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Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt (2010)

Chapter: Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods

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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
×
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Suggested Citation:"Appendix C - Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods." National Academies of Sciences, Engineering, and Medicine. 2010. Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt. Washington, DC: The National Academies Press. doi: 10.17226/14367.
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C-1 A P P E N D I X C Draft AASHTO Standard for Steady Shear Flow and Phase Angle Methods Note: These draft specifications have been modified for the purpose of inclusion in this report.

C-2 Standard Method of Test for Determining the Laboratory Mixing & Compaction Temperature of Asphalt Binder Using a Dynamic Shear Rheometer (DSR) Steady Shear Flow Method AASHTO Designation: X XXX-XX

C-3 Standard Method of Test for Determining the Laboratory Mixing & Compaction Temperature of Asphalt Binder Using a Dynamic Shear Rheometer (DSR) Steady Shear Flow Method AASHTO Designation: X XXX-XX SCOPE This test method covers the determination of laboratory mixing and compaction temperatures using a steady shear flow test. The steady shear flow test is conducted using the Dynamic Shear Rheometer (DSR) utilizing the rheometers capability to function in constant rotation in one direction. The values stated in SI units are to be regarded as the standard. This standard does not purport to address all of the safety concerns, if any, 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. REFERENCED DOCUMENTS 2.1 AASHTO Standards • M320, PERFORMANCE GRADED ASPHALT BINDER • T315, DETERMINING THE RHEOLOGICAL PROPERTIES OF ASPHALT BINDER USING A DYNAMIC SHEAR RHEOMETER (DSR) 2.2. ASTM Standard • D8, TERMINOLOGY RELATING TO MATERIALS FOR ROADS AND PAVEMENTS • D2493,VISCOSITY-TEMPERATURE CHART FOR ASPHALTS

C-4 3. TERMINOLOGY 3.1 Definitions: 3.1.1 Definitions of terms used in this practice may be found in ASTM D8, determined from common English usage, or combinations of both. 4. SUMMARY OF TEST METHOD 4.1. A sample of unaged asphalt binder is tested in the DSR using the 25-mm plate geometry with a 0.5-mm gap setting. The sample is tested in flow mode over a range of shear stresses from 0 to 500 Pa at 3 temperatures (76, 82, 88C). 4.2. After testing is completed, the viscosity values at 500 Pa are plotted versus temperature on a log-log scale. From the plot, mixing and compaction temperatures are determined based upon specified viscosity ranges. 5. SIGNIFICANCE AND USE 5.1 This test method is designed to determine the laboratory mixing and compaction temperatures for modified and unmodified asphalt binders. 6. PROCEDURE 6.1. Sample Preparation – The sample for the Steady Shear Flow test is prepared the same as samples for T 315 using the 25-mm plates with the following exceptions as noted in 6.1.1. The temperature control will also follow T 315 requirements. 6.1.1 The test gap for the Steady Shear Flow test will be 0.5 mm. An additional 0.025- mm gap will be added before trimming to allow for creation of the bulge. 6.2. Set the DSR software to perform a steady shear flow test from 50 to 500 Pa, collecting 5 data points for viscosity per log decade. 6.2.1 A 12 second data-sampling period should be used. 6.2.2 Steady state conditions will be met when 3 consecutive viscosity readings vary less than 2%. A maximum test time for each stress level of 12 minutes should be set to ensure that tests won’t last interminably.

C-5 6.3. After testing is completed, increase temperature by 6°C and repeat steps 6.1 – 6.3 until the number of desired test temperatures has been reached. 7. HAZARDS 7.1. Use standard laboratory safety procedures in handling the hot asphalt binder when preparing specimens for this test method. 8. CALCULATION 8.1. Using the results obtained in Section 6, create a log-log plot of Viscosity (Pa-S) at 500 Pa versus Temperature (°C). Information on the construction of viscosity – temperature charts can be found in ASTM D2493. 8.2. Construct a line through the 3 data points on the plot created in section 8.1. Extend the line as necessary to cross mixing and compaction target viscosity ranges. 8.3. Using target ranges of 0.15 to 0.19 Pa-S for mixing and 0.32 – 0.38 Pa-S for compaction, determine the mixing and compaction temperature ranges either visually or using a computer graphing program. 9. REPORT 9.1 Report the following information: 9.1.1 Sample identification; 9.1.2. Test Temperatures, nearest 0.1 °C; 9.1.3. Viscosity at 500 Pa for each test temperature, cP; 9.1.4. Mixing temperature range, nearest °C; 9.1.5. Compaction temperature range, nearest °C;

C-6 10. PRECISION AND BIAS 10.1. Precision – The research required to develop precision estimates has not been conducted. 10.2. Bias – The research required to establish the bias has not been conducted. 11. KEYWORDS 11.1. Steady Shear Flow; laboratory mixing temperature; laboratory compaction temperature, Dynamic Shear Rheometer (DSR); modified asphalt binder, target viscosity range. APPENDIX X.1. SAMPLE CALCULATIONS X1.1. Table X1.1 shows a set of test results at 3 temperatures: Table X1.1 – Steady Shear Flow Test Results Test Temperature, °C Viscosity at 500 Pa, Pa-S 34.176.0 18.882.0 10.788.0 X.1.2. Figure X1.1 shows the data in Table X1.1 plotted on a log-log Temperature - Viscosity chart:

C-7 Temperature, C V isc o sit y, Pa - s 0.1 1 10 52 58 88 100 150 165 180 200 Mixing Range Compaction Range 64 76 82 53102107 100 500 Figure X1.1 – Test Data Plot Showing Viscosity at 500 Pa and 3 Test Temperatures X.1.3 Using a compaction temperature range of 0.32 – 0.38 Pa-S, the laboratory compaction temperature of this asphalt binder will be 137 – 140°C. X.1.4. Using a mixing temperature range of 0.15 – 0.19 Pa-S, the laboratory mixing temperature of this asphalt binder will be 152 – 157°C.

C-8 Standard Method of Test for Determining the Laboratory Mixing & Compaction Temperature of Asphalt Binder Using a Dynamic Shear Rheometer (DSR). The Phase Angle Method. AASHTO Designation: X XXX-XX American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001

C-9 Standard Method of Test for Determining the Laboratory Mixing & Compaction Temperature of Asphalt Binder Using a Dynamic Shear Rheometer (DSR) The Phase Angle Method AASHTO Designation: X XXX-XX ________________________________________________ SCOPE This test method covers the determination of the dynamic shear modulus and phase angle of asphalt binder when tested in dynamic (oscillatory) shear using parallel plate test geometry. It is applicable to asphalt binders having dynamic shear modulus values in the range from 50 Pa to 10 MPa. This range in modulus is typically obtained between 40°C and 150°C at an angular frequency of 0.1 to 100 rad/s. This test method is intended for determining the linear viscoelastic properties of asphalt binders over a range of both frequency & temperature in order to determine a reasonable master curve of the visco-elastic properties of asphalt binder. This master curve will be used to determine the appropriate laboratory mixing & compaction temperatures. This standard is appropriate for unaged material or material aged in accordance with T 240 and R 28. Particulate material in the asphalt binder is limited to particles with longest dimensions less than 250µm. 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 use. ____________________________________________________________________

C-10 REFERENCED DOCUMENTS AASHTO Standards: • M 320, Performance-Graded Asphalt Binder • R 28, Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV) • R 29, Grading or Verifying the Performance Grade of an Asphalt Binder • T 40, Sampling Bituminous Materials • T 240, Effect of Heat and Air on a Moving Film of Asphalt (Rolling Thin-Film Oven Test) ASTM Standards: • C 670, Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials • E 1, Specification for ASTM Thermometers • E 77, Standard Test Method for Inspection and Verification of Thermometers • E 563, Standard Practice for Preparation and Use of an Ice-Point Bath as a Reference Temperature • E 644, Standard Test Methods for Testing Industrial Resistance Thermometers • D 2170, Standard Test Method for Kinematic Viscosity of Asphalts (Bitumens) • D 2171, Standard Test Method for Viscosity of Asphalts by Vacuum Capillary Viscometer Deutsche Industrie Norm (DIN) Standards: • 43760, Standard for Calibrations of Thermocouples National Cooperative Highway Research Program Report: • NCHRP Report xxx, Procedure for Determining Mixing and Compaction Temperatures of Asphalt Binders in Hot Mix Asphalt _______________________________________________________________________ TERMINOLOGY Definitions: asphalt binder—an asphalt-based cement that is produced from petroleum residue either with or without the addition of non-particulate organic modifiers.

C-11 Descriptions of Terms Specific to This Standard: annealing—heating the binder until it is sufficiently fluid to remove the effects of steric hardening. complex shear modulus (G*)—ratio calculated by dividing the absolute value of the peak-to-peak shear stress, τ, by the absolute value of the peak-to-peak shear strain, γ. calibration—process of checking the accuracy and precision of a device using NIST- traceable standards and making adjustments to the device where necessary to correct its operation or precision and accuracy. dummy test specimen—a specimen formed between the dynamic shear rheometer (DSR) test plates from asphalt binder or other polymer to measure the temperature of the asphalt binder held between the plates. The dummy test specimen is used solely to determine temperature corrections. loading cycle—a unit cycle of time for which the test sample is loaded at a selected frequency and stress or strain level. phase angle (δ)—the angle in radians between a sinusoidally applied strain and the resultant sinusoidal stress in a controlled-strain testing mode, or between the applied stress and the resultant strain in a controlled-stress testing mode. loss shear modulus (G´´)—the complex shear modulus multiplied by the sine of the phase angle expressed in degrees. It represents the component of the complex modulus that is a measure of the energy lost (dissipated during a loading cycle). storage shear modulus (G´)—the complex shear modulus multiplied by the cosine of the phase angle expressed in degrees. It represents the in-phase component of the complex modulus that is a measure of the energy stored during a loading cycle. parallel plate geometry—refers to a testing geometry in which the test sample is sandwiched between two relatively rigid parallel plates and subjected to oscillatory shear. oscillatory shear—refers to a type of loading in which a shear stress or shear strain is applied to a test sample in an oscillatory manner such that the shear stress or strain varies in amplitude about zero in a sinusoidal manner. linear viscoelastic—within the context of this specification refers to a region of behavior in which the dynamic shear modulus is independent of shear stress or strain.

C-12 portable thermometer—is an electronic device that consists of a temperature detector (probe containing a thermocouple or resistive element), required electronic circuitry, and readout system. reference thermometer—a NIST–traceable liquid-in-glass or electronic thermometer that is used as a laboratory standard. temperature correction—difference in temperature between the temperature indicated by the DSR and the test specimen as measured by the portable thermometer inserted between the test plates. thermal equilibrium—is reached when the temperature of the test specimen mounted between the test plates is constant with time. thermal gradient- temperature inequality throughout the test specimen due to the poor thermal conductivity of or poor stability of the temperature control device. These inequalities are typically from top of specimen to bottom of specimen and/or from center of specimen to edge of specimen. Thermal gradients can cause errors in the reporting of the specimen’s modulus & phase angle. thermal hysteresis- where the modulus of the specimen at temperature X differs depending on whether the specimen is heated to temperature X or cooled to reach temperature X. verification—process of checking the accuracy of a device or its components against an internal laboratory standard. It is usually performed within the operating laboratory. steric hardening—see molecular association. molecular association—a process where associations occur between asphalt binder molecules during storage at ambient temperature. Often called steric hardening in the asphalt literature, molecular associations can increase the dynamic shear modulus of asphalt binders. The amount of molecular association is asphalt specific and may be significant even after a few hours of storage. Isotherms – equation or curve on a graph representing he behavior of a material at a constant temperature Isochrones – equation or curve on a graph representing he behavior of a material at a constant frequency Frequency Sweep – is an oscillatory test performed within the linear visco-elastic region of a sample where the variable is frequency and the temperature is held constant.

C-13 Master curve – when several frequency curves (isotherm) determined at different temperatures are shifted, each one according to its individual shift factor, to a reference temperature and presented together in one diagram afterwards, the result is the so-called master curve. Black space – is a graphic representation of phase angle variation with respect to complex modulus from isotherm done at different temperatures. _____________________________________________________________________ SUMMARY OF TEST METHOD This standard contains the procedure used to measure the complex shear modulus (G*) and phase angle () of asphalt binders using a dynamic shear rheometer and parallel plate test geometry. The standard is suitable for use when the dynamic shear modulus varies between 50 Pa and 10 MPa. This range in modulus is typically obtained between 40 and 150°C at an angular frequency range of 0.1 to 100 rad/s, dependent upon the grade, test temperature, and conditioning (aging) of the asphalt binder. Testing is required at multiple temperatures to acquire phase angle values between 87 degrees and 75 degrees. Generally, this can be obtained using 3 temperatures, although more can be used. The required temperatures to test the sample will depend on the Performance Grade (PG) of the binder. Lower PG binders will be tested at lower temperatures while higher PG binders will be tested at higher temperatures. All grades will be tested at 80°C. The chart in Table 1. below provides a guide to temperature selection. Table 44—Temperature testing schedule Test specimens 1 mm thick by 25 mm in diameter are formed between parallel metal plates. During testing, one of the parallel plates is oscillated with respect to the other at pre-selected frequencies and rotational deformation

C-14 amplitudes (strain control) (or torque amplitudes (stress control)). The required stress or strain amplitude depends upon the value of the complex shear modulus of the asphalt binder being tested. The required amplitudes have been selected to ensure that the measurements are within the region of linear behavior. The test specimen is maintained at the test temperature to within ± 0.1°C by positive heating and cooling of the upper and lower plates or by enclosing the upper and lower plates in a thermally controlled environment or test chamber. In either case, the sample must be immersed in a bath of either forced air or flowing water to provide heat transfer with minimal thermal gradients and eliminate the potential of thermal hysteresis. Oscillatory loading frequencies using this standard can range from 0.1 to 100 rad/s using a sinusoidal waveform. The complex modulus (G*) and phase angle () are calculated automatically as part of the operation of the rheometer using proprietary computer software supplied by the equipment manufacturer. 4.6. Results obtained from the testing must combined to create a master curve. This master curve will be compiled using the time-temperature- superposition principle with a reference temperature set to 80°C. Rheometer manufacturer’s as well as other 3rd party software modeling providers offer automated software to perform this function. _______________________________________________________________________ SIGNIFICANCE AND USE The mixing process of hot mix asphalt requires the binders to adequately coat the aggregate to a uniform film thickness. The asphalt binder exhibits differing mechanical (visco-elastic) properties at different temperatures. Knowing the binders visco-elastic properties enables the proper selection of temperature where these visco-elastic behaviors enable adequate mixing and coating of the aggregate. The compaction process of hot mix asphalt requires the binder to move under compaction in order to achieve the proper pavement density. Knowing the binders visco-elastic properties enables the proper selection of temperature where these visco-elastic behaviors enable proper compaction to occur. A series of frequency sweeps are performed by the rheometer at several temperatures in an automated fashion. The data collected is then automatically processed to produce a time-temperature-superposition master curve of the binder at the reference temperature of 80°C. From the master curve, the frequency where the binder transitions from viscous (newtonian) behavior to visco-elastic (non newtonian) behavior provides information relating to the required temperature needed to adequately mix

C-15 or compact the asphalt binder. The phase angle is used to identify the transition frequency where the phase angle equals 86 degrees. Through a simple mathematical algorithm, this value of frequency is processed to both a mixing & compaction temperature. _______________________________________________________________________ APPARATUS Dynamic Shear Rheometer (DSR) Test System—A dynamic shear rheometer test system consisting of parallel metal plates, an environmental chamber, a loading device, and a control and data acquisition system. Test Plates—Metal test plates made from stainless steel or aluminum with smooth ground surfaces. A set of 25.00 ± 0.05 mm in diameter (Figure 1). The base plate in some rheometers is a flat plate. A raised portion, a minimum of 1.50 mm high, with the same radius as the upper plate is required. The raised portion makes it easier to trim the specimen and may improve test repeatability. Note 1—To get correct data, the upper and lower plates should be concentric with each other. At present there is no suitable procedure for the user to check the concentricity except to visually observe whether or not the upper and lower plates are centered with respect to each other. The moveable plate should rotate without any observable horizontal or vertical wobble. This operation may be checked visually or with a dial gauge held in contact with the edge of the moveable plate while it is being rotated. There are two numbers that determine the running behavior of a measuring system: centricity (horizontal wobble) and runout (vertical wobble). Typically, wobble can be seen if it is greater than ± 0.02 mm. For a new system, a wobble of ± 0.01 mm is typical. If the wobble grows to more than ± 0.02 mm with use, it is recommended that the instrument be serviced by the manufacturer. Dimension 25-mm Nominal A 25 ± 0.05 mm B ≥ 1.50 mm Figure 1—Plate Dimensions

C-16 Environmental Chamber—A chamber for controlling the test temperature, by heating (in steps or ramps), or cooling (in steps or ramps), to maintain a constant specimen environment. The medium for heating and cooling the specimen in the environmental chamber shall not affect asphalt binder properties. The temperature in the chamber may be controlled by the circulation of fluid such as water, conditioned forced gas such as air or nitrogen, surrounding the sample. The environmental chamber and the temperature controller shall control the temperature of the specimen, including thermal gradients within the sample, to an accuracy of ± 0.1°C. The chamber shall completely enclose the top and the bottom plates to minimize thermal gradients. Note 2—A circulating bath unit separate from the DSR which pumps the bath fluid through the test chamber may be required if a fluid medium is used. Temperature Controller—A temperature controller capable of maintaining specimen temperatures within ± 0.1°C for test temperatures ranging from 40 to 100°C. In some cases with highly polymer modified asphalt binder will require temperatures up to 140°C. Internal Temperature Detector for the DSR—A platinum resistance thermometer (PRT) mounted within the environmental chamber as an integral part of the DSR and in close proximity to the fixed plate, and with a resolution of 0.1°C (see Note 3). This thermometer shall be used to control the temperature of the test specimen between the plates and shall provide a continuous readout of temperature during the mounting, conditioning, and testing of the specimen. Note 3—Platinum resistance thermometer (PRTDs) meeting DIN Standard 43760 (Class A) or equal are recommended for this purpose. The PRTD shall be calibrated as an integral unit with its respective meter or electronic circuitry. Loading Device—The loading device shall apply a sinusoidal oscillatory load to the specimen over a frequency range of 0.10 to 100.0 ± 1%. The loading device shall be capable of providing either a stress controlled or strain controlled load. If the load is strain controlled, the loading device shall apply a cyclic torque sufficient to cause an angular rotational strain accurate to within 100 μ rad of the strain specified. If the load is stress controlled, the loading device shall apply a cyclic torque accurate to within 10 μ N⋅m of the torque specified. Total system compliance at 100 N⋅m torque shall be less than 2 mrad/N⋅m. The manufacturer of the device shall provide a certificate certifying that the frequency, stress, and strain are controlled and measured with an accuracy of one percent or less in the range of this measurement. Control and Data Acquisition System—The control and data acquisition system shall provide a record of temperature, frequency, deflection angle, and torque. Devices used to measure these quantities shall meet the accuracy

C-17 requirements specified in Table 2. In addition, the system shall calculate and record the shear stress, shear strain, complex shear modulus (G*) and phase angle (δ). The system shall measure and record G*, in the range of 100 Pa to 10 MPa, to an accuracy of 1.0 percent or less and the phase angle, in the range of 0 to 90 degrees, to an accuracy of 0.1 degrees. Table 2—Control and Data Acquisition System Measurement Requirements egnaRroeulaVycaruccAmuminiMnoitcnuF 10.0erutarepmeT oC Resolution ± 0.1 oC Stability ± 0.1 oC Gradients throughout sample 40 to 150 oC Range egnaRces/dar001otycneuqerF 1% Resolution / Accuracy 0.1 degree Phase Angle Measurement Nn01euqroT m Resolution 10µ to 10mN m Range darµ1elgnanoitcelfeD Specimen Mold (Optional)—The overall dimensions of the silicone rubber mold for forming asphalt binder test specimens may vary but the thickness shall be greater than 5 mm. If the mold is a single sample mold, the following dimensions have been found suitable: For a 25-mm test plate with a 1-mm gap, a mold cavity approximately 18 mm in diameter and 2.0 mm deep. Specimen Trimmer—A specimen trimmer with a straight edge at least 4 mm wide. Wiping Material—Clean cloth, paper towels, cotton swabs, or other suitable material as required for wiping the plates. Cleaning Solvents—Mineral oil, citrus-based solvents, mineral spirits, toluene, or similar solvent as required for cleaning the plates. Acetone for removing solvent residue from the surfaces of the plates. Reference Thermometer—Either a NIST-traceable liquid-in-glass thermometer(s) or NIST–traceable electronic thermometer shall be maintained in the laboratory as a temperature standard. This temperature standard shall be used to verify the portable thermometer (Section 9.3). Liquid-in-Glass Thermometer—NIST-traceable liquid-in-glass thermometer(s) with a suitable range and subdivisions of 0.1°C. The thermometer(s) shall be a partial immersion thermometer(s) within an ice point and shall be calibrated in accordance with ASTM E 563. Optical Viewing Device (Optional)—An optical viewing device for use with liquid-in- glass thermometers that enhances readability and minimizes parallax when reading the liquid-in-glass reference thermometer. · ·

C-18 Electronic Thermometer—An electronic thermometer that incorporates a resistive detector (see Note 3) with an accuracy of ± 0.05°C and a resolution of 0.01°C. The electronic thermometer shall be calibrated at least once per year using a NIST–traceable reference standard in accordance with ASTM E 77. Portable Thermometer—A calibrated portable thermometer consisting of a resistive detector, associated electronic circuitry, and digital readout. The thickness of the detector shall be no greater than 2.0 mm such that it can be inserted between the test plates. The reference thermometer (see Section 6.6) may be used for this purpose if its detector fits within the dummy specimen as required by Section 9.4.1 or 9.4.2. ________________________________________________________________________ HAZARDS Standard laboratory caution should be used in handling the hot asphalt binder when preparing test specimens. PREPARATION OF APPARATUS Prepare the apparatus for testing in accordance with the manufacturer’s recommendations. Specific requirements will vary for different DSR models and manufacturers. Inspect the surfaces of the test plates and discard any plates with jagged or rounded edges or deep scratches. Clean any asphalt binder residue from the plates with an organic solvent such as mineral oil, mineral spirits, a citrus-based solvent, or toluene. Remove any remaining solvent residue by wiping the surface of the plates with a cotton swab or a soft cloth dampened with acetone. If necessary, use a dry cotton swab or soft cloth to ensure that no moisture condenses on the plates. Mount the cleaned and inspected test plates on the test fixtures and tighten firmly. Select the testing temperature according to the grade of the asphalt binder or according to the preselected testing schedule (see Note 4). Allow the DSR to reach a stabilized temperature within ± 0.1°C of the test temperature. Note 4—M 320 and R 29 provide guidance on the selection of test temperatures. With the test plates at the test temperature or the middle of the expected testing range, establish the zero gap level (1) by manually spinning the moveable plate, and while the moveable plate is spinning, close the gap until the removable plate touches the fixed plate (The zero gap is reached when the plate stops spinning completely.), or, (2) for rheometers with normal force transducers, by closing the gap and observing the normal force and after

C-19 establishing contact between the plates, setting the zero gap at approximately zero normal force. Note 5—The frame, detectors, and fixtures in the DSR can change dimension with temperature causing the zero gap to change with changes in temperature. Adjustments in the gap are not necessary when measurements are made over a limited range of temperatures. The gap should be set at the test temperature or, when tests are to be conducted over a range of temperatures, the gap should be set at the middle of the expected range of test temperatures. If the instrument has thermal gap compensation, the gap may be set at the first test temperature instead of the middle of the range of test temperatures. Follow manufacturer’s recommendations for specific instrument model procedures to ensure accurate from testing over a range of temperatures. Once the zero gap is established as per Section 8.5, move the plates apart to approximately the test gap and preheat the plates. Preheating the plates promotes adhesion between the asphalt binder and the plates, especially at the intermediate grading temperatures. To preheat 25-mm plates, bring the test plates to the test temperature or the lowest test temperature if testing is to be conducted at more than one temperature. Move the plates apart and establish a gap setting of 1.05 mm for the 25-mm diameter test specimens. Note 6—In order to obtain adequate adhesion between the asphalt binder and the test plates, the plates must be preheated. Preheating is especially critical when the silicone mold is used to prepare the asphalt binder for transfer to the test plates. When the direct placement method is used, as long as the test plates are immediately brought in contact with the asphalt binder, the heat carried with the asphalt binder improves adhesion. The preheating temperature needed for proper adhesion will depend on the grade and nature of the asphalt binder and the test. For highly modified asphalt binders only, higher preheat temperatures may be used. ____________________________________________________________________________ VERIFICATION AND CALIBRATION Verify the DSR and its components at least every six months and when the DSR or plates are newly installed, when the DSR is moved to a new location, or when the accuracy of the DSR or any of its components is suspect. Four items require verification—test plate diameter, DSR torque transducer, portable thermometer, and DSR test specimen temperature. Verify the DSR temperature transducer before verifying the torque transducer. Verification of Plate Diameter—Measure the diameters to the nearest 0.01 mm. Maintain a log of the measured diameters as part of the laboratory quality control plan so that the measurements are clearly identified with specific plates. If the plates are not within tolerance, they must not be used.

C-20 Note 7—An error of ± 0.05 mm in the diameter of the plate results in a 0.8 percent error in the complex modulus for the 25-mm plate. For the 8-mm plate, errors in diameter of ± 0.01, ± 0.02, and ± 0.05 mm give respective errors in complex modulus of 0.5, 1.0, and 2.5 percent. Figure 2—Effect of Error in Gap or Plate Diameter Verification of Portable Thermometer—Verify the portable thermometer (used to measure the temperature between the test plates), using the laboratory reference thermometer. If the reference thermometer (Section 6.6) is also used as a portable thermometer to measure the temperature between the test plates, it shall be meet the requirements of Section 6.7. Electronic thermometers shall be verified using the same meters and circuitry (wiring) that are used when temperature measurements are made between the plates. Recommended Verification Procedure— Bring the reference thermometer into intimate contact with the detector from the portable thermometer and place them in a thermostatically controlled and stirred water bath (Note 8). Ensure that de- ionized water is used to prevent electrical conduction from occurring between electrodes of the resistive temperature sensitive element. If de-ionized water is not available, encase the reference thermometer and the detector of the portable thermometer into a waterproof plastic bag prior to placement into the bath. Obtain measurements at intervals of approximately 6°C over the range of test temperatures allowing the bath to come to thermal equilibrium at each temperature. If the readings of the portable thermometer and the reference thermometer differ by 0.1°C or more, record the difference at each temperature as a temperature correction, and maintain the corrections in a log as part of the laboratory quality control program.

C-21 Note 8—A recommended procedure for the high temperature range is to use a stirred water bath that is controlled to ± 0.1°C such as the viscosity bath used for ASTM D 2170 or D 2171. For a low temperature bath, an ice bath or controlled temperature bath may be used. Bring the probe from the portable thermometer into contact with the reference thermometer, and hold the assembly in intimate contact. A rubber band works well for this purpose. Immerse the assembly in the water bath, and bring the water bath to thermal equilibrium. Record the temperature on each device when thermal equilibrium is reached. Note 9—If the readings from the two devices differ by 0.5°C or more, the calibration or operation of the portable thermometer may be suspect, and it may need to be recalibrated or replaced. A continuing change in the temperature corrections with time may also make the portable thermometer suspect. Test Specimen Temperature Correction—Thermal gradients within the rheometer can cause differences between the temperature of the test specimen and the temperature indicated by the DSR thermometer (also used to control the temperature of the DSR). The DSR thermometer shall be checked at an interval no greater than six months. When these differences are 0.1°C or greater, determine a temperature correction by using a thermal detector mounted in a silicone rubber wafer (Section 9.4.1) or by placing asphalt binder (dummy sample) between the plates and inserting the detector of the portable thermometer into the asphalt binder (Section 9.4.2). Method Using Silicone Rubber Wafer—Place the wafer between the 25-mm test plates, and close the gap to bring the wafer into contact with the upper and lower plate so that the silicone rubber makes complete contact with the surfaces of the upper and lower plates. If needed, apply a thin layer of petroleum grease or anti-seize compound to completely fill any void space between the silicone rubber and the plates. Complete contact is needed to ensure proper heat transfer across the plates and silicone rubber wafer. Determine any needed temperature correction as per Section 9.4.3. Note 10—Anti-seize compound available by that name at hardware and auto supply stores is much less apt to contaminate the circulating water than petroleum grease. Note 11—The currently available silicone wafer is 2 mm thick and slightly greater than 25 mm in diameter. Method Using Dummy Test Specimen—The dummy test specimen shall be formed from asphalt binder or other polymer that can be readily formed between the plates. Mount the dummy test specimen between the test plates, and insert the detector (probe) of the portable thermometer into the dummy test specimen. Close the gap to the test gap (1 mm for 25-mm plates and 2 mm for 8-mm plates) keeping the detector centered vertically and radially in the dummy test specimen. Heat the plates as needed to allow the dummy test specimen to completely fill the gap between the test plates. It is not necessary to trim the dummy test specimen but avoid excessive material around the edges of the plates. Determine any needed temperature correction as per Section 9.4.3.

C-22 Note 12—Silly putty can leave a residue of silicone oil on the surfaces of the plates, and for this reason, its use as a dummy specimen is not recommended. Determination of Temperature Correction—Obtain simultaneous temperature measurements with the DSR thermometer and the portable thermometer at 6°C increments to cover the range of test temperatures. At each temperature increment, after thermal equilibrium has been reached, record the temperature indicated by the portable thermometer and the DSR thermometer to the nearest 0.1°C. Temperature equilibrium is reached when the temperature indicated by both the DSR thermometer and the portable thermometer do not vary by more than 0.1°C over a five minute time period. Obtain additional measurements to include the entire temperature range that will be used for measuring the dynamic shear modulus. Plot Correction versus Specimen Temperature—Using the data obtained in Section 9.4, prepare a plot of the difference between the two temperature measurements versus the temperature measured with the portable thermometer (see Figure 3). This difference is the temperature correction that must be applied to the DSR temperature controller to obtain the desired temperature in the test specimen between the test plates. Report the temperature correction at the respective test temperature from the plot and report the test temperature between the plates as the test temperature. Alternatively, the instrument software may provide these temperature corrections automatically. Note 13—The difference between the two temperature measurements may not be a constant for a given rheometer but may vary with differences between the test temperature and the ambient laboratory temperature as well as with fluctuations in ambient temperature. The difference between the two temperature measurements is caused in part by thermal gradients in the test specimen and fixtures. Figure 3—Determination of Temperature Correction

C-23 Verification of DSR—Verify the accuracy of the torque transducer and angular displacement transducer. Note 14—A newly installed or reconditioned instrument should be verified on a weekly basis using the procedures in Section 9.5 until acceptable verification has been demonstrated. Maintaining the data in the form of a control chart where the verification measurements are plotted versus calendar date is recommended (see Appendix X2). Verification of Torque Transducer—Verify the calibration of the torque transducer a minimum of once every six months using a reference fluid or manufacturer-supplied fixtures when the calibration of the torque transducer is suspect or when the dynamic viscosity, as measured for the reference fluid, indicates that the torque transducer is not in calibration. Verification of Torque Transducer with Reference Fluid—The complex viscosity measured with the DSR shall be within three percent of the capillary viscosity as reported by the manufacturer of the reference fluid; otherwise, the calibration of the torque transducer shall be considered suspect. Compare the fluid reported viscosity to the instrument reported complex viscosity (η*). Alternately, calculate the complex viscosity from the complex modulus (G*) divided by the angular frequency in rad/s. Recommended practice for using the reference fluid is given in Appendix X3. Note 15—A suitable reference fluid is available from Cannon Instrument Company as Viscosity Standard Number N2700000SP. Verification of Torque Transducer with Fixtures—Verify the calibration of the torque transducer using the manufacturer-supplied fixtures in accordance with the instructions supplied by the manufacturer. Suitable manufacturer-supplied fixtures are not widely available. If suitable fixtures are not available, this requirement shall be waived. Verification of Angular Displacement Transducer—If manufacturer-supplied fixtures are available, verify the calibration every six months or when the calibration of the DSR is suspect. If suitable fixtures are not available, this requirement shall be waived. If the DSR cannot be successfully verified as per Section 9.5, it shall not be used for testing in accordance with this standard until it has been successfully calibrated by the manufacturer or other qualified service personnel. ______________________________________________________________________ PREPARING SAMPLES AND TEST SPECIMENS Preparing Test Samples—If unaged binder is to be tested, obtain test samples according to T 40. Anneal the asphalt binder from which the test specimen is obtained by heating until sufficiently fluid to pour the required specimens. Annealing prior to testing

C-24 removes reversible molecular associations (steric hardening) that occur during normal storage at ambient temperature. Do not heat the binder above a temperature of 163°C. Cover the sample, and stir it occasionally during the heating process to ensure homogeneity and to remove air bubbles. Minimize the heating temperature and time to avoid hardening the sample. Note 16—For neat asphalt binders, minimum pouring temperatures that produce a consistency equivalent to that of SAE 10W30 motor oil (readily pours but not overly fluid) at room temperature are recommended. Heating unaged asphalt to temperatures above 135°C should be avoided; however, with some modified asphalts or heavily aged binders, pouring temperatures above 135°C may be required. Cold material from storage containers must be annealed prior to usage. Structure developed during storage can result in overestimating the modulus by as much as 50 percent. Preparing asphalt binderTest Specimens—Zero the gap as specified in Section 8. Carefully clean and dry the surfaces of the test plates so that the specimen will adhere to both plates uniformly and strongly. Bring the chamber to the starting test temperature or the beginning of the range (see Note 6) when using 25-mm specimens. This requirement is to preheat the upper and lower plates to allow specimen adhesion to both plates. Prepare a test specimen using one of the methods specified in Section 10.3.1, 10.3.2, or 10.3.3. Transfer asphalt binder to one of the test plates through pouring (Section 10.3.1), direct transfer (Section 10.3.2), or by use of a silicone mold (Section 10.3.3). Note 18—Direct transfer or pouring are the preferred methods because the test results are less likely to be influenced by steric hardening than with the silicone mold method. Direct placement and direct pouring result in higher asphalt binder temperatures when the plates and asphalt binder are brought into contact, improving adhesion. For this reason, it is also important to bring the asphalt binder and plates into contact promptly after pouring or direct placement. Pouring—Only when using rheometers that are designed for removal of the plates without affecting the zero setting, remove the removable plate and, while holding the sample container approximately 15 mm above the test plate surface, pour the asphalt binder at the center of the upper test plate continuously until it covers the entire plate except for an approximate 2-mm wide strip at the perimeter (see Note 19). Wait only long enough for the specimen to stiffen, to prevent movement, and then mount the test plate in the rheometer for testing. Note 19—An eye dropper or syringe may be used to transfer the hot asphalt binder to the plate. Direct Transfer—Transfer the hot binder to one of the plates using a glass or metal rod, spatula, or similar tool. Immediately after transferring the hot binder to one of the plates, proceed to Section 10.4 to trim the specimen and form the bulge. Note 20—A small, narrow stainless steel spatula of the type used to weigh powders on

C-25 an analytical balance has been found suitable for transferring the hot binder. When using a rod, form a mass of sufficient size to form the test specimen by using a twisting motion. The twisting motion seems to keep the mass on the rod in control. A 4- to 5-mm diameter rod is suitable. Silicone Mold—Pour the hot asphalt binder into a silicone rubber mold that will form a pellet having dimensions as required in Section 6.2. Allow the silicone rubber mold to cool to room temperature. The specimen may be mounted to either the upper or lower plate. To mount the specimen to the lower plate, remove the specimen from the mold and center the pellet on the lower plate of the DSR. To mount the specimen to the upper plate, center the specimen still in the silicone rubber mold, on the upper plate. Gently press the specimen to the upper plate and then carefully remove the silicone rubber mold leaving the specimen adhered to the upper plate. The filled mold should be cooled at room temperature by placing the mold on a flat laboratory bench surface without chilling. Cooling to below room temperature results in an unknown thermal history that may affect the measured values of modulus and phase angle. Cooling may also result in the formation of moisture on the surface of the specimen that will interfere with adhesion of the specimen to the plates. Note 21—Solvents should not be used to clean the silicone rubber molds. Wipe the molds with a clean cloth to remove any asphalt binder residue. With use, the molds will become stained from the asphalt binder, making it difficult to remove the binder from the mold. If sticking becomes a problem, discard the mold. Note 22—Some binder grades cannot be removed from the silicone mold without cooling. Materials such as PG 52-34, PG 46-34, and some PG 58-34 grades do not lend themselves to being removed from the mold at ambient temperatures. If the binder specimen cannot be removed from the mold without cooling, the direct transfer or pouring method may be used, or the filled mold may be chilled in a freezer or refrigerator for the minimum time needed to facilitate demolding the specimen. Trimming Test Specimen—Immediately after the specimen has been placed on one of the test plates as described above, move the test plates together until the gap between the plates equals the testing gap plus the gap closure required to create the bulge. (See Section 10.5 for gap closure required to create the bulge.) Trim excess binder by moving a heated trimming tool around the edges of the plates so that the asphalt binder is flush with the outer diameter of the plates. Note 23—The trimming tool should be at a temperature that is sufficiently hot as to allow trimming but not excessively hot as to pyrolyse the edge of the specimen. Note 24—The gap should be set at the starting test temperature (Section 11.1.1) or at the middle of the expected range of test temperatures (Section 11.1.2). See Note 5 for guidance on setting the gap. Typically, reliable test results may be obtained with a single sample using temperatures within 12oC of the temperature at which the gap is set.

C-26 Creating Bulge—When the trimming is complete, decrease the gap by the amount required to form a slight bulge at the outside face of the test specimen. The gap required to create a bulge is rheometer specific and depends upon factors such as the design of the rheometer and the temperature difference between the trimming temperature and test temperature. Recommended closure values for creating the gap are 0.05 mm for the 25-mm plate. A recommended practice for verifying the gap closure required to produce an appropriate bulge is given in Appendix X4. Note 25—The complex modulus is calculated with the assumption that the specimen diameter is equal to the plate diameter. If the binder forms a concave surface at its outer edges this assumption will not be valid and the modulus will be underestimated. The calculated modulus is based upon the radius of the plate raised to the fourth power. A slight bulge equal to approximately one-quarter of the gap is recommended. A procedure for determining the closure required to form an acceptable gap is given in Appendix X4. ____________________________________________________________________________ PROCEDURE Program the DSR to perform a frequency sweep from 0.1 rad/sec to 100 rad/s, 10 points per decade logarithmically spaced, use a strain of 12% (or as needed to ensure all the testing is within the linear region for the sample tested). Testing should begin at the lowest frequency and increment up to the highest frequency. Program the DSR to perform the series of isotherms. Set the rheometer to perform the frequency sweep defined in 11.1 to be performed at multiple temperatures starting from the lowest temperature to be tested and incremented up to the highest temperature. The range of temperatures to be selected should produce resulting phase angle data, at a minimum, from 88 degrees or more through at least 75 degrees or less. Generally, this can be achieved with 3 temperatures although, there is no problem using more temperatures to achieve this range. Temperatures of 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C are the most common to use. However, some highly modified binders may require higher temperatures to achieve phase angles near 90 degrees. Likewise, some unmodified binders may require lower temperatures to achieve phase angle near 75 degrees (Refer to section 4.4 for temperature selection). Set the rheometer to have a thermal equilibrium time for each temperature to ensure the sample achieves thermal equilibrium with thermal gradients of no more than ± 0.1°C throughout the sample and free from thermal hysteresis. (refer to appendix X12 to determine appropriate time to achieve thermal equilibrium) Note 26—It is impossible to specify a single equilibration time that is valid for DSRs produced by different manufacturers. The design (fluid bath or air oven) of the environmental control system and the starting temperature will dictate the time required

C-27 to reach the test temperature. The method for determining the correct thermal equilibration time is described in Appendix X12. Note 27—The gap should be set at the starting test temperature (Section 11.1.1) or at the middle of the expected range of test temperatures (Section 11.1.2). See Note 5 for guidance on setting the gap. Typically, reliable test results may be obtained with a single sample, 25-mm plate, using temperatures within 12°C of the temperature at which the gap is set. Set the temperature controller to the desired test temperature, including any offset as required by Section 9.4.4. Allow the temperature indicated by the RTD to come to the desired temperature. The test shall be started only after the temperature has remained at the desired temperature ± 0.1°C for long enough to ensure the sample is completely at thermal equilibrium. . (refer to appendix X12 to determine appropriate time to achieve thermal equilibrium) When conducting test; 1) start testing at the lowest frequency and increase to the highest frequency 2) start the temperature from the lowest temperature and increase to the highest temperature. The data acquisition system specified in Section 6.1.4 automatically calculates G* and  from test data acquired when properly activated to generate isotherms for each frequency sweep at each temperature. Initiate the testing immediately after preparing and trimming the specimen. The testing at subsequent temperatures should be done as quickly as possible to minimize the effects of molecular associations (steric hardening) or sample edge failure that can cause changes in reported modulus which can occur if the specimen is held in the rheometer for a prolonged period of time. When testing at multiple temperatures all testing should be completed within four hours. Inspect the sample at the completion of the testing to ensure it has not excessively dripped out of the gap between the plates. If additional testing is needed to collect the required data and the sample appears intact, it can be used. It is also possible to remove and load a fresh sample for additional testing. ______________________________________________________________________ ANALYSIS & INTERPRETATION OF RESULTS Verification of the linear visco-elastic region. The dynamic modulus and phase angle depend upon the magnitude of the shear strain; the modulus and phase angle for both unmodified and modified asphalt binder decrease with increasing shear strain outside the linear visco-elastic region of the asphalt sample as shown in Figure 5. A plot such as that shown in Figure 5 can be generated by gradually increasing applied strain amplitude on the sample and

C-28 measure the resulting stress, thereby producing a strain sweep results in Figure 5. It is not necessary to generate such sweeps during normal testing; however, such plots are useful for verifying the limits of the linear region. Figure 5—Example of Strain Sweep A linear region may be defined at small strains where the modulus is relatively independent of shear strain. This region will vary with the magnitude of the complex modulus. The linear region is defined as the range in strains where the complex modulus is 95 percent or more of the zero-strain value. The shear stress varies linearly from zero at the center of the plates to a maximum at the extremities of the plate perimeter. The shear stress is calculated from the applied or measured torque, measured or applied strain, and the geometry of the test specimen. Report values of complex shear modulus and phase angle at each temperature obtained by frequency sweep. Omit all outliers/results where the measured strain and/or stress are outside of the measurable range of the instrument. Construct graph showing all frequency sweeps results. Graph G* & phase angle vs. frequency. (refer to X13) Create a master curve of the isotherms at the reference temperature of 80°C. (refer to X14) Identify from the master curve the frequency where the phase angle (δ) crosses 86 degrees. (refer to X14)

C-29 Construct Black space graph by plotting the phase angle vs. complex shear modulus to verify data. (Refer to X15) A continuous curve on the Black space graph indicates a successful data set has been used to create the master curve. (Refer to X15) Calculate mixing & compaction temperature from the resulting data from item 12.5.1 in accordance to reference X16. Use the following equation to determine laboratory compaction temperature in ºF. Mixing Temperature (ºF) = 325ω-0.0135 (X16) Where ω = the frequency in rad/s for the phase angle of 86 degrees as reported from the master curve. 12.2.4 Use the following equation to determine laboratory compaction temperature in ºF. Compaction Temperature (ºF) = 300ω-0.012 (X17) Where ω = the frequency in rad/s for the phase angle of 86 degrees as reported from the master curve. 12.2.4 _______________________________________________________________________ REPORT A sample report format is given in Appendix X13. Provide a complete identification and description of the material tested including name, code, and source. Describe the instrument used for the test including the model number and type of temperature control (ie, wet fluid immersion, dry forced gas, dry radiant, dry directly heated plates). The strain and stress levels specified in Tables 2 and 3 have been selected to ensure a common reference point that has been shown to be within the linear region for plain and modified asphalt binders. Some systems may not be linear within this region. When this situation is observed report the modulus at the recommended stress or strain levels but report that the test conditions were outside the linear region. For each test, report the following: Test plate diameter, nearest 0.1 mm and test gap, nearest 1μm; Test temperature, nearest 0.1°C, for the reported frequency of 13.4.3;

C-30 Frequency (to the nearest 10%), rad/s as derived from the master curve for Phase Angle of 86 degrees; Strain amplitude, nearest 0.01 percent, for the reported frequency of 13.4.3 Complex modulus (G*) corresponding to the phase angle of 86 degrees, kPa to three significant figures; Binder PG grade Mix Temperature to the nearest degree, oF ; Compaction Temperature to the nearest degree, oF. _______________________________________________________________________ PRECISION AND BIAS Precision—Criteria for judging the acceptability of dynamic shear results obtained by this method are given in Table 4. Single-Operator Precision (Repeatability) — Have not been determined as of yet. Multi-laboratory Precision (Reproducibility) — Have not been determined as of yet. Bias—No information can be presented on the bias of the procedure because no material having an accepted reference value is available. ________________________________________________________________________ KEYWORDS Dynamic shear rheometer; DSR; complex modulus; phase angle, asphalt binder; mix, mix temperature; compaction, compaction temperature; casola method, tts, time temperature superposition., NCHRP 9-39 ________________________________________________________________________ APPENDIXES _____________________________________________________________ _____________________________________________________________ X1. TESTING FOR LINEARITY X1.1. Scope: X1.2. This procedure is used to determine whether an asphalt binder exhibits linear or non- linear behavior at the testing temperature, e.g., 40, 50, 60, 70, 80, or 90°C. The determination is based on the change in complex shear modulus at 10 rad/s when the strain is increased from 2 to 20 percent. X1.3. Procedure:

C-31 X1.4. Verify the DSR and its components in accordance with Section 9 of this standard. X1.5. Prepare the DSR in accordance with Section 10 of this standard. X1.6. Prepare a test specimen for testing with 25-mm plates as per Section 11 of this standard. Select the test temperature for the binder in question. X1.7. Determine the complex shear modulus at 2 and 12 percent strain following the test procedure described in Section 12 except as noted below. Always start with the lowest strain and proceed to the next larger strain. X1.8. Strain Controlled Rheometers—If the software provided with the DSR will automatically conduct tests at multiple strains, program the DSR to obtain the complex shear modulus at strains of 2 to 20 percent in 2% increments. If this automatic feature is not available, test by manually selecting strains of 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 percent strain. X1.9. For stress controlled rheometers, compute the starting stress based on the complex shear modulus, G*, and shear stress, τ, as determined at the upper grading temperature during the grading of the binder. At this temperature the complex modulus, G*, will be greater than or equal to 1.00 kPa and the shear stress, τ, will be between 0.090 and 0.150 kPa (see Table 2). Calculate the starting stress as τ /6.00 kPa. Increase the stress in five increments of τ /6.00 kPa. Note X1.1—Sample calculation: Assume a PG 64-22 asphalt binder with G* = 1.29 kPa at 64°C and τ. = 0.135 kPa. The starting stress will be 1.35kPa/6 = 0.225 kPa. Test at 0.225, 0.450, 0.675, 0.900, 1.13, and 1.35 kPa, starting with 0.225 kPa. X1.10. Plot of Complex Modulus Versus Strain—Prepare a plot of complex shear modulus versus percent strain as shown in Figure 5. From the plot, determine the complex shear modulus at 2 and 12 percent strain. X1.11. Calculations: X1.12. Calculate the modulus ratio as the complex shear modulus at 12 percent strain divided by the complex shear modulus at 2 percent strain. \ X1.13. Report: X1.14. Report the following: X1.15. Complex shear modulus (G*) to three significant figures, X1.16. Strain, nearest 0.1 percent, X1.17. Frequency, nearest 0.1 rad/s, and X1.18. The ratio calculated by dividing the modulus at 12 percent strain by the modulus at 2 percent strain.

C-32 X1.19. Data Interpretation: X1.20. The measurement was performed in the non-linear range of the material if the modulus ratio as calculated in Section X1.11 is < 0.900 and linear if ≥ 0.900. If the measurement does indicate the linear region to be other than 12%, the maximum strain within the linear region may be used. _______________________________________________________________________ X2. CONTROL CHART X2.1. Control Charts: X2.2. Control charts are commonly used by various industries, including the highway construction industry, to control the quality of products. Control charts provide a means for organizing, maintaining and interpreting test data. As such, control charts are an excellent means for organizing, maintaining, and interpreting DSR verification test data. Formal procedures based on statistical principles are used to develop control charts and the decision processes that are part of statistical quality control. A quality control chart is simply a graphical representation of test data versus time. By plotting laboratory measured values for the reference fluid in a control chart format, it is easy to see when: X2.2.1. The measurements are well controlled and both the device and the operator are performing properly. X2.2.2. The measurements are becoming more variable with time, possibly indicating a problem with the test equipment or the operator. X2.2.3. The laboratory measurements for the fluid are, on the average above or below the target (reference fluid) value. Many excellent software programs are available for generating and maintaining control charts. Some computer-based statistical analysis packages contain procedures that can be used to generate control charts. Spreadsheets such as Microsoft’s Excel can also be used to generate control charts and, of course, control charts can be generated manually. (See Table X3.1 as an example print-out). X2.3. Care in Selecting Data: X2.3.1 Data used to generate control charts should be obtained with care. The idea of randomness is important but need not become unnecessarily complicated. An example will show why a random sample is needed—a laboratory always measures the reference fluid at the start of the shift or workday. These measurements could be biased by start-up errors such as a lack of temperature stability when the device is first turned on. The random sample ensures that the measurement is representative of the process or the material being tested. Said another way, a random sample has an equal chance of being drawn as any other sample. A measurement or sample always taken at the start or end of the day, or just before coffee break, does not have this chance.

C-33 ________________________________________________________________________ X.3 Example X3.1. The power of the control chart is illustrated in Table X3.1 using the verification data obtained for the DSR. Other DSR verification data suitable for a quality control chart presentation includes measurements for determining the temperature correction, calibrating the electronic thermometer, and maintaining data from internally generated asphalt binder reference samples. For this example, the reported viscosity for the reference fluid is 271 Pa-s; hence, the calculated value for G* is 2.71 kPa. This value for G* is labeled as “G* from Reference Fluid” in Figure X3.1. The laboratory should obtain this value on average if there is no laboratory bias. Table X3.1—Sample Test Data Week Measured G*, kPa 1 2.83 2 2.82 3 2.77 4 2.72 5 2.69 6 2.72 7 2.77 8 2.75 9 2.71 10 2.82 11 2.66 12 2.69 13 2.75 14 2.69 15 2.73 16 2.77 17 2.72 18 2.67 19 2.66 20 2.78 21 2.74 22 2.69 Average 2.73 Std. Dev. 0.051 CV % 1.86 X3.2. Comparison of 22-Week Laboratory Average for G* with Value Calculated from Reference Fluid: X3.2.1. The 22-Week average of the laboratory measurements is labeled as “22-Week Laboratory Average” in Figure X3.1. Over the 22 weeks, for which measurements were made, the average was 2.73 kPa. This value compares favorably with the calculated reference value, 2.71 kPa, differing on the average by only 0.7 percent. There appears to be little laboratory bias in this data. X3.3 Comparison of CV of Laboratory Measurements with Round Robin CV:

C-34 X3.3.1. From a previous round robin study, the within laboratory standard deviation (d1s) for the fluid was reported as 0.045 (CV = 1.67 percent). The 22-week standard deviation for the measured values of G* is 0.051 CV = 1.86 percent), as compared to 0.045 (CV =1.67 percent) reported from the round robin. However, it should be pointed out that the 22- week CV, 1.86 percent, also includes day-to-day variability, a component of variability not included in the round-robin d1s value. Based on this information the variability of the laboratory measurements are acceptable. X3.4 Variability of Measured Values: X3.4.1 In Figure X3.1, the value of G* calculated from the reference fluid is shown as a solid line. Also shown are two dotted lines that represent the G* calculated from the reference fluid ± 2 d1s where d1s is the value from the round robin. The calculated reference value for the fluid is 2.71 kPa, and the standard deviation is 0.045. Thus, a deviation of 2 d1s gives values of: 2.71kPa ± (2) (0.045) = 2.80 kPa, 2.62 kPa (X3.1) If the laboratory procedures are under control, the equipment is properly calibrated, and there is no laboratory bias, 95 percent of the measurements should fall within the limits 2.62 kPa and 2.80 kPa. Laboratory measurements outside this range are suspect, and the cause of the outlier should be investigated. The outlier may be the result of either testing variability or laboratory bias. The measurement from Week 10 in Figure X3.1 falls outside the ±2 d1s limits and is cause for concern such that testing procedures and verification should be investigated. If a measurement deviates from the target, in this case G* from the reference fluid, by more than ±3 d1s, corrective action should be initiated. The ±3 d1s limits 99.7 percent of the measured values if the laboratory procedures are under control and the equipment is properly calibrated. X3.5. Trends in Measured Value: X3.5.1 The control chart can also be used to identify unwanted trends in the data. For example, from weeks one to five, a steady decrease in the measured value is observed. This is cause for concern and the reason for the trend should be investigated. More sophisticated rules for analyzing trends in control charts can be found elsewhere.

C-35 Figure X3.1—Control Chart ________________________________________________________________________ X4. USE OF REFERENCE FLUID X4.1. Source of Reference Fluid: X4.2. An organic polymer produced by Cannon Instrument Company as Viscosity Standard N2700000SP has been found suitable as reference fluid for verifying the calibration of the DSR. The viscosity of the fluid, as determined from NIST–traceable capillary viscosity measurements, is approximately 270 Pa-·s at 64°C. However, the viscosity of the fluid varies from one lot to the next. The lot-specific viscosity is printed on the label of the bottle. ________________________________________________________________________ X5. CAUTIONS IN USING REFERENCE FLUID X5.1 Some items of caution when using the reference fluid are: X5.1.1 The fluid cannot be used to verify the accuracy of the phase angle measurement. X5.1.2. The fluid must not be heated as heating can degrade the fluid causing a change in its viscosity. X5.1.3 The fluid should be used for verification only after the DSR temperature measurements are verified. X5.1.4. The fluid cannot be used to calibrate the torque transducer. The manufacturer or other qualified service personnel using a calibration device designed specifically for the rheometer should perform the calibration. These calibration devices are typically not available in operating laboratories.

C-36 X5.1.5. When tested at 10 rad/s, the reference fluid should only be used at 64°C and above. At lower temperatures, the fluid is viscoelastic; hence, the viscosity, η, reported on the certificate by Cannon will not match the complex viscosity η* = G*/10 rad/s determined from the measurement. X5.1.6. Bubbles in the fluid will have a dramatic effect on the measured value of G*. The fluid in the bottle should be free of bubbles and care must be taken not to introduce bubbles when preparing test specimens. Recommended procedures for preparing test specimens are given in Section X6. _______________________________________________________________________ X6. RELATIONSHIPS BETWEEN OSCILLATION (DYNAMIC SHEAR) AND STEADY FLOW (STEADY SHEAR). CALCULATION OF G* FROM STEADY-STATE VISCOSITY MEASUREMENTS AND CALCULATION FROM G’ TO N1. X6.1. Among the different methods for converting between dynamic and steady-state viscosity of polymers, the most popular and most successful is the so-called Cox-Merz empirical rule. The rule leads, in simplified terms, to the following approximation. G*/ω = η* η ~ η* [where ω = ] (X6.1) where: G* = the complex modulus in Pa, ω = the angular frequency in radians/s, in oscillation η* = the complex viscosity as measured in oscillation, in Pa . s. N1 = Normal Force in N, generated in shear = the angular velocity in s-1 η = the shear rate independent capillary viscosity as reported by the supplier of the reference fluid (and steady shear viscosity as measured in the DSR) G’ = the storage modulus in Pa For this rule to apply the measurements must be in the viscous region where the phase angle approaches 90 degrees. The value of the complex modulus is then simply 10 times the value of the capillary viscosity. For example, if the capillary viscosity is 270,000 mPa-s the complex modulus is: G*, kPa ≈ (270,000 mPa•s)(1 kPa/1,000,000 mPa) (10 rad/s) = 2.70 kPa•rad (X6.2) The reference fluid behaves as a viscous fluid at 64°C and above and provides very accurate estimates of G* above 64°C. At temperatures below 58°C the fluid gives incorrect values for G* with the error increasing as the temperature departs from 64°C. At 64°C and above G* divided by the frequency in radians per second should be no more than three percent different than the viscosity printed on the bottle label. If this is the case, then the torque calibration should be considered suspect. N1 = 2(G’) [where ω = ] Is the elastic relationship when testing between dynamic shear and steady shear where the angular frequency is equal to the angular velocity.

C-37 ______________________________________________________________________ X7. METHODS FOR TRANSFERRING THE FLUID TO THE TEST PLATES X7.1. Three different methods are recommended for transferring the fluid to the test plates: X7.2. The glass rod method (Section X7.1), the spatula method (Section C4.3), and a direct method where a removable test plate is held in direct contact with the fluid in the bottle (Section C4.4). X7.3. Glass Rod Method (Figure X7.1): X7.3.1 In this method, a glass rod is inserted into the fluid and rotated (Step 1) while in the fluid. Continue rotating the rod, and pull it slowly from the fluid (Step 2) carrying a small mass of the fluid with the rod. Touch the mass to the plate (Step 3) to transfer the fluid to the plate. See Figure X7.1. Figure X5.1 (Figure not included)⎯Using a Glass Rod to Place the Reference Fluid on the Plate X7.4. Spatula Method (Figure X7.2): X7.5. When carefully used a spatula may be used to transfer the fluid. Special care must be taken not to trap air as the material is scooped from the bottle, Step 1. Smear the mass on the spatula onto the plate (Step 2) and cut the mass from the spatula by drawing the spatula across the edge of the plate (Step 3). This method appears to be the most difficult to implement and is the least recommended of the three methods. Figure X7.2 (Figure not included)⎯Using a Spatula to Place the Reference Fluid on the Plate X7.6 Direct Touch Method (Figure X7.3)—If the rheometer is equipped with plates that may be removed and reinstalled without affecting the gap reference, remove one of the plates and touch the surface of the plate to the surface of the fluid in the bottle (Step 1). Pull the plate from the bottle, bringing a mass of the fluid along with the plate (Step 2). Invert the plate and allow the fluid to flow out into a mushroom shape (Step 3). Figure X7.3 (Figure not included)⎯Direct Touch Method to Place the Reference Fluid on the Plate Proceed immediately to Section 10.5 to trim the reference fluid specimen and form the bulge. Proceed with testing the reference fluid specimen as described in Section 11.

C-38 ______________________________________________________________________ X8. SELECTION OF GAP CLOSURE TO OBTAIN BULGE X8.1. Need for Accurate Measurement of Specimen Diameter: X8.2. The accuracy of the DSR measurements depends upon an accurate measurement of the diameter of the test specimen. The diameter of the test specimen is assumed equal to the diameter of the test plates. For this reason, the trimming of excess binder and the final closure of the gap to produce a slight bulge in the test specimen are critical steps in the DSR test procedure. When the gap is closed to its final dimension, the bulge must be of sufficient size to compensate for any shrinkage in the binder and consequently avoiding a concave surface as shown in Figure X8.1. The diameter of the test specimen in Figure X8.1 approaches d, rather than d', the diameter of the plate. The modulus, G*, is calculated according to the following equation: |G*|=(2h/πr4)⋅(τ/Θ) (X8.1) where: G* = Complex modulus τ = Torque applied to test specimen h = Thickness of test specimen Θ = Angular rotation, radians r = radius of test plate Figure X8.1 (Figure Not Included)—Concave Surface Resulting from Insufficient Closure after Trimming Figure X8.2 (Figure Not Included)—Proper Bulge X8.3 According to Equation X8.1, the modulus depends upon the radius (or diameter) raised to the fourth power. Therefore, a small concavity in the outer surface of the test specimen, as shown in Figure X8.1, will have a large effect on the measured modulus because the actual specimen diameter will be less than the plate diameter. For a given amount of concavity, the effect on the measured modulus is greater for the 8-mm plate than the 25- mm plate. A more desirable result is a slight bulge as illustrated in Figure X8.2. Shear stresses are not transferred directly from the plate to the overhanging binder; therefore, the effect of a slight bulge on the measured modulus is much less than a slight concavity. It should be noted that errors in the diameter of the test specimen do not affect the measured values of the phase angle. _______________________________________________________________________ X9. RECOMMENDED GAP CLOSURE VALUES X9.1 Recommended values for the gap closure required to form a bulge at the test temperature similar to the bulge illustrated in Figure X8.2 are given in Section 10.5 as 50 µm and 100 µm for the 25-mm and 8-mm plates, respectively. Although these values may be appropriate for many rheometers, they may not be appropriate for all rheometers. The applicability of these values to a specific rheometer may be determined by preparing a test specimen using the recommended closure and observing the shape of the bulge after the final closure of the gap and after the test specimen is at the test temperature. If the recommended closure values do not give an appropriate bulge, the recommended closure values should be adjusted as appropriate.

C-39 Proper and improper bulges are shown in Figures X10.1 through X10.3. A magnifying glass is useful for examining the shape of the bulge. Regardless of the closure required to produce a desirable bulge, the actual gap should be used in the calculations. _______________________________________________________________________ X10. FACTORS AFFECTING BULGE DEVELOPMENT X10.1 A number of factors can affect the bulge formed at the test temperature. These include: X10.2. The amount of closure used to create the bulge. X10.3. The difference in temperature between the trimming temperature, the temperature at which the bulge is created, and the test temperature. X10.4. Thermal expansion-contraction characteristics of the rheometer. X10.5. Thermal contraction and expansion of the asphalt binder. A concave surface is more likely to form at the intermediate temperatures, than at the upper test temperatures (8-mm plate rather than the 25-mm plate). In fact, at the higher test temperatures excessive material can be squeezed from the plates as shown in Figure X10.3. This situation should also be avoided and may require gap closures somewhat less than the recommended values. Figure X10.1—Good Bulge Size Figure X10.2—Concave Bulge Figure X10.3—Oversized Bulge ________________________________________________________________________

C-40 X11. DETERMINATION OF TIME TO THERMAL EQUILIBRIUM X11.1.1 Reason for Determining Time Required to Obtain Thermal Equilibrium: X11.1.2 After the test specimen has been mounted in the DSR, it takes some time for the asphalt binder between the test plates to reach thermal equilibrium. Because of thermal gradients within the test plates and test specimen, it may take longer for the test specimen to come to thermal equilibrium than the time indicated by the DSR thermometer. Therefore, it is necessary to experimentally determine the time required for the test specimen to reach thermal equilibrium. X11.1.3. The time required to obtain thermal equilibrium varies for different rheometers. Factors that affect the time required for thermal equilibrium include: X11.1.4. Design of the rheometer and whether air or liquid is used as a heating-cooling medium; water has roughly 25 times more thermal conductivity to that of air. Air conductivity is improved by increasing the velocity of air flow. X11.1.5. Difference between ambient temperature and the test temperature, different when testing below room temperature, and above room temperature, X11.1.6. Difference in temperature between the trimming and test temperature, and X11.1.7. Plate size, different for the 8-mm and 25-mm plate. X11.2. It is not possible to specify a single time as the time required to obtain thermal equilibrium. For example, thermal equilibrium of the asphalt sample is reached much quicker with liquid-controlled rheometers than with air-cooled rheometer. This requires that the time to thermal equilibrium be established for individual rheometers, typical trimming and testing temperatures, and testing conditions. ________________________________________________________________________ X12. METHOD TO DETERMINE THE TIME REQUIRED TO OBTAIN THERMAL EQUILIBRIUM FOR BOTH THE DSR & THE SAMPLE X12.1.1. The time to reach thermal equilibrium is the time required to reach a constant modulus regardless of heating to that temperature or cooling down to that temperature. Typically, this time will be greater than the time for the DSR reports on its display reading for temperature to be stable. The asphalt sample heats and cools much slower then the response of the environmental chamber. Thus, it is important to determine the precise time required for a DSR to achieve thermal equilibrium for the asphalt sample. X12.2. As a guide, safe values which can be used with most modern are as follows. Rheometers using a total fluid immersion principle of the sample in water will require a minimum of 3 minutes from the time the chamber stabilizes within ±0.1°C. A forced gas oven will require a minimum of 60 minutes from the time the chamber stabilizes within ±0.1°C. Refer to the manufacturer for specific help to determine the required time to stabilize the

C-41 sample for accurate asphalt measurements for specific DSR model. Dry directly heated plates or oven chambers employing radiant heating or not pre-conditioned gas may take significantly longer then 60 minutes to achieve thermal equilibrium on the asphalt sample with acceptable thermal gradients. X12.3. The following procedure can be used to determine the appropriate time required to achieve sample thermal equilibrium for a specific DSR. X12.3.1 A reliable estimate of the time required for thermal equilibrium can be obtained by monitoring the DSR temperature and the complex modulus of a sample mounted between the test plates. Because the modulus is highly sensitive to temperature, it is an excellent indicator of thermal equilibrium. The following procedure is recommended for establishing the time to thermal equilibrium: X12.3.2. Mount a binder sample in the DSR and trim in the usual manner. Create a bulge and bring the test chamber or fluid to the test temperature. X12.3.3. Operate the DSR in a continuous mode at 10 rad/s using an unmodified asphalt binder sample—one that does not change modulus with repeated shearing. If testing at grade temperature use 10% strain. If testing at other then grade temperature, use the smallest strain value that gives good measurement resolution. X12.3.4. Perform a series of temperature steps, each held for at least 2000 seconds, while recording the modulus at 30 s time intervals. These steps should approach the nominal temperature from heating and cooling in order to identify any thermal hysteresis within the sample. Results should be displayed on a plot of the modulus versus time (Figure X12.1). As the example in Figure X12.1, the temperature profile was 70°C, 76°C, 70°C, 64°C, 70°C, 76°C, 70°C. Results as shown in Figure X12.1. can be graphed as an overlay of G* to permit the comparison of the 70°C results of modulus as shown in (Figure X12.2). Where the G* data for 70°C overlay defines the instrument’s time to reach thermal equilibrium. In this example, the time to thermal equilibrium is reported as 0.6k seconds (600 seconds).

C-42 Figure X12.1—Results of the test to determine a DSR’s temperature performance Figure X12.2—Comparison of Modulus at 70C; Thermal equilibrium reached where the center G* values agree (at about 500sec in this example) X12.3.5. By approaching the nominal temperature from both heating and cooling, enables the identification of actual Thermal Equilibrium from the effects of apparent thermal hysterisis. Thermal hysteresis is the effect of the inefficient thermal conductivity of the environmental chamber in which the sample core or sample edge contains greater then the required ±0.1°C thermal gradient over the time permitted to achieve thermal equilibrium The appearance of thermal equilibrium may be mistaken for the slow response of the asphalt to change temperature as asphalt is a poor thermal conductor. This effect is obvious in Figure X12.3. Given longer time to achieve thermal equilibrium the amount of thermal hysteresis should reduce.

C-43 Figure X12.3—Identifying Thermal Hysteresis; G* does not recover post. X12.3.6. Once the DSR’s time to thermal equilibrium has been identified, a small buffer time of 2 minutes should be added as a conditioning period to the testing programmed time for equilibrium. From the example of Figure X12.3., where the DSR’s time to thermal equilibrium is 600 seconds (DSR TE), and the additional conditioning buffer of 120 seconds gives the total time to use for testing as 720 seconds. Testing thermal equilibrium (Sample TE would be 720 seconds (12min), as shown in (Figure X12.4.).

C-44 Figure X12.4—Identifying the Sample time for Thermal Equilibrium X12.4. Because the time required to reach thermal equilibrium can vary with the test temperature and testing conditions, the time to thermal equilibrium should be established separately for any new testing protocol. Once the time to thermal equilibrium has been established, it does not have to be repeated unless the test conditions change. ________________________________________________________________________

C-45 X13. EXAMPLE OF FREQUENCY SWEEP ISOTHERMS X13.1 Graph of G* and phase angle for each of the individual frequency sweeps at each temperature on a single graph (Figure X13.1) Figure X13.1-Graph of frequency sweeps for each temperature. X14. EXAMPLE OF MASTER CURVE AT 80°C AND DETERMINATION OF FREQUENCY WHERE THE PHASE ANGLE IS EQUAL TO 86 DEGREES. X14.1. Display of Isotherms (Figure X14.1) The example in Figure X14.1 shows 4 sets of isotherms for an asphalt binder.

C-46 Figure X14.1- Graph of Isotherms. X14.2. Performing the Time Temperature Superposition model to the data using a reference temperature of 80°C would produce the master curve shown in Figure X14.2. Figure X14.2.- Master Curve created to an 80°C reference from isotherms. X14.3. From the master curve, identify the phase angle of 86 degrees and determine the frequency at which it occurs (Figure X14.3). Most modern DSRs provide features within their software in which enables the operator the ability to identify specific points from the graph or table. In the event the exact value is not provided, interpolate between the two nearest points bracketing the 86 degree value. The exactness required for the reporting of frequency in this process is ±10%. Small errors in reporting have little to no effect on the final determination of both mixing & compaction temperature.

C-47 Figure X14.3- Determination of Frequency at a phase angle of 86 degrees from the master curve _______________________________________________________________________ X15. VERIFICATION OF MASTER CURVE WORKING DATA BY USING BLACK SPACE DIAGRAM X15.1 A good example of a Black Space diagram where there is shown a continuous curve exhibited in the results (Figure X15.1). This is where there are not obvious discontinuities. FIGURE X15.1- Good example of Black Space diagram X15.2. A poor example of a Black Space diagram, where there are obvious discontinuities in the results (Figure X15.2). In the case of a poor Black Space, the data should be retested with particular attention to ensuring all the data are collected in the linear visco-elastic region by ensuring the correct strains are applied properly to all frequencies and that the temperatures are correct for each frequency tested. (Figure X15.2)

C-48 FIGURE X15.2- Poor example of Black Space diagram X16. DETERMINATION OF LABORATORY MIXING TEMPERATURE X16.1. Use the following equation to determine laboratory compaction temperature in ºF. Mixing Temperature (ºF) = 325ω-0.0135 (X16) Where ω = the frequency in rad/s for the phase angle of 86 degrees as reported from the master curve. 12.2.4 ________________________________________________________________________ X17. DETERMINATION OF LABORATORY COMPACTION TEMPERATURE X17.1. Use the following equation to determine laboratory compaction temperature in ºF. Compaction Temperature (ºF) = 300ω-0.012 (X17) Where ω = the frequency in rad/s for the phase angle of 86 degrees as reported from the master curve. 12.2.4 ________________________________________________________________________

C-49 X18. SAMPLE REPORT Header Information: Item Data Group 1 Item Data Group 2 Operator’s Name: 24 Alpha-Numeric Date of Test (dd/mm/yy): __/__/__ Test Specimen ID No.: 18 Alpha Time of Test (hr:min): __:__ Project ID No.: 12 Alpha-Numeric DSR Manufacturer: 12 Alpha-Numeric File Name: 12 Alpha-Numeric DSR Model: 12 Alpha-Numeric Sample Grade: 12 Alpha-Numeric DSR Serial Number Or Other Identifying ID No.: 18 Alpha-Numeric Frequency, rad/s for Phase Angle of 86 degrees at a temperature of 80°C 0.000 Software Version: 12 Alpha-Numeric Mix Temperature, °F 000 Compaction Temperature, F 000 ________________________________________________________________________

C-50 X19. REFERENCES X19.1. Anderson, D. A. and M. Marasteanu. “Manual of Practice for Testing Asphalt Binders in Accordance with the Superpave PG Grading System.” The Pennsylvania Transportation Institute, The Pennsylvania State University, PTI 2K07, November 1999 (Revised February 2002). X19.2. Wadsworth, H., ed. Handbook of Statistical Methods for Engineers and Scientists. McGraw-Hill, New York, NY, 1990. X19.3. Anderson, D. A., C. E. Antle, K. Knechtel, and Y. Liu. Interlaboratory Test Program to Determine the Inter- and Intra-Laboratory Variability of the SHRP Asphalt Binder Tests. FHWA, 1997. X19.4. Cox, W. P. and E. H. Merz. Correlation of Dynamic and Steady Flow Viscosities, Journal of Polymer Science, Volume 28, 1958, pp. 619–622. X19.5. West, R. Procedure for Determining Mixing and Compaction Temperatures of Asphalt Binders in Hot Mix Asphalt, NCHRP Report XXX, 2008.

Next: Appendix D - Statistical Analyses of the Steady Shear Flow and Phase Angle Methods »
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 648: Mixing and Compaction Temperatures of Asphalt Binders in Hot-Mix Asphalt explores enhanced test methods for determining laboratory mixing and compaction temperatures of modified and unmodified asphalt binders.

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