 to 140 ° F ) to an accuracy of ± 0.5 ° C (1 ° F). 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 verification. 6.4 Teflon Sheet - 0.25 mm (0.01 in) thick to be used as friction reducer between the specimen and the loading platens in the dynamic modulus test. 6.5 Latex Membranes – 100 mm (4 in) diameter by 0.3 mm (0.012 in) thick for use in confined tests and for manufacturing “greased double latex” friction reducers to be used between the specimen and the loading platens in the dynamic modulus and flow number tests. 6.6 Silicone Grease – Dow Corning Stopcock Grease or equivalent for manufacturing “greased double latex” friction reducers. 6.7 Balance – Balance capable of weighing to the nearest 0.01 g. The balance is used to weigh silicone grease 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 servo-hydraulic testing equipment. Use standard safety precautions, equipment, and clothing when handling hot materials and operating machinery. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 3 of 14

F5 9. PROCEDURE A - DYNAMIC MODULUS TEST 9.1 Test Specimen Fabrication 9.1.1 Testing shall be performed on 100 mm (4 in) diameter by 150 mm (6 in) high test specimens fabricated in accordance with NCHRP 9-29 PP 01, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor. 9.1.2 Prepare at least two test specimens to the target air void content and aging condition in accordance with NCHRP 9-29 PP 01, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor. Note 1 – A reasonable air void tolerance for test specimen fabrication is ± 0.5 %. Note 2 – The coefficient of variation for properly conducted dynamic modulus tests is approximately 13 %. The coefficient of variation of the mean dynamic modulus for tests on multiple specimens is given by Table 1. Table 1. Coefficient of Variation for the Mean of Dynamic Modulus Test on Replicate Specimens. Specimens Coefficient of Variation For the Mean, % 2 9.2 3 7.5 4 6.5 5 5.8 6 5.3 7 4.9 8 4.6 9 4.3 10 4.1 Use Table 1 to select an appropriate number of specimens based on the uncertainty that can be tolerated in the analysis. 8. STANDARDIZATION 8.1 Items associated with this practice that require calibration are included in the documents referenced in Section 2.2 Refer to the pertinent section of the referenced documents for information concerning calibration. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 4 of 14

F6 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 Teflon 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 (0.01 in) thick Teflon sheet cut to slightly larger than the loading platen. 9.3.2.2 “Greased double latex” friction reducers are fabricated from 0.3 mm (0.012 in) thick latex membranes as described in Appendix 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 friction reducers inside the testing chamber. Turn on the Simple Performance Test 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. 9.4.1.3 When the dummy specimen and the testing chamber reach the target temperature, open 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 reducer, and top loading platen. 9.4.1.5 Install the specimen mounted deformation measuring system on the gauge points per the manufacturer’s instructions. Ensure that the deformation measuring system is within its calibrated range. Make sure that the top loading platen is free to rotate during loading. 9.2 Test Specimen Instrumentation (Standard Glued Gauge Point System) 9.2.1 Attach the gauge points to the specimen in accordance with the manufacturer’s instructions. 9.2.2 Confirm that the gauge length is 70 mm (2.76 in) ± 1 mm (0.04 in) measured center to center of the gage points. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 5 of 14

F7 9.4.1.9 Follow the software prompts to begin the test. The Simple Performance Test System will automatically unload when the test is complete and display test data and data quality indicators. 9.4.1.10 Review the data quality indicators as discussed in Section 9.5 of this test procedure. Retest specimens with data quality indicators above the values specified in Section 9.5. 9.4.1.11 Once acceptable data have been collected, open the test chamber, and remove the tested specimen. 9.4.1.12 Repeat steps 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 platens and membrane as follows. Place the bottom friction 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. 9.4.2.2 Encase the dummy specimen in a membrane. 9.4.2.3 Place the specimen and platen assembly 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 Simple Performance Test 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. 9.4.1.6 Close the testing chamber and allow the chamber temperature to return to testing temperature. 9.4.1.7 Steps 9.4.1.3 through 9.4.1.6 including return of the test chamber to the target temperature shall be completed in 5 minutes. 9.4.1.8 Enter the required identification and control information into the Dynamic Modulus Software. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 6 of 14

F8 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 begin the test. The Simple Performance Test System will automatically unload when the test is complete and display test data and data quality indicators. 9.4.2.11 Review the data quality indicators as discussed in Section 9.5 of this test procedure. Retest specimens with data quality indicators above the values specified in Section 9.5. 9.4.2.12 Once acceptable data have been collected, open the test chamber, and remove the tested specimen. 9.4.2.13 Repeat steps 9.4.2.3 through 9.4.2.12 for the remaining test specimens. 9.5 Computations and Data Quality 9.5.1 The calculation of dynamic modulus, phase angle, and the data quality indicators is performed automatically by the Simple Performance Test System software. 9.5.2 Accept only test data meeting the data quality statistics given in Table 2. Table 3 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. 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. 9.4.2.6 Install the specimen mounted deformation measuring system outside the membrane on the gauge points per the manufacturer’s instructions. Ensure that the deformation measuring system is within its calibrated range. Make sure 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 testing temperature. 9.4.2.8 Steps 9.4.2.5 through 9.4.2.7 including return of the test chamber to the target temperature shall be completed in 5 minutes. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 7 of 14

F9 Table 3. Troubleshooting Guide for Data Quality Statistics. Item Cause Possible Solutions Deformation Drift not in direction of applied load. Gage points are moving apart. Reduce LVDT spring force. Add compensation springs. Reduce test temperature. Peak to Peak Strain too high. Load level too high. Reduce load level. Peak to Peak Strain too low. Load level too low. Increase load level. Load Standard Error > 10 %. Applied load not sinusoidal. Adjust tuning of hydraulics. Deformation Standard Error > 10 %. 1. Deformation not sinusoidal 2. Loose gage point. 3. Excessive noise on deformation signals. 4. Damaged LVDT. 1. Adjust tuning of hydraulics. 2. Check gage points. Reinstall if loose. 3. Check wiring of deformation sensors. 4. Replace LVDT. Deformation Uniformity > 30 %. 1. Eccentric loading. 2. Loose gage point. 3. Sample ends not parallel. 4. Poor gage point placement. 5. Non-uniform air void distribution. 1. Ensure specimen is properly aligned. 2. Check gage points. Reinstall if loose. 3. Check parallelism of sample ends. Mill ends if out of tolerance. 4. Check for specimen non-uniformity (segregation, air voids). Move gage points. 5. Ensure test specimens are cored from the middle of the gyratory specimen. Phase Uniformity > 3 degrees. 1. Eccentric loading. 2. Loose gage point. 3. Poor gage point placement. 4. Damaged LVDT. 1. Ensure specimen is properly aligned. 2. Check gage points. Reinstall if loose. 3. Check for specimen non-uniformity (segregation, air voids). Move gage points. 4. Replace LVDT. Table 2. Data Quality Statistics Requirements. Data Quality Statistic Limit Deformation Drift In direction of applied load Peak to Peak Strain 75 to 125 μstrain unconfined tests 85 to 115 μstrain confined tests Load standard error 10 % Deformation standard error 10 % Deformation uniformity 30 % Phase uniformity 3 degrees Note 3 – The data quality statistics in Table 2 are reported by the Simple Performance Test System software. If a dynamic modulus test system other than the Simple Performance Test System is used, refer to Equipment Specification for the Simple Performance Test System, Version 3.0 for algorithms for computation of dynamic modulus, phase angle, and data quality statistics. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 8 of 14

F10 10. PROCEDURE B – FLOW NUMBER TEST 10.1 Test Specimen Fabrication 10.1.1 Testing shall be performed on 100 mm (4 in) diameter by 150 mm (6 in) high test specimens fabricated in accordance with NCHRP 9-29 PP 01, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor. 10.1.2 Prepare at least three test specimens to the target air void content and aging condition in accordance with NCHRP 9-29 PP 01, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor. Note 4 – A reasonable air void tolerance for test specimen fabrication is ± 0.5 %. Note 5 – The coefficient of variation for the permanent deformation before flow in the flow number test is approximately 15 %. The coefficient of variation for the flow number is approximately 20 %. The coefficient of variation of the mean for tests on multiple specimens is given by Table 4. 10.2 Loading Platens and End Friction Reducers 10.2.1 For the flow number test, the top platen shall not be free to rotate. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 9 of 14 9.6 Reporting 9.6.1 For each specimen tested, report the following: 9.6.1.1 Test temperature. 9.6.1.2 Test frequency. 9.6.1.3 Confining stress level. 9.6.1.4 Dynamic modulus. 9.6.1.5 Phase angle. 9.6.1.6 Data quality statistics. 9.6.2 Attach Simple Performance Test System dynamic modulus test summary report for each specimen tested.

F11 10.3 Unconfined Tests 10.3.1 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. 10.3.2 Place platens and “greased double latex” friction reducers inside the testing chamber. Turn on the Simple Performance Test 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. 10.3.3 When the dummy specimen and the testing chamber reach the target temperature, open the testing chamber, remove a test specimen from the conditioning chamber, and quickly place it in the testing chamber. 10.3.4 Assemble each specimen to be tested with platens in the following order from bottom to top. Bottom loading platen, bottom “greased double latex” friction reducer, specimen, top “greased double latex” friction reducer, and top loading platen. 10.2.2 Prepare two “greased double latex” end friction reducers for each specimen that will be tested using the procedure specified in Appendix A. It is recommended that new friction reducers be used for each test. Table 4. Coefficient of Variation for the Mean of Properties From the Flow Number Test Coefficient of Variation for the Mean, % Specimens Permanent Deformation Before Flow Flow Number 2 10.6 14.1 3 8.7 11.5 4 7.5 10.0 5 6.7 8.9 6 6.1 8.2 7 5.7 7.6 8 5.3 7.1 9 5.0 6.7 10 4.7 6.3 Use Table 4 to select an appropriate number of specimens based on the uncertainty that can be tolerated in the analysis. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 10 of 14

F12 10.4.3 Place the specimen and platen assembly in the environmental chamber with the dummy specimen, and monitor the temperature of the dummy specimen to determine when testing can begin. 10.4.4 Turn on the Simple Performance Test 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. 10.4.5 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. 10.4.6 Close the testing chamber and allow the chamber temperature to return to testing temperature. Make sure that the top loading platen is not permitted to rotate during loading. 10.3.5 Close the testing chamber and allow the chamber temperature to return to testing temperature. Make sure that the top loading platen is not permitted to rotate during loading. 10.3.6 Steps 10.3.3 and 10.3.5 including return of the test chamber to the target temperature shall be completed in 5 minutes. 10.3.7 Enter the required identification and control information into the Flow Number Software. 10.3.8 Follow the software prompts to begin the test. The Simple Performance Test System will automatically unload when the test is complete. 10.3.9 Upon completion of the test, open the test chamber, and remove the tested specimen. 10.3.10 Repeat steps 10.3.4 through 10.3.9 for the remaining test specimens. 10.4 Confined Tests 10.4.1 Assemble each specimen to be tested with platens and membrane as follows. Place the bottom “greased double latex” friction 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 “greased double latex” friction reducer and top platen on top of the specimen, and stretch the membrane over the top platen. Install the upper o-ring seal. 10.4.2 Encase the dummy specimen in a membrane. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 11 of 14

F13 10.6.1.2 Average applied deviatoric stress. 10.6.1.3 Average applied confining stress. 10.6.2 Average and standard deviation of flow numbers for the specimens tested. 10.6.3 Average and standard deviation of the permanent strain at the load cycles of interest. 10.6.4 Attach Simple Performance Test System flow number test summary report for each specimen tested. 10.4.7 Steps 10.4.5 and 10.4.6 including return of the test chamber to the target temperature shall be completed in 5 minutes. 10.4.8 Enter the required identification and control information into the Flow Number Software. 10.4.9 Follow the software prompts to begin the test. The Simple Performance Test System will automatically unload when the test is complete. 10.4.10 Upon completion of the test, open the test chamber, and remove the tested specimen. 10.4.11 Repeat steps 10.4.5 through 10.4.10 for the remaining test specimens. 10.5 Calculations 10.5.1 The calculation of the permanent strain for each load cycle and the flow number for individual specimens is performed automatically by the Simple Performance Test System software. 10.5.2 Compute the average and standard deviation of the flow numbers for the replicate specimens tested. 10.5.3 Compute the average and standard deviation of the permanent strain at the load cycles of interest. 10.6 Reporting 10.6.1 Report the following: 10.6.1.1 Test temperature. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 12 of 14

F14 A3.2 Trace the circumference of the loading platen on the sheet of latex, then cut along the tracing to form circular latex sheets that are slightly larger than the loading platen. Four are needed to fabricate friction reducers for the top and bottom of the specimen. A3.3 Place one circular latex sheet on the balance and weigh 0.25 ± 0.5 g of silicone grease onto the middle of the latex sheet. A3.4 Spread the silicone grease evenly over the latex sheet by rubbing in a circular motion from the center to the outside of the sheet. A3.5 Place the second circular latex sheet on top of the silicone grease. 11. KEYWORDS 11.1 Dynamic modulus, phase angle, flow number, permanent deformation, repeated load testing. APPENDIX A. METHOD FOR PREPARING GREASED DOUBLE LATEX END FRICTION REDUCERS FOR THE FLOW NUMBER TEST (MANDATORY INFORMATION) A1. PURPOSE A1.1 This Appendix presents a procedure for fabricated “greased double latex” end friction reducers for the flow number test. A1.2 These end friction reducers are mandatory for the flow number test. A2. SUMMARY A2.1 “Greased double latex” end friction reducers are fabricated by cutting two circular latex sheets from a latex membrane used for confining specimens, applying a specified weight of silicone grease evenly over one of the latex sheets, then placing the second latex sheet over the first. A3. PROCEDURE A3.1 Cut a 0.3 mm (0.012 in) thick latex membrane along its long axis to obtain a rectangular sheet of latex. The sheet will be approximately 315 mm (12.5 in) by 250 mm (10 in). Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 13 of 14

F15 A3.6 If the friction reducer will be used in confined tests, cut or punch a hole through both latex sheets at the location of the vent in the loading platen. Determining the Dynamic Modulus and Flow Number for Hot Mix Asphalt (HMA) Using the Simple Performance Test System 14 of 14