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

Chapter: Chapter 3 - Findings and Applications

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Suggested Citation:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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:"Chapter 3 - Findings and Applications." 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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33 Experimental Results Binder Testing This section summarizes the results from all of the binder tests including Superpave performance grading of the binders, mixing temperatures from the equiviscous method and the three candidate methods, SEP tests, multi-stress creep recov- ery tests, and analyses of binder degradation following the SEP test. Binder Grading Table 8 lists the Superpave performance grades of the binders as reported by the supplier/producer and the results of the grading conducted by NCAT. In this table and in all subsequent tables showing the study binders, the binders are sorted by their high temperature true grade as a simple way of putting the binders in a rational order. Modified binders are identified by shaded rows. Binder L, which contained ground tire rubber as a modifier, was not able to be graded or tested in DSR equipment due to apparent incompatibility of the rubber particles and the asphalt. Therefore, binder L was not included in the results or analysis. Based on NCAT’s binder grading results, nearly half of the binders did not meet the requirements for the Super- pave binder grade as reported by the supplier. The discrep- ancies between the producer’s grades and the results from NCAT were mostly due to low temperature properties. Binder G actually met a higher grade than the supplier reported. However, the differences between the reported grade and NCAT results are generally fairly small and probably not signif- icant considering lab variability of the tests. The NCAT results are used throughout the analysis to sort the binders and to serve as a baseline for evaluating changes due to heating the binders to elevated temperatures. High Shear Rate Viscosity Method Table 9 shows the mixing and compaction temperature results from the high shear rate viscosity tests performed using Yildirim’s approach. The table also shows the mixing and compaction temperatures from the equiviscous method for comparison. It can be seen from these data that the tem- peratures from the high shear rate viscosity method are very similar to the equiviscous method for most of the binders. Mixing temperatures for all of the modified binders are greater than 350°F, with most above 360°F. Since modified binder results from the high shear viscosity method are exces- sive and the method provides essentially no improvement compared with the equiviscous method, further analysis of the high shear rate viscosity method is not included in this report. Steady Shear Flow Method Table 10 shows the results from the Steady Shear Flow method. These mixing and compaction temperatures are substantially lower than the equiviscous mixing and com- paction temperatures. The differences between the two meth- ods are greater for modified binders, which indicates that many of these binders exhibit shear thinning (i.e., lower viscosity at higher shear rates) behavior. The steady shear flow method also yields lower mixing and compaction tempera- tures for the unmodified binders: in most cases, the mixing temperatures are more than 10°F lower than the equiviscous mixing temperatures. Phase Angle Method Mixing and compaction temperatures determined using the Phase Angle method are shown in Table 11. For the modified binders, the mixing and compaction temperatures using the Phase Angle method are substantially lower than from the equiviscous method. For the unmodified binders, C H A P T E R 3 Findings and Applications

some of the mixing and compaction temperatures from the Phase Angle method are lower and some are higher than from the equiviscous method. SEP Tests Table 12 shows a summary of the opacity results from the SEP tests on the binders. Although these data show that emis- sions increase with higher temperatures, the amount and rate of emissions increase differs among the binders. In order to properly compare the SEP opacity results for the binders in the experiment, the midpoint of the pro- ducer’s recommended mixing temperature range for each respective binder was determined and opacity was inter- polated at this temperature. This, in effect, normalized the opacity data to an appropriate reference temperature for each binder. These opacity values were then ranked and graphed in Figure 19. It can be observed from the SEP opacity data there is no apparent link between opacity and binder high grade, binder low grade, grade spread, or whether the binder is modified. Even binders from the same crude source—such as Binders B, C, and E, which were refined from the same Canadian crude—had markedly different opacity results. This finding 34 Binder ID Producer’s Reported Binder Grade NCAT results True Grade Grade Confirmed? Yes/No Comments M PG 82-22 85.5 -19.5 No Failed BBR N PG 82-22 84.3 -25.5 Yes G PG 76-22 82.5 -24.2 No Met higher grade H PG 76-22 78.3 -26.1 Yes C PG 70-34 75.1 -38.9 Yes I PG 70-28 71.8 -29.2 Yes B PG 64-40 69.3 -37.3 No Failed BBR F PG 64-22 67.8 -21.3 No Failed DTT O PG 64-28 65.6 -29.7 Yes K PG 64-16 65.3 -13.0 No Failed BBR & DTT J PG 64-16 64.3 -20.7 Yes E PG 58-34 60.9 -33.1 No Failed BBR D PG 58-28 60.3 -26.0 No Failed DTT Table 8. True grades of the research binders as determined by NCAT. Binder ID True Grade Mixing Temperature °F (°C) Compaction Temperature °F (°C) Equiviscous Method High Shear Rate Viscosity Equiviscous Method High Shear Rate Viscosity M 85.5 -19.5 372 (189) 363 (184) 343 (173) 336 (169) N 84.3 -25.5 433 (223) 433 (223) 401 (205) 401 (205) G 82.5 -24.2 379 (193) 372 (189) 352 (178) 349 (176) H 78.3 -26.1 365 (185) 363 (184) 338 (170) 338 (170) C 75.1 -38.7 388 (198) 385 (196) 355 (179) 352 (178) I 71.8 -29.2 333 (167) 333 (167) 311 (155) 311 (155) B 69.3 -37.3 354 (179) 352 (178) 325 (163) 325 (163) F 67.8 -21.3 320 (160) 318 (159) 298 (148) 297 (147) O 65.6 -29.7 318 (159) 318 (159) 293 (145) 297 (147) K 65.3 -13.0 295 (146) 295 (146) 271 (132) 275 (135) J 64.3 -20.7 295 (146) 295 (146) 275 (135) 273 (134) E 60.9 -33.1 293 (145) 293 (145) 273 (134) 297 (147) D 60.3 -31.7 295 (146) 297 (147) 275 (135) 279 (137) Table 9. Mixing and compaction temperatures from the high shear rate viscosity method.

does not agree with the conclusion from Stroup-Gardiner and Lange (31). Another example is the set of binders refined from the blend of Alaskan slope and Canadian crudes, D and I. These two binders also have substantially differ- ent opacity results at the producer’s recommended mixing temperature. Another measurement from the SEP test is the mass loss of the binders due to exposure to high temperatures. A sum- mary of the mass loss results are shown in Table 13. Mass loss also increased with higher SEP test temperatures for all of the binders. As with opacity, there does not appear to be a relationship between mass loss and binder high grade, low grade, grade spread, modified versus unmodified, or crude source. Mass loss and opacity are not strongly correlated, as shown in Figure 20. The trend shows that higher mass loss generally corresponds to higher opacity, but the relationship is not suit- able to use one measurement to predict the other. For some binder samples, mass loss may include the loss of molecular water rather than purely a loss of volatile organic components that would be better associated with opacity and changes in physical properties of the binder. 35 Binder ID True Grade Mixing Temperature °F (°C) Compaction Temperature °F (°C) Equiviscous Method Steady Shear Flow Viscosity Equiviscous Method Steady Shear Flow Viscosity M 85.5 -19.5 372 (189) 296 (147) 343 (173) 275 (135) N 84.3 -25.5 433 (223) 337 (169) 401 (205) 311 (155) G 82.5 -24.2 379 (193) 340 (171) 352 (178) 312 (156) H 78.3 -26.1 365 (185) 333 (167) 338 (170) 304 (151) C 75.1 -38.7 388 (198) 320 (160) 355 (179) 291 (144) I 71.8 -29.2 333 (167) 316 (158) 311 (155) 289 (143) B 69.3 -37.3 354 (179) 325 (163) 325 (163) 295 (146) F 67.8 -21.3 320 (160) 309 (154) 298 (148) 281 (138) O 65.6 -29.7 318 (159) 309 (154) 293 (145) 280 (138) K 65.3 -13.0 295 (146) 280 (138) 271 (132) 257 (125) J 64.3 -20.7 295 (146) 289 (143) 275 (135) 263 (128) E 60.9 -33.1 293 (145) 293 (145) 273 (134) 269 (132) D 60.3 -31.7 295 (146) 289 (143) 275 (135) 262 (128) Table 10. Mixing and compaction temperatures from the steady shear viscosity method. Binder ID True Grade Freq. at δ =86° T=80°C Mixing Temp. °F (°C) Compaction Temp. °F (°C) Equiviscous Method Phase Angle Method Equiviscous Method Phase Angle Method M 85.5 -19.5 0.07 372 (189) 337 (169) 343 (173) 310 (154) N 84.3 -25.5 0.03 433 (223) 341 (172) 401 (205) 313 (156) G 82.5 -24.2 0.03 379 (193) 341 (172) 352 (178) 313 (156) H 78.3 -26.1 0.22 365 (185) 332 (167) 338 (170) 305 (152) C 75.1 -38.7 0.21 388 (198) 332 (167) 355 (179) 306 (152) I 71.8 -29.2 2.98 333 (167) 320 (160) 311 (155) 296 (147) B 69.3 -37.3 1.10 354 (179) 325 (163) 325 (163) 300 (149) F 67.8 -21.3 75.00 320 (160) 307 (153) 298 (148) 285 (141) O 65.6 -29.7 21.12 318 (159) 312 (156) 293 (145) 289 (143) K 65.3 -13.0 800 295 (146) 297 (147) 271 (132) 277 (136) J 64.3 -20.7 580 295 (146) 298 (148) 275 (135) 278 (137) E 60.9 -33.1 37.85 293 (145) 309 (154) 273 (134) 287 (142) D 60.3 -31.7 122.56 295 (146) 305 (152) 275 (135) 283 (139) Table 11. Mixing and compaction temperatures from the Phase Angle Method.

36 ID True Grade Avg. opacity (%) at test temp. Std. dev. of opacity at test temp. 130°C 150°C 170°C 190°C 130°C 150°C 170°C 190°C 266°F 302°F 338°F 374°F 266°F 302°F 338°F 374°F M 85.5 -19.5 0.28 4.80 4.80 11.63 0.07 0.06 0.06 0.13 N 84.3 -25.5 0.35 0.39 0.42 0.79 0.09 0.05 0.04 0.05 G 82.5 -24.2 0.00 1.16 1.45 2.13 0.14 0.06 0.05 0.06 H 78.3 -26.1 0.22 2.83 5.27 13.21 0.11 0.08 0.4 0.78 C 75.1 -38.7 3.11 8.68 8.68 16.46 0.12 0.11 0.11 0.68 I 71.8 -29.2 0.23 4.41 10.21 16.62 0.08 0.22 0.54 1.09 B 69.3 -37.3 0.51 1.39 4.92 8.45 0.08 0.08 0.31 0.61 F 67.8 -21.3 0.00 1.09 1.16 2.12 0.09 0.07 0.05 0.05 O 65.6 -29.7 0.26 0.14 5.35 11.84 0.12 0.17 0.34 0.76 K 65.3 -13.0 0.00 3.17 7.02 19.26 0.09 0.06 0.26 0.48 J 64.3 -20.7 0.22 3.37 8.94 12.94 0.09 0.07 0.14 0.36 E 60.9 -33.1 0.55 2.48 8.50 27.40 0.08 0.12 0.56 0.87 D 60.3 -31.7 0.07 2.53 5.23 7.53 0.05 0.11 0.24 0.64 Table 12. Opacity results from SEP test. 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 N F E K G M O B D H J C I O pa ci ty % Figure 19. Ranked opacity results after normalizing to the midpoint of the producer’s recommended mixing temperature. ID True Grade Avg. Mass Loss (%) Std. Dev. of Mass Loss (%) 130°C 150°C 170°C 190°C 130°C 150°C 170°C 190°C 266°F 302°F 338°F 374°F 266°F 302°F 338°F 374°F M 85.5 -19.5 0.09 0.18 0.11 0.43 0.02 0.03 0.03 0.02 N 84.3 -25.5 0.31 0.55 1.99 2.76 0.09 0.06 0.06 0.06 G 82.5 -24.2 0.01 0.11 0.15 0.35 0.03 0.02 0.03 0.02 H 78.3 -26.1 0.02 0.23 0.23 0.20 0.03 0.03 0.02 0.02 C 75.1 -38.7 0.12 0.01 0.12 1.07 0.04 0.02 0.02 0.05 I 71.8 -29.2 0.12 0.23 0.63 1.09 0.03 0.02 0.03 0.04 B 69.3 -37.3 0.31 0.01 0.34 0.95 0.07 0.02 0.04 0.05 F 67.8 -21.3 0.12 0.09 0.06 0.09 0.04 0.03 0.04 0.02 O 65.6 -29.7 0.23 0.41 0.65 0.73 0.02 0.03 0.02 0.03 K 65.3 -13.0 0.06 0.20 0.20 0.51 0.04 0.03 0.02 0.03 J 64.3 -20.7 0.00 0.00 0.69 1.16 0.01 0.01 0.02 0.07 E 60.9 -33.1 0.00 0.12 0.56 1.11 0.01 0.03 0.02 0.06 D 60.3 -31.7 0.00 0.28 0.39 1.07 0.03 0.05 0.04 0.05 Table 13. Mass loss results from SEP Test.

Results of Re-Graded Binders Binder grading results for the original binder materials and the residues from the SEP tests are shown in Table 14. True grades for the samples are shown based on the critical low temperatures determined from the bending beam rheometer (BBR) test and the direct tension test (DTT). Also shown are the phase angles for each binder at the high PG temperature. These results are discussed in a later section regarding analy- sis of binder degradation. MSCR Tests Table 15 is a summary of the results from the MSCR tests. The information shown in this table is the non-recoverable creep compliance results that indicate the degree to which a binder recovers shear strains resulting from a range of stresses. Binders that are modified with elastomeric polymers will typ- ically exhibit a high degree of recovery or, inversely, have very low values of non-recoverable compliance. Following the AASHTO TP 70 protocol, binders are normally tested after rolling-thin-film oven (RTFO) conditioning at the binder’s high PG temperature. However, initial MSCR tests on RTFO- aged samples after the SEP procedure showed that the RTFO aging masked the effects of the SEP tests. Therefore, no RTFO conditioning was performed on the SEP-conditioned binders to better assess the effects of the SEP temperatures on the binders. For this study, the binders were tested after four temperatures (58°C, 64°C, 70°C, and 76°C) in the SEP test. MSCR tests were conducted on the original and SEP conditioned binder samples. Results are reported as non- recoverable creep compliance, Jnr, at two standard levels of stress, 100 and 3200 Pa. Example plots of the change in Jnr with increasing test temperature and SEP conditioning are shown in Figures 21 and 22. Results for a modified Binder, H, are shown in Fig- ure 21, and the results of an unmodified Binder, E, are shown in Figure 22. Note that the y-axis (Jnr) scales of these graphs are different. For all of the modified binders, the maximum Jnr was less than 20 1/Pa. However, for the unmodified binders, much of the data was above this level and, in one case (as shown in Figure 22), exceeded 100 1/Pa. Further analysis of these results is provided in the next section. Analysis of Binder Degradation Four binder characteristics were examined for evidence of binder degradation due to exposure to high temperatures: • Changes in the true grade critical high temperature of the binders; • Changes in the true grade critical low temperature of the binders; • Changes in the phase angle of the binders at their respec- tive grade temperatures; and • Changes in the MSCR non-recoverable creep compliance. Table 16 shows the change in the critical high temperatures, that is, the change in critical high temperature from the origi- nal, unaged binder to the re-graded binder after SEP condition- ing at each temperature (i.e., SEP residue Tc − Original Tc). The data show that the critical high temperatures increased with higher SEP temperatures. Increases in high temperature grades are considered beneficial to rutting resistance. This trend is expected since exposure to high temperatures increases molec- ular size through oxidation and polymerization and therefore stiffens the binders. The three binders with the greatest increase in the critical high temperature were I, O, and H. The high tem- perature grade for the air-blown Binder I changed the most with a two-grade increase. Those that changed the least were unmodified Binder K and modified Binder C, with an increase in critical high temperature of 4.6°C and 4.4°C, respectively. Although there are differences among the binders in the mag- nitude of change of the high temperature grade due to the SEP conditioning, there is no evidence of binder degradation from this data. Table 17 shows the change in the critical low temperature for the binders. For most binders, the critical low temperature after the SEP testing was based on the DTT. Overall, the low critical temperatures typically increased several degrees from the original binders, but not enough to change the grade for most binders. This indicates that pavements with these binders would be only slightly more likely to experience thermal crack- ing after exposure to the temperatures in the SEP test. Binders that had the greatest increase in critical low temperature were I, J, N and O. Of these, J, N, and O barely had a one-grade change at the low temperature end; Binder I did not change low temperature grade. There was no general trend of increas- ing critical low temperature with higher temperatures, and most modified binders increased slightly less than the unmodified binders. Therefore, there is no strong evidence of 37 y = 0.0424x + 0.1168 R2 = 0.5459 0 0.2 0.4 0.6 0.8 1 1.2 1.4 0 5 10 15 20 25 30 Opacity (%) M as s L o s s (% ) 130 C 150 C 170 C 190 C Figure 20. Comparison of mass loss and opacity data.

38 C°,erutarepmeTtseTPES Binder Test Original 130 150 170 190 M Original DSR 85.4 91.7 89.6 92.1 95.6 Phase Angle @ 82°C 65.8 64.1 65.2 65.8 62.4 RTFO DSR 65.8 64.1 65.2 65.8 62.4 PAV DSR 24.1 23.0 25.4 26.7 26.9 BBR Stiffness -26.4 -27.3 -26.1 -28.7 -27.7 BBR m-value -19.5 -17.7 -16.4 -17.3 -17.3 DTT -24.8 -17.7 -17.3 -19.6 -21.5 True Grade - BBR 85.4 -19.5 88.4 -17.7 89.6 -16.4 90.8 -17.3 92.2 -17.3 True Grade - DTT 85.4 -24.8 88.4 -17.7 89.6 -17.3 90.8 -19.6 92.2 -21.5 N Original DSR 96.6 88.9 94.6 98.7 97.7 Phase Angle @ 82°C 70.0 69.6 71.4 66.5 66.1 RTFO DSR 84.3 83.0 85.7 88.9 91.0 PAV DSR 15.0 25.7 23.2 20.2 24.3 BBR Stiffness -33.1 -23.5 -24.4 -30.0 -30.5 BBR m-value -25.5 -22.3 -24.1 -23.8 -27.0 DTT -27.8 -18.4 -20.3 -20.5 -20.8 True Grade - BBR 84.3 -25.5 83.0 -22.3 85.7 -24.1 88.9 -23.8 91.0 -19.5 True Grade - DTT 84.3 -27.8 83.0 -18.4 85.7 -20.3 88.9 -20.5 91.0 -20.8 G Original DSR 82.5 89.9 90.6 90.4 89.9 Phase Angle @ 76°C 67.1 64.0 63.3 61.8 63.1 RTFO DSR 85.5 94.3* 87.9 88.7 89.8 PAV DSR 20.3 22.5 22.2 18.6 20.9 BBR Stiffness -27.1 -27.2 -25.8 -28.1 -26.7 BBR m-value -24.2 -24.3 -23.4 -23.5 -22.3 DTT -25.6 -23.9 -22.3 -24.3 -21.2 True Grade - BBR 82.5 -24.2 89.9 -24.3 87.9 -23.4 88.7 -23.5 89.8 -22.3 True Grade - DTT 82.5 -25.6 89.9 -23.9 87.9 -22.3 88.7 -24.3 89.8 -21.2 H Original DSR 78.7 81.5 85.9 86.3 88.4 Phase Angle @ 76°C 72.3 70.2 68.4 67.7 66.7 RTFO DSR 78.3 82.3 79.7 75.3 88.0 PAV DSR 20.3 22.0 22.7 25.3 26.3 BBR Stiffness -27.9 -28.0 -26.9 -26.8 -27.3 BBR m-value -27.7 -28.0 -27.3 -26.0 -26.4 DTT -26.1 -23.7 -22.4 -21.0 -22.7 True Grade - BBR 78.3 -27.7 81.5 -28.0 79.7 -26.9 86.3 -26.0 88.0 -26.4 True Grade - DTT 78.3 -26.1 81.5 -23.7 79.7 -22.4 86.3 -21.0 88.0 -22.7 C Original DSR 77.8 79.3 85.3 80.0 91.3 Phase Angle @ 70°C 62.4 64.0 63.6 63.3 57.2 RTFO DSR 75.1 76.2 76.6 77.9 79.5 PAV DSR 6.7 6.7 9.0 7.0 12.6 BBR Stiffness -39.6 -39.0 -41.0 -42.7 -41.0 BBR m-value -38.9 -38.1 -38.1 -40.3 -38.1 DTT -34.9 -36.8 -36.1 -37.7 -28.2 True Grade - BBR 75.1 -38.9 76.2 -38.1 76.6 -38.1 77.9 -40.3 79.5 -38.1 True Grade - DTT 75.1 -34.9 76.2 -36.8 76.6 -36.1 77.9 -37.7 79.5 -28.2 I Original DSR 71.8 77.3 76.5 81.9 84.6 Phase Angle @ 70°C 80.2 78.2 77.8 74.8 73.4 RTFO DSR 74.8 78.3 79.9 80.6 83.9 PAV DSR 17.5 20.1 18.9 22.1 22.6 BBR Stiffness -34.8 -33.9 -39.0 -30.8 -35.9 BBR m-value -29.2 -28.3 -27.8 -28.0 -23.3 DTT -25.8 -27.0 -25.4 -23.8 -23.2 True Grade - BBR 71.8 -29.2 77.3 -28.3 76.5 -27.8 80.6 -28.0 83.9 -23.3 True Grade - DTT 71.8 -25.8 77.3 -27.0 76.5 -25.4 80.6 -23.8 83.9 -23.2 ° Table 14. Results of grading of binders before and after SEP testing.

39 B Original DSR 69.3 72.8 72.6 74.4 75.7 Phase Angle @ 64°C 71.8 68.7 68.9 67.1 65.6 RTFO DSR 69.8 71.1 71.6 72.4 74.5 PAV DSR 10.4 10.9 10.9 11.1 12.4 BBR Stiffness -37.3 -37.8 -38.5 -38.5 -38.3 BBR m-value -37.9 -37.7 -36.5 -36.2 -36.6 DTT -34.1 -34.9 -35.1 -33.0 -34.1 True Grade - BBR 69.3 -37.3 71.1 -37.7 71.6 -36.5 72.4 -36.2 74.5 -36.6 True Grade - DTT 69.3 -34.1 71.1 -34.9 71.6 -35.1 72.4 -33.0 74.5 -34.1 F Original DSR 68.4 71.6 72.4 74.3 73.6 Phase Angle @ 64°C 83.5 85.4 85.2 83.6 83.6 RTFO DSR 67.8 70.2 71.1 76.5 74.3 PAV DSR 30.5 31.5 25.4 26.0 33.1 BBR Stiffness -24.9 -23.4 -24.0 -23.6 -23.9 BBR m-value -23.5 -22.8 -22.7 -25.0 -22.2 DTT -21.3 -18.7 -18.2 -15.9 -18.5 True Grade - BBR 67.8 -23.5 70.2 -22.8 71.1 -22.7 74.3 -14.1 73.6 -22.2 True Grade - DTT 67.8 -21.3 70.2 -18.7 71.1 -18.2 74.3 -15.9 73.6 -18.5 O Original DSR 65.6 69.1 70.2 74.1 76.0 Phase Angle @ 64°C 79.2 83.5 82.9 80.3 78.8 RTFO DSR 68.2 70.5 71.0 73.6 77.7 PAV DSR 19.2 20.1 20.6 20.2 22.1 BBR Stiffness -29.7 -27.9 -28.0 -27.7 -27.3 BBR m-value -30.1 -27.5 -27.5 -27.5 -26.8 DTT -30.2 -23.8 -23.6 -22.8 -22.0 True Grade - BBR 65.6 -29.7 69.1 -27.5 70.2 -27.5 73.6 -27.5 76.0 -26.8 True Grade - DTT 65.6 -30.2 69.1 -23.8 70.2 -23.6 73.6 -22.8 76.0 -22.0 K Original DSR 66.1 68.9 69.8 70.8 71.3 Phase Angle @ 64°C 89.1 88.0 86.7 88.1 88.3 RTFO DSR 65.3 67.1 67.3 68.3 69.9 PAV DSR 32.4 32.1 32.2 32.3 33.7 BBR Stiffness -13.0 -11.6 -13.8 -11.7 -11.0 BBR m-value -15.8 -15.8 -15.8 -15.0 -14.1 DTT -14.5 -9.0 -12.0 -10.9 -11.5 True Grade - BBR 65.3 -13.0 67.1 -11.6 67.3 -13.8 68.3 -11.7 69.9 -11.0 True Grade - DTT 65.3 -14.5 67.1 -9.0 67.3 -12.0 68.3 -10.9 69.9 -11.5 J Original DSR 64.3 69.1 71.6 72.0 74.8 Phase Angle @ 64°C 89.4 86.9 88.4 88.2 86.6 RTFO DSR 64.7 69.2 69.4 71.2 72.4 PAV DSR 27.0 31.1 27.9 29.1 30.0 BBR Stiffness -21.2 -19.0 -23.9 -22.2 -29.8 BBR m-value -20.7 -19.7 -21.2 -20.5 -19.5 DTT -21.0 -14.3 -14.5 -13.6 -13.4 True Grade - BBR 64.3 -20.7 69.1 -19.0 69.4 -21.2 71.2 -20.5 72.4 -19.5 True Grade - DTT 64.3 -21.0 69.1 -14.3 69.4 -14.5 71.2 -13.6 72.4 -13.4 E Original DSR 63.2 62.8 63.4 66.0 69.5 Phase Angle @ 58°C 83.0 82.7 82.4 81.1 78.6 RTFO DSR 60.9 63.9 65.6 65.9 71.3 PAV DSR 13.2 13.0 12.7 14.9 14.3 BBR Stiffness -36.7 -35.2 -35.1 -34.8 -35.0 BBR m-value -33.1 -35.2 -32.5 -34.4 -31.2 DTT -34.7 -30.6 -29.4 -30.0 -29.2 True Grade - BBR 60.9 -33.1 62.8 -32.5 63.4 -32.5 65.9 -34.4 69.5 -31.2 True Grade - DTT 60.9 -34.7 62.8 -30.6 63.4 -29.4 65.9 -30.0 69.5 -29.2 D Original DSR 60.3 62.4 64.8 65.2 67.6 Phase Angle @ 58°C 86.7 85.5 84.3 84.0 83.1 RTFO DSR 61.5 62.7 63.2 64.7 65.9 PAV DSR 15.5 15.2 14.8 15.1 15.1 BBR Stiffness -31.7 -32.3 -31.8 -32.4 -31.1 BBR m-value -32.5 -33.1 -29.6 -31.9 -32.7 DTT -26.0 -29.2 -29.4 -29.0 -28.7 True Grade - BBR 60.3 -31.7 62.4 -32.3 63.2 -29.6 64.7 -31.9 65.9 -31.1 True Grade - DTT 60.3 -26.0 62.4 -29.2 63.2 -29.4 64.7 -29.0 65.9 -28.7 Table 14. (Continued).

40 Binder ID Temp, oC 100 Pa Stress 3200 Pa Stress Unaged 130 150 170 190 Unaged 130 150 170 190 M 58 0.0500 0.0474 0.3260 0.1727 0.0801 0.1000 0.1385 0.1326 0.1034 0.0685 64 0.0790 0.0906 0.1581 0.3835 0.0677 0.3200 0.2146 0.4109 0.3815 0.1955 70 0.1200 0.2653 0.5203 0.7644 0.4954 1.1600 0.9883 1.2364 1.0724 0.7160 76 0.1900 1.2122 2.9427 1.8101 0.8002 4.3400 3.5709 3.7888 3.2963 2.2566 N 58 0.0700 0.1168 0.0626 0.0898 0.0830 0.1000 0.1721 0.1075 0.0752 0.0650 64 0.1400 0.2719 0.1100 0.2053 0.4125 0.2600 0.4889 0.2553 0.2035 0.2313 70 0.3200 1.6612 0.4064 0.1997 1.8000 0.8100 3.2819 0.5446 0.4046 0.9200 76 0.6400 1.3371 0.1698 1.2114 3.8847 2.5100 4.2000 3.4903 1.0648 2.3238 G 58 0.1212 0.6695 0.9805 0.1026 0.0795 0.1380 0.1643 0.2130 0.0738 0.0892 64 0.2216 0.2820 0.4007 0.2440 0.0710 0.2766 0.2127 0.3105 0.2366 0.1446 70 0.3761 0.4049 0.6539 0.5106 0.5207 0.5261 0.5818 0.7040 0.4514 0.4505 76 0.6632 1.5013 0.9277 0.7518 0.6698 1.3357 1.2024 1.8758 1.3503 0.9594 H 58 0.4600 0.6478 0.4793 0.2325 0.2693 0.5900 0.3988 0.2392 0.2360 0.2935 64 1.0500 1.0481 1.0372 0.5652 0.8394 1.5800 0.8867 0.7175 0.6685 0.5154 70 2.6800 0.6555 2.2746 1.5635 0.7825 4.5700 2.2220 1.7273 2.0313 1.1710 76 5.7200 3.8550 4.2959 3.4807 2.0714 10.4800 5.4825 5.1347 5.2013 3.2522 C 58 1.0137 0.9253 0.3740 0.2232 0.2759 1.0075 0.5853 0.3754 0.3605 0.2803 64 0.3326 1.2603 0.7737 0.9677 0.4490 1.7533 1.3344 1.1739 1.8443 0.7928 70 0.3690 2.8768 2.1784 2.2559 1.8240 5.5538 4.8275 3.5356 3.9806 2.5025 76 5.4942 7.1843 4.3437 4.5098 2.7163 13.2738 12.5172 7.7141 11.6331 7.5678 I 58 2.4612 1.2553 1.0379 0.5284 0.0386 2.8189 1.0503 1.2532 0.7221 0.4895 64 3.6981 2.2093 1.6739 0.9204 0.1364 5.8972 2.9856 2.5595 1.6446 1.4043 70 14.5110 4.8845 4.4979 2.8155 1.7774 15.4491 7.3369 7.4084 4.8200 2.9999 76 17.6200 11.6020 6.4407 1.7802 9.4055 27.6559 16.3003 14.7119 8.3325 10.0338 B 58 1.1572 1.4219 0.2614 0.7081 0.6351 2.3519 0.9589 0.7046 0.7697 0.7519 64 2.5669 0.3968 0.9438 1.2274 1.5359 6.6602 2.7654 2.6778 1.8109 2.3599 70 6.4338 1.5680 2.0909 3.5332 3.8034 16.4549 6.7619 5.0541 5.5288 6.5341 76 18.4670 3.5533 6.7418 5.7535 0.3094 34.8406 12.4888 11.9631 10.7913 11.4966 F 58 2.9939 1.1228 2.2369 1.5380 2.1366 3.5428 2.7608 2.7867 2.5458 2.5664 64 7.1896 6.1727 5.6663 3.7491 4.5189 8.6328 7.5444 6.9656 6.0781 5.8350 70 15.5393 13.3200 12.2410 9.0157 10.6770 18.7640 16.4963 15.0584 12.9425 13.4653 76 32.0430 27.0610 24.8970 23.0810 23.8840 38.9281 33.0313 30.3894 30.4113 27.9788 O 58 6.0360 3.5217 2.8005 1.1717 0.4555 5.6938 4.5128 3.6350 2.3061 1.9970 64 10.3100 7.2912 2.4976 2.9879 2.0882 12.2366 10.3097 7.4744 5.7025 4.6595 70 21.7490 14.6570 12.8270 8.1640 2.7960 28.1559 22.5944 17.2275 13.2616 11.6398 76 27.2230 27.5810 24.8370 18.0570 8.1853 40.2125 41.9750 32.6094 25.0438 19.3758 K 58 4.8934 3.6084 1.8297 0.4587 1.6453 5.7784 4.4663 4.2838 3.3775 2.6775 64 10.9300 5.4157 4.8001 6.5832 3.4524 12.1772 9.5750 9.9984 9.2616 6.8888 70 22.3350 17.0770 16.5430 15.0000 13.2470 32.8875 24.7503 24.4169 21.0691 17.9931 76 35.2620 41.5150 34.8630 13.1870 14.8320 59.6625 53.2031 53.8750 38.6406 35.0313 J 58 5.4921 3.5265 2.7391 2.4878 0.7402 6.2943 4.5581 4.0203 3.3891 3.2017 64 13.8943 7.1120 6.4143 4.6326 0.6629 16.1071 10.9047 7.8103 7.3150 7.2913 70 29.3687 19.7640 11.8350 10.7630 9.2671 34.1458 26.0844 19.8675 16.7050 14.5859 76 58.7047 39.6080 12.1270 25.2900 16.7150 67.6948 51.0125 40.7594 36.2156 35.7234 E 58 11.3737 7.9921 3.0642 4.3426 2.2957 14.3829 10.7188 7.8388 8.2328 3.9384 64 23.5373 16.9930 13.4830 6.4829 4.7986 29.4433 22.8119 18.1700 15.7816 8.7728 70 46.0083 21.6180 22.2620 16.4600 9.0460 57.6240 47.0094 39.0000 27.7828 19.0259 76 92.1573 79.8670 64.1290 38.6380 28.6420 114.3906 92.6563 75.8344 56.0125 39.7531 D 58 10.1716 3.7658 6.0801 4.0700 4.9074 12.1819 8.7575 8.5525 7.0372 6.3491 64 22.0473 14.0720 10.7090 11.4250 9.5916 26.5592 19.2153 18.1231 12.6216 14.0603 70 44.5693 32.5280 23.3700 12.6540 17.1720 53.3438 41.9750 40.8813 30.4881 26.8969 76 83.0037 34.6660 48.3080 47.1410 40.3310 99.6958 45.4875 74.5125 63.8688 56.8281 Table 15. Summary of non-recoverable creep compliance (Jnr, 1/Pa) results from the MSCR tests.

41 Binder H, 3200 Pa Stress 0 2 4 6 8 10 12 14 16 18 20 52 58 64 70 76 82 Temperature (C) Jn r (1 /P a) Unaged SEP 130 SEP 150 SEP 170 SEP 190 Figure 21. Plot of Jnr for modified Binder H from MSCR tests. Binder E, 3200 Pa Stress 0 10 20 30 40 50 60 70 80 90 100 52 58 64 70 76 82 Temperature (C) Jn r (1 /P a) Unaged SEP 130 SEP 150 SEP 170 SEP 190 Figure 22. Plot of Jnr for unmodified Binder E from MSCR tests.

low temperature degradation due to exposure to higher tem- peratures for most binders. Table 18 shows the change in phase angle as measured in PG grading of the binders. These data show that generally, phase angles tend to decrease with increasing SEP temperatures for both modified and unmodified binders. However, a few binders had unusual results. Binders C, F, and O exhibited an initial increase in phase angle at an SEP temperature of 130°C, then decreased with higher SEP temperatures. A decrease in phase angle indicates that the binders became stiffer and more elastic after they were exposed to higher temperatures. As observed by Airey and Brown (28), had the polymers in the modified binders been damaged by the increased tempera- tures, the phase angles should have increased, indicating a loss of elastic behavior. Therefore, the phase angle data indicates that there are no signs of polymer degradation in the binders. Figure 23 shows the effect of SEP temperature on non- recoverable creep compliance, Jnr, for the unmodified binders. The data shown in this graph are from the binder high grade temperatures and a stress level of 3200 Pa. The trend evident from this chart is that the non-recoverable compliance val- ues decrease with higher SEP temperatures. Conversely, the 42 Binder ID True Grade SEP Temperature (°C) 130 150 170 190 M 85.5 -19.5 3.0 4.2 5.4 6.8 N 84.3 -25.5 -1.3 1.4 4.6 6.7 G 82.5 -24.2 7.4 5.4 6.2 7.3 H 78.3 -26.1 3.2 1.4 8.0 9.7 C 75.1 -38.7 1.1 1.5 2.8 4.4 I 71.8 -29.2 5.5 4.7 8.8 12.1 B 69.3 -37.3 1.8 2.3 3.1 5.2 F 67.8 -21.3 2.4 3.3 6.5 5.8 O 65.6 -29.7 3.5 4.6 8.0 10.4 K 65.3 -13.0 1.8 2.0 3.0 4.6 J 64.3 -20.7 4.8 5.1 6.9 8.1 E 60.9 -33.1 1.9 2.5 5.0 8.6 D 60.3 -31.7 2.1 2.9 4.4 5.6 Avg. of Modified Binders 2.5 2.7 5.0 6.7 Avg. of Unmodified Binders 3.1 3.6 6.1 7.9 Binder ID True Grade SEP Temperature (°C) 130 150 170 190 M 85.5 -19.5 1.8 3.1 2.2 2.2 N 84.3 -25.5 7.1 5.2 5.0 6.0 G 82.5 -24.2 0.3 1.9 0.7 3.0 H 78.3 -26.1 2.4 3.7 5.1 3.4 C 75.1 -38.7 2.1 2.8 1.2 0.8 I 71.8 -29.2 2.2 3.8 5.4 6.0 B 69.3 -37.3 -0.4 0.8 1.1 0.7 F 67.8 -21.3 2.6 3.1 5.4 2.8 O 65.6 -29.7 5.9 6.1 6.9 7.7 K 65.3 -13.0 5.5 2.5 3.6 3.0 J 64.3 -20.7 6.7 6.5 7.4 7.6 E 60.9 -33.1 2.5 3.7 3.1 3.9 D 60.3 -31.7 2.5 2.3 2.7 3.0 Avg. of Modified Binders 2.9 2.2 2.7 2.6 Avg. of Unmodified Binders 4.0 4.0 4.9 4.9 Table 16. Changes to high temperature grade (°C) after SEP test. Table 17. Changes to low temperature grade (°C) after SEP test. Binder ID True Grade SEP Temperature (°C) 130 150 170 190 M 85.5 -19.5 -1.73 -0.62 0.05 -3.34 N 84.3 -25.5 -0.40 1.40 -3.50 -3.90 G 82.5 -24.2 -3.07 -3.76 -5.32 -4.02 H 78.3 -26.1 -2.10 -3.83 -4.57 -5.54 C 75.1 -38.7 1.66 1.18 0.97 -5.21 I 71.8 -29.2 -2.03 -2.44 -5.43 -6.80 B 69.3 -37.3 -3.18 -2.93 -4.73 -6.22 F 67.8 -21.3 1.89 1.70 0.12 0.13 O 65.6 -29.7 4.29 3.67 1.06 -0.42 K 65.3 -13.0 -1.06 -2.40 -1.03 -0.84 J 64.3 -20.7 -2.50 -1.00 -1.20 -2.80 E 60.9 -33.1 -0.31 -0.58 -1.96 -4.45 D 60.3 -31.7 -1.23 -2.35 -2.68 -3.57 Avg. of Modified Binders -1.5 -1.4 -2.9 -4.7 Avg. of Unmodified Binders -0.1 -0.5 -1.6 -2.7 Table 18. Changes to Phase Angle (degrees) after SEP tests. 0 130 150 170 190 J K D F E I O 0 2 4 6 8 10 12 14 16 18 Jnr (1/Pa) SEP Temp. (C) Binder ID Figure 23. MSCR Jnr results at 3200 Pa stress for unmodified binders.

binders exhibit more recoverable strain (i.e., are more elastic) after exposure to higher temperatures. The unmodified binder that has the greatest change in Jnr with higher SEP temper- atures is Binder I, the air-blown PG 70-28 using an Alaskan Slope/Canadian crude blend. This binder was consistently among the binders with the greatest property changes due to the SEP conditioning. It was also the binder with the highest opacity and, therefore, it may have lost some volatile compo- nents that caused a substantial increase in stiffness. Figure 24 shows the effect of SEP temperature on Jnr for modified binders. As with the unmodified binders, the Jnr data used to evaluate degradation were from the high grade temper- ature, except for the PG 82 binders (M, N, and G). For these three binders, the creep recovery tests were not performed at 82°C, so the data shown is from the test temperature of 76°C. This graph is shown with the same Jnr scale as for the un- modified binders to illustrate the lower compliance results for the modified binders. As with the unmodified binders, the modified binders show a trend of decreasing Jnr as the SEP temperature was increased. However, there is no evidence of degradation of the binders due to the exposure to the elevated temperatures in the SEP test. In summary, the assessment of changes in binder proper- ties due to the conditioning of the samples to elevated tem- peratures in the SEP test indicates that all binders increase in stiffness with higher temperatures. The magnitudes of the property changes differ among the binders in the experiment, but with the limited data set there does not appear to be any consistent trend that binders from particular crude sources are more temperature susceptible than others. Also, modified and unmodified binders generally appear to be affected by high temperatures to similar magnitudes. The results do not provide any evidence that high temperatures cause degrada- tion of the binders. However, this finding may only indicate that the conditions of the SEP test are not severe enough to cause significant damage to the binders. Mixture Testing This section presents the results of the tests with the binders in mixture tests over a range of mixing and compaction tem- peratures. Results are given for the coating tests, the workabil- ity tests, the compaction tests, and the indirect tensile creep compliance and strength tests. Mixture Coating Tests Results of the coating tests are summarized in Table 19. The table shows the percentage of coated particles determined 43 0 130 150 170 190 H B C M N G 0 2 4 6 8 10 12 14 16 18 Jnr (1/Pa) SEP Temp. (C) Binder ID Figure 24. MSCR Jnr results at 3200 Pa stress for modified binders. Percentage of Coated Aggregate Particles by ASTM D2489 Mixer Type Pugmill Bucket Mixing Temp. °C 120 140 160 180 120 140 160 180 Mixing Temp. °F 248 284 320 356 248 284 320 356 M 85.5 -19.5 52.6 59.0 90.1 89.6 63.0 98.0 99.3 99.3 N 84.3 -25.5 21.5 60.7 68.2 88.3 57.3 70.9 90.4 99.5 G 82.5 -24.2 19.5 65.4 83.3 82.1 79.6 91.4 93.9 97.4 H 78.3 -26.1 37.4 74.8 91.7 83.0 73.0 94.5 88.5 92.9 C 75.1 -38.7 40.8 74.9 85.3 86.4 81.0 88.4 92.5 96.0 I 71.8 -29.2 53.1 72.3 87.1 91.7 83.6 98.2 99.2 100 B 69.3 -37.3 72.4 71.9 82.5 87.2 82.2 95.9 99.4 98.9 F 67.8 -21.3 51.9 89.3 88.0 90.3 77.3 98.2 99.0 99.4 O 65.6 -29.7 57.2 83.9 86.5 92.0 90.1 89.2 99.8 99.7 K 65.3 -13.0 81.0 87.7 90.7 95.5 78.5 96.7 99.9 99.9 J 64.3 -20.7 81.8 83.8 90.3 92.1 75.0 96.4 99.1 99.9 E 60.9 -33.1 91.2 86.7 92.5 95.9 85.6 97.8 98.4 100 D 60.3 -31.7 89.4 91.2 95.0 98.1 91.0 97.3 99.2 99.6 Table 19. Summary of coating test results.

44 Factor Type Levels Values Binder fixed 13 B,C,D,E,F,G,H,I,J,K,M,N,O Temp fixed 4 120,140,160,180 Mixer fixed 2 Bucket,Pugmill Analysis of Variance for %Coating, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder 12 9507.79 10437.15 869.76 39.04 0.000 Temp 3 23859.07 23195.39 7731.80 347.06 0.000 Mixer 1 10341.81 9827.25 9827.25 441.12 0.000 Binder*Temp 36 5421.71 5917.35 164.37 7.38 0.000 Binder*Mixer 12 2627.86 2565.34 213.78 9.60 0.000 Temp*Mixer 3 1287.80 1159.38 386.46 17.35 0.000 Binder*Temp*Mixer 36 4483.41 4483.41 124.54 5.59 0.000 Error 118 2628.77 2628.77 22.28 Total 221 60158.22 Table 20. ANOVA results for mix coating experiment. ONMKJIHGFEDCB 90 80 70 180160140120 PugmillBucket 90 80 70 Binder M ea n Temp Mixer Main Effects Plot for %Coating Fitted Means Modified binders are shown with triangle symbols Figure 25. Effects of binder, temperature, and mixer on coating percentage. by the Ross count method as mixing temperatures were increased from 248°F to 356°F (120°C to 180°C). Analysis of variance (ANOVA) is a common method of analyzing data from a statistical experimental design to assess differences associated with experimental treatments. Out- put from the ANOVA for the coating experiment is shown in Table 20. From these results, it can be seen that all three of the main factors (binder ID, mixing temperature, and mixer type) were highly significant. The interactions of these factors were also statistically significant, however, based on the F values, not nearly to the same degree as the main factors by themselves. The main effects plots for the coating test experiment are shown in Figure 25. All of the modified binders, except Binder B, plot below the overall mean for percent coating, which indicates that aggregates are harder to coat with the modified binders under the same conditions. The tempera- ture effect on coating percentage follows the expected trend of increased coating at higher temperatures, but that the effect is not linear. The results also show that the bucket mixer provided better coating than the pugmill. This seems to conflict with the hypothesis that the bucket mixer would be less efficient than the pugmill due to its lower mixing speed (slower shear rate). However, besides mixing speed, the action of the two mixers is very different. The tumbling action of the bucket mixer, like that of a drum mix plant, allows aggregate particles to stay in contact with the binder and other coated particles. This could be a more efficient coating process than a pugmill, which is a more violent churning action with aggregate particles tossed into space, especially when the pug- mill is under filled. For each binder, the coating percentages were related to mixing temperatures using Sigmoid functions of the form: C ae bT = + − 1 1 8( )

where C is the percentage coating at any temperature T, and a and b are regression constants. Regression results for each binder are summarized in Table 21. The relationships were used to estimate the coating percentage of the binders at any temper- ature. The equiviscous mixing temperatures for the unmodified binders were used to establish reference coating percentages for the bucket mixer and the pugmill mixers. These reference coating percentages were 98% (bucket) and 89% (pugmill mixer). The temperatures to achieve these coating percent- ages for each binder were then estimated with the Sigmoid function regression equations. These predicted mixing tem- peratures for equivalent coating are included in Table 21. It is evident from these results that the predicted tempera- tures from the two laboratory mixers are different and neither consistently provides reasonable mixing temperatures. With the bucket mixer, the temperature to achieve the baseline coating percentage for Binder H was 412°F (211°C). This result is much higher than most asphalt technologists con- sider reasonable. At the other extreme, the lowest predicted temperature to achieve the baseline coating percentage was for Binder I, which is not consistent with the rank of the binder grades. Binder M, modified with SBS and Sasobit®, is somewhat lower than the other highly modified binders, but this may be due to the beneficial effect of the Fischer Tropsch wax. For the pugmill mixer, the predicted temperature for modified Binder B is excessive, and the temperatures for the lowest-graded binders, D and E, are lower than expected. Overall, the inconsistent coating test results for several binders demonstrate the challenge of using this method to predict mixing temperatures and to use this approach to validate the candidate methods. Mixture Coating Tests with Incompletely Dried Aggregate A second small coating experiment was conducted to assess the effect of residual aggregate moisture on the coating of the aggregates with four binders. One of the challenges with this limited experiment was preparing the samples with residual moisture to specific mixing temperatures. The gran- ite aggregate used in this experiment had a low water absorp- tion (0.7%) and although the coarse aggregates were saturated at the start of the final heating step by combining with hot, dry fine aggregate and using a blow torch, the amount of moisture remaining in the aggregate at the time the asphalt was added had certainly decreased substantially. A paired t-test was used to compare the results of the coating test with and without incompletely dried aggregates. The exper- imental hypothesis was that the coating percentages were the same (difference = 0) for partially wet and dry aggregates. The results, provided in Table 22, show that there is a high prob- ability (P-value = 0.469) that the coating percentages of dry samples and incompletely dry samples were not statistically different. Some asphalt technologists have suggested that 45 ID True Grade Bucket Mixer Pugmill Mixer a b T for 98% Coating °F (°C) a b T for 89% Coating °F (°C) M 85.5-19.5 24590795 0.146 289 (143) 117 0.039 345 (174) N 84.3-25.5 3518845 0.113 334 (168) 1911 0.053 361 (183) G 82.5-24.2 146 0.051 347 (175) 8990 0.067 333 (167) H 78.3-26.1 14 0.031 412 (211) 3183 0.064 318 (159) C 75.1-38.7 30688 0.078 360 (182) 876 0.055 324 (162) I 71.8-29.2 134998 0.112 284 (140) 130 0.042 333 (167) B 69.3-37.3 3514 0.081 300 (149) 7 0.021 374 (190) F 67.8-21.3 715 0.066 318 (159) 2902 0.068 298 (148) O 65.6-29.7 404 0.056 347 (175) 130 0.044 318 (159) K 65.3-13.0 58144 0.102 293 (175) 4 0.024 297 (147) J 64.3-20.7 131832 0.107 295 (146) 2 0.017 318 (159) E 60.9-33.1 9177 0.091 289 (143) 0.4 0.010 222 (106) D 60.3-31.7 182 0.063 293 (145) 2 0.023 250 (121) Table 21. Coating test regression model results. Paired T for Wet %Coated - Dry %Coated N Mean St Dev SE Mean Wet %Coated 32 66.0219 27.8339 4.9204 Dry %Coated 32 63.0844 31.3435 5.5408 Difference 32 2.93750 22.66805 4.00718 95% CI for mean difference: (–5.23520, 11.11020) T-Test of mean difference = 0 (vs not = 0): T-Value = 0.73 P-Value = 0.469 Table 22. Results of paired T-test for %coating using wet and dry aggregates.

moisture escaping from aggregate pores during mixing with binder may cause the asphalt film to foam and significantly expand, which would enhance the coating process. Although steam was evident during the mixing, foaming of the asphalt was not observed during the tests with the incompletely dried aggregates. Workability Tests The raw torque data from each workability test was processed and a least-squares regression was used to fit a quadratic equation to the processed torque versus temperature data. The temperature-torque regressions for each replicate sample are shown in Table 23. Initially, a reference torque based on the midpoints between the equiviscous mixing and compaction temperatures of the unmodified binders was considered. This yielded a reference torque value of 9.7 N-m. However, results with some modified binders did not quite reach this value even at the highest temperature. One of the challenges with analysis of the workability data was finding a single torque value to use as a reference point for comparing the binders. In the tempera- ture range that the workability tests span, typically from about 180°C to 120°C, the results for all binders did not cross any given torque value, which required an extrapolation for some results beyond the experimental range. 10 N-m was selected as a reasonable reference torque value because it was close to the average equiviscous midpoint torque and required small extrapolations. Therefore, using the temperature-torque regressions, the temperatures at which the binder-sand mix- ture reached 10 N-m of torque were determined. These results also are summarized in Table 23. It can be seen that for over half of the binders tested, the difference between replicates was more than 25°F. Some samples had very shallow temperature- torque relationships, which meant that the torque only changed by a relatively small amount over a wide temperature range. Replicate results that had similar but shallow and nearly parallel temperature-torque regressions had large differences between the temperatures to reach the reference torque value. 46 ID Run Regression Equation R2 ºC ºF ºF Avg. M 1 y = 0.0035x2 - 1.2027x + 111.88 0.67 152 305 328 2 y = 0.0045x2 - 1.5717x + 147.32 0.80 177 351 N 1 y = 0.0044x2 - 1.4866x + 135.3 0.63 177 351 347 2 y = 0.0032x2 - 1.1296x + 110.27 0.50 173 343 G 1* y = 0.0135x2 - 4.2228x + 339.19 0.39 134 272 289 2 y = 0.0046x2 -1.554x + 139.94 0.89 152 306 H 1 y = 0.002x2 - 0.834x + 95.567 0.89 182 360 358 2 y = 0.0041x2 - 1.5494x + 158.01 0.96 180 356 C 1 y= 0.0021x2 - 0.8114x + 88.106 0.61 181 358 352 2 y = 0.0012x2 - 0.5356x + 67.004 0.56 175 347 I 1 y = 0.0039x2 - 1.3958x + 136.84 0.74 180 356 361 2 y = 0.0029x2 - 1.1313x + 120.13 0.75 186 367 B 1 y = 0.0018x2 - 0.6268x + 62.533 0.23 141 285 307 2 y = 0.0011x2 - 0.3908x + 44.778 0.19 165 328 F 1 y = 0.0019x2 - 0.6247x + 60.037 0.59 138 280 295 2 y = 0.002x2 - 0.7276x + 74.616 0.59 154 309 O 1 y = 0.0027x2 - 0.8801x + 78.499 0.51 129 263 251 2 y = 0.0021x2 - 0.6556x + 57.564 0.15 115 238 K 1 y = 0.001x2 - 0.3593x + 37.633 0.39 112 233 257 2 y = 0.0013x2 - 0.4528x + 47.712 0.56 138 280 J 1 y = 0.0028x2 - 0.927x + 82.634 0.64 128 262 257 2 y = 0.0016x2 - 0.5354x + 51.654 0.47 123 253 E 1 y = 0.0001x2 - 0.1246x + 25.015 0.42 135 275 294 2 y = 0.002x2 - 0.7656x + 80.762 0.78 156 313 D 1 y = 0.001x2 - 0.4073x + 47.171 0.47 138 280 305 2 y = 0.002x2 - 0.6858x + 68.707 0.46 165 329 * Incomplete data set. Table 23. Workability experiment — temperatures to yield equivalent torque.

Unfortunately, the poor repeatability and the low R2 for sev- eral of the regressions indicate that this test may not be a dependable test to evaluate specific relationships between temperature and workability for binders. Another way to analyze the workability results was to com- pare the torque values at specific temperatures. Figure 26 through Figure 28 show a series of plots of torque values cal- culated at three temperatures spanning 40°C (72°F). Although the differences in torque values between replicates are evident, relative to the range of torque values among the binders, the replicate differences are in the order of 10% to 15%. The aver- age difference between replicates at 125°C is 2.2 N-m, and the range in torque among the different binders is 20 N-m. At 165°C, the average difference between replicates is 1.3 N-m with an overall range of about 9 N-m. It also can be seen from these plots that the second run yielded higher torque results for most binders. The procedure was reviewed to determine whether the second sample was aged longer and stiffened in the oven before testing. Each replicate sample was individually mixed and placed in the oven until it reached 180°C to start the workability test. The systematic pattern that caused the second sample to be less workable could have been due to a longer time in the oven for the second sample due to opening the oven to retrieve the first sample and the workability bowl and paddle. The one binder that does not follow that trend was Binder O. This was the only case where the second sample was run on a different day from the first sample. In this review, it was discovered that the data for the first sample for Binder G was incomplete: data was only recorded from about 165°C to 135°C. Therefore results for this replicate were excluded in the analyses. Compaction Tests The mix compaction experiments were conducted to assess the effect of compaction temperature on the com- pacted specimen density and resistance to compaction based on the maximum shear ratio obtained from the specially equipped Pine Instruments SGC, model AFG1A. In order to better differentiate the binder stiffness effects (i.e., binder ID 47 5 10 15 20 25 30 B C D E F G H I J K M N O To rq ue @ 1 25 °C Run 1 Run 2 Figure 26. Torque calculated at 125°C from workability test results. 5 10 15 20 25 30 B C D E F G H I J K M N O To rq ue @ 14 5° C Run 1 Run 2 Figure 27. Torque calculated at 145°C from workability test results.

and temperatures), the specimens were compacted to only 25 gyrations. A summary of the main compaction experiment is shown in Table 24. Table 25 provides the Minitab ANOVA output for rela- tive density, %Gmm, as the dependent variable. The main effects (binder and compaction temperature) were statisti- cally significant (P-value <0.05). Surprisingly however, the ANOVA results indicate that the interaction of the main effects was not significant (P-value >0.05). This suggests that within each binder set, increasing the compaction tem- perature did not have a statistically significant impact on the mixture density. 48 5 10 15 20 25 30 B C D E F G H I J K M N O To rq u e @ 16 5° C Run 1 Run 2 Figure 28. Torque calculated at 165°C from workability test results. %Gmm Max. Shear Ratio Comp. Temp. °C 110 130 150 170 110 130 150 170 Comp. Temp. °F 230 266 302 338 230 266 302 338 M 85.5 -19.5 92.5 92.7 92.7 93.1 0.912 0.881 0.888 0.888 N 84.3 -25.5 91.7 92.0 92.3 92.9 0.782 0.788 0.744 0.793 G 82.5 -24.2 91.6 92.1 92.5 93.0 0.848 0.888 0.872 0.906 H 78.3 -26.1 92.4 92.8 92.6 93.0 0.860 0.821 0.861 0.871 C 75.1 -38.7 92.3 92.4 93.5 93.1 0.852 0.823 0.827 0.875 I 71.8 -29.2 92.4 92.1 92.5 92.7 0.812 0.732 0.854 0.786 B 69.3 -37.3 92.6 93.0 93.1 93.3 0.819 0.883 0.827 0.908 F 67.8 -21.3 92.7 92.9 92.5 93.5 0.863 0.837 0.979 0.961 O 65.6 -29.7 92.7 93.1 93.3 93.3 0.820 0.800 0.936 0.942 K 65.3 -13.0 92.5 93.3 93.3 93.6 0.802 0.832 1.000 0.983 J 64.3 -20.7 92.2 92.5 92.4 92.8 0.852 0.843 0.889 0.790 E 60.9 -33.1 92.8 92.7 93.3 93.6 0.832 0.872 0.881 0.862 D 60.3 -31.7 92.7 93.0 93.2 93.2 0.821 0.830 0.837 0.873 Table 24. Summary of Compaction Experiment A results. Factor Type Levels Values Analysis of Variance for %Gmm, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 13 B,C,D,E,F,G,H,I,J,K,M,N,O Temperature fixed 4 230,266,302,338 Binder 12 9.80846 9.80846 0.81737 10.93 0.000 Temperature 3 8.11731 8.11731 2.70577 36.17 0.000 Binder*Temperature 36 3.57769 3.57769 0.09938 1.33 0.172 Error 52 3.89000 3.89000 0.07481 Total 103 25.39346 S = 0.273510 R-Sq = 84.68% R-Sq (adj) = 69.66% Table 25. ANOVA for relative density from Compaction Experiment A.

Figure 29 is a plot of the main effects that shows as com- paction temperature increased, the relative density increased for the relatively low compactive effort used in this experi- ment. The mean densities (averaged over all compaction temperatures) for each of the unmodified binders (D, E, F, J, K, and O) plot above the grand mean except for Binder J. This provides a level of confidence that binder stiffness or consis- tency has some effect on compacted density. Figure 30 summarizes a Tukey’s pair-wise comparison analy- sis of just the binder effect. This figure shows a cross matrix of the binders shown in rows and columns. Black cells identify binder pairs that had %Gmm results that were not statistically different. For example, the average density for Binder M (85.5- 19.5) was statistically different only with Binder N. This indi- cates that the warm asphalt additive Sasobit® used in Binder M improved the compactability of the mix compared to the sim- ilarly graded Binder N. Other comparisons associated with Binders H, C, and J were unexpected. Compacted density results for modified Binders H (78.8-26.1) and C (75.1-38.7) compared more favorably with most of the unmodified binders than with the other modified binders. On the other hand, unmodified Binder J (64.3-20.7) compared favorably with all of the modified binders and was statistically different than the two unmodified binders with the closest true grades, Binders O and K. As with the coating test results and the workability test results, there are several compaction test results that seem inconsistent with the binder grades. Unfortunately there does not appear to be a pattern with the inconsistencies attributed to certain binders. Linear regressions were established between %Gmm and compaction temperature for each binder. The regressions are shown in Table 26. Given that the equiviscous compaction 49 Figure 29. Main effects plot for %Gmm from Compaction Experiment A. ONMKJIHGFEDCB 93.2 93.0 92.8 92.6 92.4 92.2 338302266230 Binder M ea n Temperature Main Effects Plot for %Gmm Data Means Modified binders are shown with a triangle symbol M N G H C I B F O K J E D M 85.5-19.5 N 84.3-22.5 G 82.5-24.2 H 78.3-26.1 C 75.1-38.7 I 71.8-29.2 B 69.3-37.3 F 67.8-21.3 O 65.6-29.7 K 65.3-13.0 J 64.3-20.7 E 60.9-33.1 D 60.3-31.7 Figure 30. Matrix chart showing binder pairs that had statistically different compacted densities.

temperatures for unmodified binders are considered reason- able and satisfactory, they were used to establish a reference density. The relative density for the mixtures with the five unmodified binders at their respective equiviscous compaction temperatures ranged from 92.4 to 93.1%, with an average den- sity of 92.9 %Gmm. Using the linear regressions equations for each binder in Table 26, the compaction temperature to achieve 92.9 %Gmm was predicted for each binder. These results are also summarized in Table 26. These results are generally con- sistent with the binder grades with a few exceptions. The pre- dicted compaction temperature for Binder I is extremely high as a result of the low slope term in the regression. The R2 of the linear regression for this binder was not as good as for most other binders, and the predicted temperature is well outside of the experimental range of the data. The predicted compaction temperature for Binder J is also very high, considering that it is an unmodified binder. Another output of the main compaction experiment was the maximum shear ratio developed during the compaction process. According to Pine Instrument Company (52), maxi- mum shear ratio is a parameter that indicates the resistance of the mixture to compaction as measured with the specially equipped AFG1 Pine SGC. The ANOVA results with shear ratio as the dependent variable are shown in Table 27. This analysis also shows that the main factors, binder and com- paction temperature, as well as their interaction are statisti- cally significant. However, the main effects and interactions plots, shown in Figure 31 and Figure 32, do not follow any rea- sonable trends for individual binders such as decreasing shear ratio with increasing compaction temperatures, or higher shear ratios for mixtures with modified binders compared with unmodified binders. For this reason, the maximum shear ratio does not appear to be a useful indicator of compactability. Compaction Experiment B was a 1⁄2 factorial experiment designed to evaluate the factors binder, temperature, aggregate, and gradation. Since binder and temperature effects were ana- lyzed in Compaction Experiment A, the factors of primary interest in this analysis were gradation (coarse versus fine) and 50 Table 26. Compaction experiment regressions. Table 27. ANOVA for maximum compaction shear ratio from Compaction Experiment A. ID True Grade Regression Equation (T is Temperature ºC) R 2 Compaction Temperature for 92.9%Gmm, ºF (ºC) M 85.5 -19.5 %Gmm = 0.0087T + 91.527 0.75 317 (159) N 84.3 -25.5 %Gmm = 0.0193T + 89.510 0.85 349 (176) G 82.5 -24.2 %Gmm = 0.0228T + 89.085 0.78 334 (168) H 78.3 -26.1 %Gmm = 0.0085T + 91.495 0.47 331 (166) C 75.1 -38.7 %Gmm = 0.0182T + 90.260 0.59 293 (145) I 71.8 -29.2 %Gmm = 0.0066T + 91.496 0.30 417 (214) B 69.3 -37.3 %Gmm = 0.0119T + 91.319 0.65 272 (133) F 67.8 -21.3 %Gmm = 0.0098T + 91.508 0.27 289 (143) O 65.6 -29.7 %Gmm = 0.0098T + 91.718 0.44 284 (140) K 65.3 -13.0 %Gmm = 0.0151T + 91.060 0.54 257 (125) J 64.3 -20.7 %Gmm = 0.0098T + 91.097 0.57 354 (179) E 60.9 -33.1 %Gmm = 0.0140T + 91.119 0.71 262 (128) D 60.3 -31.7 %Gmm = 0.0085T + 91.852 0.51 264 (129) Factor Type Levels Values Analysis of Variance for Shear Ratio, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 13 B,C,D,E,F,G,H,I,J,K,M,N,O Temperature fixed 4 230,266,302,338 Binder 12 0.138555 0.131887 0.010991 10.83 0.000 Temperature 3 0.046824 0.047087 0.015696 15.46 0.000 Binder*Temperature 36 0.132823 0.132823 0.003690 3.63 0.000 Error 50 0.050751 0.050751 0.001015 Total 101 0.368952 S = 0.0318592 R-Sq = 86.24% R-Sq(adj) = 72.21%

51 Figure 31. Main effects plot for maximum shear ratio from Compaction Experiment A. Figure 32. Interaction plot for binder and temperature on maximum shear ratio. ONMKJIHGFEDCB 93.2 93.0 92.8 92.6 92.4 92.2 338302266230 Binder M ea n Temperature Main Effects Plot for %Gmm Data Means Modified binders are shown with a triangle symbol 338302266230 1.00 0.95 0.90 0.85 0.80 0.75 0.70 Temperature M ea n K M N O B C D E F G H I J Binder Interaction Plot for Shear Ratio Data Means Modified binders shown with open triangles and dashed lines aggregate type (low absorption and angular granite compared with a high absorption, more rounded gravel). In the experi- mental design, binder and temperature had four levels, and aggregate and gradation had two levels. Binder and tempera- ture were reduced to two 2-level factors for the design. This resulted in a 26 design, which was reduced to a 1⁄2 factorial, yielding 32 observations. Since the experiment was repli- cated, a total of 63 observations were made. The ANOVA table for this experiment is shown in Table 28. Due to the 1⁄2 fac- torial design, some of the interactions of the factors were sac- rificed. The ANOVA table shows the effects of the main effects and the two-way interactions. These results show that grada- tion has the largest affect on relative density, followed by aggre- gate type. Recall that each of these mixtures was, in effect, normalized by designing them with a single binder to 96% Gmm at 75 gyrations. These experimental results indicate that a mixture’s aggregate components (gradation, particle shapes, texture, absorption, etc.) have a greater affect on com- paction behavior than the binder characteristics. This finding is consistent with other research at NCAT (18). Although it has little significance to the primary objective of this project, data from the compaction experiments also made

it possible to assess the effect of RAP on the compactability of HMA in an SGC. This limited analysis examined the effects of three factors on the density (% of Gmm) of the compacted specimens at 25 gyrations. RAP content was the variable of pri- mary interest and was evaluated at two levels, 0 and 15%. Both mixtures used a fine-graded blend of granite aggregates. Two binders were also included in the analysis: B (64-34) and M (82-16). The third variable was compaction temper- ature, which was tested at four levels. The ANOVA on this data set is shown in Table 29. These results indicate that each of the main factors, including RAP content, have a statistically significant effect on the com- pactability of the mixtures. The interaction plot from this analysis is shown in Figure 33. This diagram shows that den- sities increased as compaction temperatures increased and also that the densities for the samples with the softer-grade Binder B were higher than the samples with the stiffer Binder M at equivalent temperatures. The right side of the interaction plot shows that the mixtures with 15% RAP had higher den- sities than the virgin mixtures. These results do not support the hypothesis that aged binder from the RAP makes the mix stiffer and harder to compact. The interaction of RAP and 52 Table 28. ANOVA for Compaction Experiment B. Table 29. ANOVA for compaction %Gmm including RAP. Factor Type Levels Values Analysis of Variance for %Gmm, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Aggregate fixed 2 Granite,Gravel Grad. Fixed 2 Coarse,Fine Binder fixed 4 B,E,G,M Temperature fixed 4 230,266,302,338 Agg. 1 15.8006 15.8006 15.8006 238.50 0.0000 Grad. 1 40.6406 40.6406 40.6406 613.44 0.0000 Binder 3 16.7987 16.7987 5.5996 84.59 0.0000 Temp. 3 5.4162 5.4162 1.8054 27.27 0.0000 Agg.*Grad. 1 11.5600 11.5600 11.5600 174.49 0.0000 Agg.*Binder 2 1.5781 1.5780 0.7890 11.92 0.0001 Agg.*Temp. 2 0.3931 0.3931 0.1966 2.97 0.0658 Grad.*Binder 2 0.8406 0.8406 0.4203 6.35 0.0048 Grad.*Temp 2 0.2356 0.2356 0.1178 1.78 0.1852 Temp.*Binder 8 2.2199 2.2199 0.2775 4.19 0.0016 AB1B2=GT1T2 1 0.0400 0.0400 0.0400 0.60 0.4428 AT1T2=B1B2G 1 0.3600 0.3600 0.3600 5.44 0.0262 AB1T1=B2GT2 1 0.0303 0.0306 0.0306 0.46 0.5016 AB1T2=B2GT1 1 0.8100 0.8100 0.8100 12.23 0.0014 AB2T1=B1GT2 1 0.0400 0.0400 0.0400 0.60 0.4428 AB2T2+B1GT1 1 0.0156 0.0156 0.0156 0.24 0.6308 Error 32 2.1200 2.1200 0.0662 Total 63 98.9000 Factor Type Levels Values Analysis of Variance for %Gmm, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 2 B,M Temp fixed 4 110,130,150,170 RAP fixed 2 0,15 Binder 1 2.20500 2.20500 2.20500 47.68 0.000 Temp 3 5.44500 5.44500 1.81500 39.24 0.000 RAP 1 3.00125 3.00125 3.00125 64.89 0.000 Binder*Temp 3 0.65500 0.65500 0.21833 4.72 0.015 Binder*RAP 1 0.66125 0.66125 0.66125 14.30 0.002 Temp*RAP 3 1.21375 1.21375 0.40458 8.75 0.001 Binder*Temp*RAP 3 0.29375 0.29375 0.09792 2.12 0.138 Error 16 0.74000 0.74000 0.04625 Total 31 14.21500

temperature also shows that the effect of the RAP was greater at higher compaction temperatures. Indirect Tensile Creep Compliance and Strength Gyratory specimens compacted at the four compaction temperatures were tested to determine indirect tensile creep compliance in accordance with AASHTO T 322. Creep com- pliance is the inverse of stiffness. Therefore, at very low tem- peratures, a mixture with lower compliance is able to strain more and avoid thermal fracture. The goal of this testing and analysis was to determine whether the low temperature mix properties were affected by the compaction tempera- ture. If an effect was detected, then the results would be analyzed to assess the potential that the change was due to binder degradation. Creep compliance results are summarized in Table 30. Since compliance values are greatly affected by test temper- ature, separate analyses were performed at each temperature. Figure 34 through Figure 36 show the change in compliance values for the modified binders at test temperatures −20°C, −10°C, and 0°C, respectively. Similarly, Figure 37 through 53 Figure 33. Interaction plot of RAP, binder, and temperature on %Gmm. Table 30. Summary of creep compliance results (Dt90 1 x 10-6 1/kPa) for different compaction temperatures. Temp Binder RAP MB 150 94.1 93.3 92.5 94.1 93.3 92.5 Temp 150 170 110 130 Binder B M Interaction Plot (fitted means) for %Gmm Test Temp. °C -20 -10 0 Comp. Temp. °C 110 130 150 170 110 130 150 170 110 130 150 170 Comp. Temp. °F 230 266 302 338 230 266 302 338 230 266 302 338 M 85.5 -19.5 0.0770 0.0716 0.0717 0.0661 0.1244 0.1111 0.1340 0.1088 0.3090 0.3001 0.2177 0.1997 N 84.3 -25.5 0.1416 0.1284 0.1077 0.1088 0.3447 0.2106 0.2106 0.1895 0.9503 0.7135 0.4367 0.4355 G 82.5 -24.2 0.1049 0.0834 0.0704 0.0688 0.1595 0.1302 0.1332 0.1006 0.4937 0.3711 0.3191 0.2160 H 78.3 -26.1 0.0851 0.0929 0.0792 0.0706 0.1702 0.1450 0.1678 0.1401 0.5753 0.5835 0.4825 0.2819 C 75.1 -38.7 0.1383 0.1394 0.1682 0.1509 0.3424 0.3527 0.4028 0.3221 1.3254 1.1280 1.1655 0.8607 I 71.8 -29.2 0.2295 0.1712 0.1792 0.1324 0.3237 0.3525 0.3516 0.1324 0.8144 1.0476 0.7209 0.4414 B 69.3 -37.3 0.1847 0.1808 0.1937 0.1926 0.4525 0.2987 0.4698 0.3873 1.6037 1.2855 1.4417 1.0198 F 67.8 -21.3 0.0728 0.0725 0.0527 0.0723 0.1978 0.1881 0.1598 0.1221 0.4417 0.3788 0.3420 0.2619 O 65.6 -29.7 0.1136 0.0737 0.0934 0.0869 0.2123 0.2077 0.1615 0.1493 0.8818 0.5780 0.4572 0.4249 K 65.3 -13.0 0.0580 0.0445 0.0439 0.0407 0.0668 0.0588 0.0551 0.0478 0.1755 0.1288 0.2243 0.1473 J 64.3 -20.7 0.0584 0.0529 0.0509 0.0581 0.0955 0.0795 0.0693 0.0738 0.2154 0.1886 0.1546 0.1691 E 60.9 -33.1 0.1678 0.1341 0.1237 0.1257 0.4213 0.1034 0.4169 0.3110 1.4816 1.2073 1.2343 0.6301 D 60.3 -31.7 0.1130 0.1001 0.0970 0.1034 0.2527 0.2488 0.2022 0.2209 1.1238 0.7832 0.6618 0.6020

54 0 0.05 0.1 0.15 0.2 0.25 100 110 120 130 140 150 160 170 180 Compaction Temperature C Dt (90 sec) x 10-6 1/kPa B C G H M N Figure 34. Creep compliance results for modified binders tested at 20°C. Figure 35. Creep compliance results for modified binders tested at 10°C. 0 0.1 0.2 0.3 0.4 0.5 100 110 120 130 140 150 160 170 180 Compaction Temperature C Dt (90 sec) x 10-6 1/kPa B C G H M N Figure 39 show the change in compliance for the set of un- modified binders. The compliance results generally follow the expected trends: • Lower test temperatures yield lower creep compliance results (higher stiffness), which means that the mixes lose their ability to relax thermal strains as the tempera- ture decreases. • Higher compliance values are generally observed for mixes having binders with lower low-temperature grades. For example, Mix B, which has a low PG true grade of −37.3°C, is more compliant than Mix M, which has a low PG true grade of −19.5. This observation confirms that a binder’s low PG number controls thermal cracking performance. From Figure 34 [the lowest test temperature (−20°C)], the modified binders are so stiff that compaction temperature appears to have a negligible effect. However, for the unmodi- fied binders, shown in Figure 37, most have a slight trend indi- cating that lower compaction temperatures resulted in slightly higher creep compliance values. From Figure 36 and Figure 39, which are plots of the creep compliance results at 0°C for the modified and unmodified

55 0 0.25 0.5 0.75 1 1.25 1.5 1.75 100 110 120 130 140 150 160 170 180 Compaction Temperature C Dt( 90 sec) x 10-6 1/Kpa B C G H M N 0 0.05 0.1 0.15 0.2 0.25 100 110 120 130 140 150 160 170 180 Compaction Temperature C Dt (90 sec) x10-6 1/kPa D E F I J K O Figure 37. Creep compliance results for unmodified binders tested at 20°C. binders respectively, it can be seen that the compliance drops substantially for some binders, including Binders B, C, and N of the modified binder set, and Binders E, D, O, and I for the unmodified binders. These binders are the ones with the low- est low temperature grades. This indicates that the binders with the lowest low temperature PG grades are more susceptible to a loss of compliance due to overheating. An ANOVA of creep compliance at −20°C with all binders confirmed that compaction temperature and binder ID are sta- tistically significant factors on compliance results. This analy- sis is shown in Table 31. As the data in Table 32 and Table 33 show, the same is true at the other creep compliance tempera- tures. However, the magnitude of the F-statistic for com- paction temperature relative to the F-statistic for Binder ID is much greater for the test results at 0°C, which indicates that the creep compliance test at this temperature is more sensitive to the compaction temperature. Therefore, compaction temper- ature does have a significant effect on low temperature prop- Figure 36. Creep compliance results for modified binders tested at 0°C.

56 0 0.1 0.2 0.3 0.4 0.5 100 110 120 130 140 150 160 170 180 Compaction Temperature C Dt (90 sec) x10-6 1/kPa D E F I J K O Figure 39. Creep compliance results for unmodified binders tested at 0°C. 0 0.25 0.5 0.75 1 1.25 1.5 1.75 100 110 120 130 140 150 160 170 180 Compaction Temperature C Dt (90 sec) x10-6 1/kPa D E F I J K O erties of the mixtures. Increasing the mixing and compaction temperatures can reduce the ability of a mixture to dissipate thermal stresses. Figure 40 illustrates a relationship between the creep compliance results at 0°C and binder low PG grade and com- paction temperature. This graph shows the strong relation- ship between the low PG grade and creep compliance, but also shows the influence of compaction temperature on this relationship. The main point of this figure is that mixing and compaction temperatures influence the potential for low tem- perature cracking, but the magnitude of the effect depends on the original low critical temperature of the binder and how hot the mix was heated. Following the indirect tensile creep tests, the specimens were tested to determine tensile strengths. Tensile strength tests were initially conducted at −20°C. However, a few spec- imens reached the maximum load cell capacity of the IDT system, so the remaining tests were conducted at −10°C. The tensile strength results are summarized in Table 34. An ANOVA on this data, shown in Table 35, indicates that the binder ID, compaction temperature, and their inter- action have significant effects on the tensile strengths. The Figure 38. Creep compliance results for unmodified binders tested at 10°C.

Factor Type Levels Values Analysis of Variance for Creep -20, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 13 B,C,D,E,F,G,H,I,J,K,M,N,O CompT fixed 4 110,130,150,170 Binder 12 0.1006398 0.1006398 0.0083866 42.98 0.000 CompT 3 0.0031606 0.0031606 0.0010535 5.40 0.004 Error 36 0.0070239 0.0070239 0.0001951 Total 51 0.1108243 Factor Type Levels Values Analysis of Variance for Creep -10, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 13 B,C,D,E,F,G,H,I,J,K,M,N,O CompT fixed 4 110,130,150,170 Binder 12 0.570865 0.570865 0.047572 18.66 0.000 CompT 3 0.028798 0.028798 0.009599 3.77 0.019 Error 36 0.091769 0.091769 0.002549 Total 51 0.691432 Factor Type Levels Values Analysis of Variance for Creep 0, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 13 B,C,D,E,F,G,H,I,J,K,M,N,O CompT fixed 4 110,130,150,170 Binder 12 7.08764 7.08764 0.59064 35.14 0.000 CompT 3 0.88120 0.88120 0.29373 17.48 0.000 Error 36 0.60509 0.60509 0.01681 Total 51 8.57393 Figure 40. Graph of relationships between low PG grade, compaction temperature, and IDT creep compliance at 0°C. Table 31. ANOVA for creep compliance at 20°C. Table 32. ANOVA for creep compliance at 10°C. Table 33. ANOVA for creep compliance at 0°C. y = 0.0615e-0.0882x R2 = 0.8207 y = 0.0517e-0.0881x R2 = 0.8108 y = 0.0493e-0.0855x R2 = 0.8206 y = 0.0456e-0.078x R2 = 0.871 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 -50 -45 -40 -35 -30 -25 -20 -15 -10 PG Low True Grade Cr ee p Co m pl ia n ce x 10 - 6 1/ kP a 110 130 150 170

interaction plot (Figure 41) shows that there were no consis- tent trends. Compaction temperature seems to have different effects on tensile strengths for the different binders. For exam- ple, a few binders show a peak in tensile strength at 130°C or 150°C, others show lower tensile strengths in the middle of the temperature range, and others show tensile strengths increasing throughout the compaction temperature range. The data were further analyzed for each binder separately to evaluate the significance of compaction temperature. In these separate analyses, only Binders K and O were found to have compaction temperature as a significant effect on tensile strength. For Binder K, a Tukey’s multiple comparison (α = 0.05) of tensile strengths at the four temperatures showed that the tensile strength at 110°C was significantly lower than for the other temperatures. However, this data set had a very limited number of samples. For Binder O, the tensile strengths at 110°C were significantly lower than the other temperatures, and the tensile strength at 130°C was significantly lower than 150°C, but not significantly different than 170°C. Overall, the tensile strength results varied from binder to binder such that 58 Table 34. Summary of indirect tensile strengths (MPa). Table 35. ANOVA for indirect tensile strength at 10°C. Test Temp. °C -20 -10 Comp. Temp. °C 110 130 150 170 110 130 150 170 Comp. Temp. °F 230 266 302 388 230 266 302 388 M 85.5 -19.5 Avg. 3.57 3.44 3.81 3.46St. Dev. 0.10 0.23 0.22 0.54 N 84.3 -25.5 Avg. 2.67 3.20 3.04 3.12St. Dev. 0.25 0.29 0.10 0.19 G 82.5 -24.2 Avg. 2.95 3.56 4.05 3.51St. Dev. 0.55 0.51 0.10 0.52 H 78.3 -26.1 Avg. 3.89 3.62 3.74 3.09St. Dev. 0.15 0.34 0.39 0.82 C 75.1 -38.7 Avg. 2.82 2.78 2.96 3.08St. Dev. 0.09 0.39 0.11 0.16 I 71.8 -29.2 Avg. 2.71 2.63 2.64 2.84St. Dev. 0.27 0.23 0.21 0.20 B 69.3 -37.3 Avg. 2.99 4.08 3.81 3.39St. Dev. 0.72 0.11 0.18 0.74 F 67.8 -21.3 Avg. 3.26 3.54 3.68 3.82St. Dev. 0.21 0.43 0.35 0.17 O 65.6 -29.7 Avg. 2.83 3.14 3.97 3.73St. Dev. 0.20 0.39 0.17 0.60 K 65.3 -13.0 Avg. 3.14 3.83 3.74 3.79St. Dev. * 0.07 0.23 ** J 64.3 -20.7 Avg. 3.52 3.31 3.74 3.76St. Dev. 0.35 0.28 0.27 0.07 E 60.9 -33.1 Avg. 2.78 2.75 2.75 2.95St. Dev. 0.15 0.28 0.29 0.28 D 60.3 -31.7 Avg. 3.43 3.48 3.64 3.49St. Dev. 0.57 0.43 0.29 0.25 * only one tensile strength result, ** only two tensile strength results Factor Type Levels Values Analysis of Variance for TS, using Adjusted SS for Tests Source DF Seq SS Adj SS Adj MS F P Binder fixed 11 C,D,E,F,H,I,J,K,M,N,O Temp fixed 4 110,130,150,170 Binder 10 17.87942 16.67716 1.66772 17.74 0.000 Temp 3 1.77062 1.84765 0.61588 6.55 0.000 Mix*Temp 30 6.20140 6.20140 0.20671 2.20 0.002 Error 100 9.40024 9.40024 0.09400 Total 143 35.25169 S = 0.306598 R-Sq = 73.33% R-Sq (adj) = 61.87%

it was not possible to make general conclusions or observations about trends regarding the effect of compaction temperature. Correlation of Mixing and Compaction Temperatures A key part of this research was to compare the predicted mixing and compaction temperatures from the candidate binder tests with the results of the mixture experiments. This section presents that analysis using correlations performed with MINITAB release 15 statistical software. The regressions are based on average values from replicate mix tests and binder tests. Outputs included graphical plots of the data, least- squares linear regression equations, 95% confidence intervals for the regressions, the residual error regression S, the coeffi- cient of determination R2, and the adjusted R2. An ANOVA table was also generated for each regression, which includes the observed significance level (P-value) for the regression equa- tions. For several correlations, one or two data points were identified as suspected outliers. Discussion of the outliers is presented as part of the analysis associated with the particular correlation. In each case where outlier data is suspected, the correlations are provided both with and without the question- able data. Figure 42 shows the correlations of the mixing tempera- tures from the Steady Shear Flow (SSF) method with the mix- ing temperatures to achieve 98% coating using the bucket mixer. The bucket mixer coating test results for Binder H was not considered reasonable as the predicted temperature to achieve the baseline coating percentage was outside of the experimental range. The regression statistics indicate the SSF mixing temperature explains only about 40% of the variation observed in temperatures needed to achieve the baseline coat- ing percentage with the bucket mixer. Binders that had the largest residuals were O, C, B, and I. The temperatures to achieve good coating for Binders O and C were much higher than predicted by the SSF method and for B and I coating was achieved at temperatures much lower than predicted by the SSF method. Figure 43 shows a similar set of plots of SSF mixing temper- atures versus the mixing temperatures to achieve 89% coating with the pugmill mixer. The regression statistics are somewhat poorer compared with those with the bucket mixer. For this data set, Binder E was considered as a possible outlier since the predicted temperature to achieve the baseline percentage was 222°F (106°C), which seems quite low and is outside of the experimental range. Figure 44 shows the correlations of mixing temperatures from the Phase Angle method with the coating test results using the bucket mixer. As noted above, the bucket mixer coat- ing test results for Binder H were not considered valid, so these data were removed and the correlations were performed again. The statistics for the regressions in these two plots are poorer than for the SSF method. As with the SSF correlations, the binders that have large residuals include Binders O, C, I, and B. Binder M also has a large residual in the Phase Angle–bucket mixer coating test correlations. This is the binder that includes the Sasobit® wax. The large residual with this binder could indicate that the Phase Angle method is not a good predictor of mixing temperatures for binders with Sasobit®, perhaps because the Phase Angle measurements are made at below temperatures where the Sasobit® wax melts. The poor correla- tions with O, C, I, and B for both the SSF and the Phase Angle methods is evidence that the problematic data likely arise 59 170150130110 4.00 3.75 3.50 3.25 3.00 2.75 2.50 Compaction Temperature (C) Te ns ile S tre ng th (M Pa ) N O C D E F H I J K M Binder Modified binders are shown with dashed connect lines Figure 41. Interaction plot for compaction temperature and binder on tensile strengths at 10°C.

from the bucket mixer coating results rather than the can- didate methods for determining mixing and compaction temperatures. Figure 45 shows the correlations of the Phase Angle method predicted mixing temperatures with the temperatures to achieve the baseline coating percentage in the pugmill mixer. As discussed with the SSF method–pugmill mixer correlation, the coating test results for Binder E in the pugmill were not considered valid. The regression statistics between the Phase Angle method and the pugmill mixer coating results are slightly better than for the SSF method. A summary of correlation statistics is shown in Table 36. Overall, the correlations between the mixing temperatures from the candidate methods and the coating test results are fairly weak, generally with R2 values in the range of 30 to 40%. However, the lack of strength of the correlations is likely due more to the coating test results that are based on curve-fitting through data from subjective measurements that lack good repeatability. Figure 46 and Figure 47 show correlations between the can- didate methods mixing temperatures and the midpoints of the mixing temperature range recommended by the binder suppli- ers. The correlation between the SSF method mixing tempera- ture and the suppliers’ recommended mixing temperatures is 60 340330320310300290280 425 400 375 350 325 300 275 250 SSF Mix T B uc ke t M ix T S 29.9023 R-Sq 43.5% R-Sq(adj) 38.4% Regression 95% CI O N MK J I H G F ED C B Bucket Mix T = - 70.9 + 1.259 SSF Mix T (a) 340330320310300290280 375 350 325 300 275 250 SSF Mix T B uc ke t M ix T S 22.1202 R-Sq 40.8% R-Sq(adj) 34.9% Regression 95% CI O N M K J I G F E D C B Bucket Mix T = 36.9 + 0.8928 SSF Mix T (b) Figure 42. Correlations of the SSF mixing temperature with the bucket mixer temperature for 98% coating: (a) all data; (b) excludes Binder H.

quite reasonable, with an R2 of 70%. The correlation of the Phase Angle method mixing temperatures with the suppliers’ recommended mixing temperatures is very weak unless the results from Binder M are removed. The issue with the Saso- bit® wax in Binder M was noted previously. With this data point removed, the correlation statistics improve consider- ably, although not as strong as with SSF method. However, it is also important to note that the regression equation between the phase angle method and producers’ recommendations was slightly closer to the line of equality than for the SSF method. Overall, these correlations show that both methods provide results generally consistent with field experience and therefore pass a test of reasonableness. Figure 48 and Figure 49 show the correlations between the workability tests and the results of the candidate methods for determining mixing and compaction temperatures. For these correlations, the temperatures midway between the mixing and compaction temperatures from the candidate methods were used as the independent variable. Although the correla- tions are weak as indicated by the low correlation coefficients, the regressions were statistically significant (α =0.05). No data were excluded from these correlations. However, most of the scatter is likely due to poor precision of the workability tests. Despite numerous attempts to improve the workability equip- ment and test method during this study, there is considerable doubt about the validity of the test as an indicator of binder 61 Figure 43. Correlations of the SSF mixing temperature with the pugmill mixer temperature for 89% coating: (a) all data; (b) excludes Binder E. 340330320310300290280 400 350 300 250 200 SSF Mix T Pu gm ill M ix T S 34.8156 R-Sq 35.7% R-Sq(adj) 29.9% Regression 95% CI O N M K J I H G F E D C B Pugmill Mix T = - 71.5 + 1.244 SSF Mix T (a) 340330320310300290280 375 350 325 300 275 250 SSF Mix T Pu gm ill M ix T _1 S 27.3356 R-Sq 34.6% R-Sq(adj) 28.1% Regression 95% CI O N M K J I H G F D C B Pugmill Mix T_1 = 28.4 + 0.9426 SSF Mix T (b)

stiffness on mix workability. The average temperature differ- ence for the duplicate runs on all of the workability tests was 26°F, which is a similar magnitude as the residuals for the cor- relations. Correlations between the compaction temperatures pre- dicted by the candidate methods with the results of the com- paction tests are shown in Figure 50 and Figure 51. Excluding the data for Binders I and J, both of the candidate methods’ compaction temperatures correlate well with the results from the mix compaction tests. Three binders had compaction test results that were outside of the experimental range for the tests: Binders I, J, and N. It is clear from the correlation graphs that the SGC compaction test temperatures for I and J are well above the reasonable range for these binders. Binder N is a heavily modified binder that was expected to require a rela- tively high temperature to achieve the baseline density level. Its compaction experiment results were just above the highest test temperature used in the compaction experiment. A summary of the regression statistics for the correlations between the candidate methods and mix test results is shown in Table 36. Also shown are the key statistics from the corre- lations with the respective midpoints of the binder producers’ 62 340330320310300 425 400 375 350 325 300 275 250 Phase Angle Mix T B uc ke t M ix T S 34.8178 R-Sq 23.5% R-Sq(adj) 16.5% Regression 95% CI O N MK J I H G F ED C B Bucket Mix T = - 48.5 + 1.153 Phase Angle Mix T (a) 340330320310300 360 340 320 300 280 260 Phase Angle Mix T B uc ke t M ix T _1 S 25.3382 R-Sq 22.4% R-Sq(adj) 14.6% Regression 95% CI O N M K J I G F E D C B Bucket Mix T_1 = 58.5 + 0.7970 Phase Angle Mix T (b) Figure 44. Correlation of Phase Angle Method mixing temperature with the bucket mixer temperature for 98% coating: (a) all data; (b) excludes Binder H.

63 340330320310300 400 350 300 250 200 Phase Angle Mix T Pu gm ill M ix T S 34.5577 R-Sq 36.7% R-Sq(adj) 30.9% Regression 95% CI O N M K J I H G F E D C B Pugmill Mix T = - 188.0 + 1.572 Phase Angle Mix T (a) 340330320310300 375 350 325 300 275 250 Phase Angle Mix T Pu gm ill M ix T _1 S 25.7628 R-Sq 41.9% R-Sq(adj) 36.1% Regression 95% CI O N M K J I H G F D C B Pugmill Mix T_1 = - 86.2 + 1.275 Phase Angle Mix T (b) Figure 45. Correlation of Phase Angle method mixing temperature with the pugmill mixer temperature for 98% coating: (a) all data; (b) excludes Binder E. Steady Shear Flow Phase Angle Mix Test Residual Error R 2 P-value Residual Error R 2 P-value Bucket 22.1 40.8 0.025 25.3 22.4 0.121 Pugmill 27.3 34.6 0.044 25.7 41.9 0.023 Workability 34.0 30.6 0.050 30.5 44.3 0.013 Compaction 18.7 68.4 0.002 16.7 74.8 0.001 Producers’ Midpoint 7.8 70.1 0.000 8.8 58.2 0.004 Table 36. Summary of correlation statistics.

340330320310300290280 340 330 320 310 300 290 280 SSF Mix T Pr od . M id po in t S 7.79965 R-Sq 70.1% R-Sq(adj) 67.4% Regression 95% CI O N MK J I H G F ED C B Prod. Midpoint = 136.0 + 0.5724 SSF Mix T Figure 46. Correlation of the SSF mixing temperature with the midpoint of the binder producers’ recommended mixing range. Figure 47. Correlation of the Phase Angle Method mixing temperature with the midpoint of the binder producers’ recommended mixing range: (a) all data; (b) excludes Binder M. 340330320310300 340 330 320 310 300 290 Phase Angle Mix T Pr od . M id po in t S 12.1468 R-Sq 27.4% R-Sq(adj) 20.8% Regression 95% CI O N MK J I H G F ED CB Prod. Midpoint = 170.9 + 0.4468 Phase Angle Mix T (a) 340330320310300 340 330 320 310 300 290 Phase Angle Mix T_1 Pr od . M id po in t S 8.81614 R-Sq 58.2% R-Sq(adj) 54.0% Regression 95% CI O N K J I H G F ED CB Prod. Midpoint = 115.7 + 0.6269 Phase Angle Mix T_1 (b)

65 Figure 48. Correlation of SSF mixing and compaction temperature midpoint with workability experiment equivalent torque temperature. Figure 49. Correlation of Phase Angle method mixing and compaction temperature midpoint with workability experiment equivalent torque temperature. 330320310300290280270 375 350 325 300 275 250 SSF mid EW T S 34.0257 R-Sq 30.6% R-Sq(adj) 24.3% Regression 95% CI O N M K J I H G FE D C B EWT = - 27.3 + 1.128 SSF mid 330320310300290 375 350 325 300 275 250 Phase Angle Mid EW T S 30.4978 R-Sq 44.3% R-Sq(adj) 39.2% Regression 95% CI O N M KJ I H G F E D C B EWT = - 241.3 + 1.785 Phase Angle Mid recommended mixing temperatures. These statistics are based on the correlations without suspected outliers, even where the statistics did not improve with these data excluded. Lower P-values indicate the correlation is more significant. A P-value of 0.05 or less is generally considered a statistically significant correlation. In general, the correlation statistics are similar for the two methods. The SSF method had better correlation sta- tistics with the bucket mixer coating test results and the pro- ducers’ recommended mixing temperatures. The Phase Angle method statistics appeared to be slightly better than the other correlations with mix test results. Statistical analyses were conducted to determine whether the SSF method or the Phase Angle method provided a better overall fit to the experimental data from the mixture tests and the binder producers’ recommended mixing temperatures. The analyses used an F-statistic to test the null hypothesis that the residual variances were equal, H0: σ2(SSF) = σ2(PA), for each regression summarized in Table 36. The F-test is an

approximation because it violates the independence assump- tion and, therefore, does not possess as much statistical power as the case when the chi-squared random variables are inde- pendent. The full analyses are provided in Appendix D. The analyses indicated that for each of the mix tests, there was not sufficient statistical evidence that either method explained more variability in the experimental data than the other, even when the R2 values differed by as much as 18.4%, as was the case for the correlations with coating tests results for the bucket mixer. Therefore, it can be concluded that the neither the SSF method nor the Phase Angle method is statistically better in cor- relating to mixing and compaction temperatures from mixture tests or producers’ recommendations. Comparison of SSF and Phase Angle Methods Although the candidate methods are based on different binder properties, there are some similarities between the SSF method and Phase Angle method. Both methods use a standard DSR and common parallel plate geometries for testing of the binder; therefore, they have some practical limitations includ- ing the test temperatures at which the properties are measured and at which particulate matter begins to have an effect. Correlations of the mixing and compaction temperatures determined by the two methods, shown in Figure 52 and Fig- ure 53 respectively, further illustrates the similarities. These 66 310300290280270260250 400 350 300 250 SSF Comp Co m p T S 43.7146 R-Sq 18.3% R-Sq(adj) 10.8% Regression 95% CI O N M K J I H G F ED C B Comp T = 5.3 + 1.071 SSF Comp (a) 310300290280270260250 350 325 300 275 250 SSF Comp Co m p T_ 1 S 18.7292 R-Sq 68.4% R-Sq(adj) 64.9% Regression 95% CI O N M K H G F ED C B Comp T_1 = - 96.62 + 1.375 SSF Comp (b) Figure 50. Correlation of the SSF Method compaction temperatures with the compaction experiment equivalent density temperatures: (a) all data; (b) excludes Binders I and J.

plots show that the results of the two methods are well cor- related, especially when Binder M is removed from the data set. The difference in the results for Binder M may be due to the warm mix asphalt additive, Sasobit®, included in this binder. Sasobit® is a Fischer-Tropsch wax that solidifies in asphalt between 149°F and 239°F (65°C to 115°C). The SSF test temperatures were slightly higher (up to 88°C) compared with test temperatures in the Phase Angle method, which went up to 80°C. It is possible that a phase change of the Sasobit® wax occurred in the temperature range between the two meth- ods, which affected the rheological behavior of the binder and resulted in significantly different mixing and compaction tem- peratures for Binder M. Based on the correlation equations, the mixing temperatures from the SSF and Phase Angle methods will be equivalent at 347°F (175°C). At the lower end of the mixing temperature range for typical paving-grade binders, the results of the SSF method will be about 13°F (7°C) lower than the mixing tem- perature from the Phase Angle method. Similarly, based on the correlation of compaction temperatures from the two 67 Figure 51. Correlation of the Phase Angle method compaction temperatures with the compaction experiment equivalent density temperatures: (a) all data; (b) excludes Binders I and J. 315310305300295290285280275 425 400 375 350 325 300 275 250 Phase Angle Comp Co m p T S 45.1004 R-Sq 13.0% R-Sq(adj) 5.1% Regression 95% CI O N M K J I H G F ED C B Comp T = - 65.9 + 1.269 Phase Angle Comp (a) 315310305300295290285280275 350 325 300 275 250 Phase Angle Comp Co m p T_ 1 S 16.7084 R-Sq 74.8% R-Sq(adj) 72.0% Regression 95% CI O N M K H G F ED C B Comp T_1 = - 320.3 + 2.072 Phase Angle Comp (b)

methods, the methods will give equivalent results at 318°F (159°C), which should be the upper end of the range of com- paction temperatures. At the lower end of the compaction tem- perature range for typical paving-grade binders, the results of the SSF method will be about 18°F (10°C) lower than the com- paction temperature from the Phase Angle method. Validation Experiment Results and Analysis A set of four independent binders were selected at the beginning of the study for a small validation experiment to verify the recommended method. This set of binders included a variety of crude sources, PG grades, and modification types, as shown in Table 37. Since the SSF method and the Phase Angle method had similar correlations with the mix tests and both appear to be viable options for determining mixing and compaction temperatures, both methods were carried for- ward in the validation experiment. A summary of the mixing and compaction temperatures determined from the SSF and Phase Angle methods for the validation binders is shown in Table 37. The true grades of each of the validation binders determined by NCAT differed from the grades reported by the producers. Also included in the table are the midpoints of the mixing and compaction temperatures recommended by the respective binder suppli- ers. Another point of reference is the equiviscous mixing and 68 340330320310300 350 340 330 320 310 300 290 280 270 Phase Angle Mix T SS F M ix T S 12.2325 R-Sq 65.6% R-Sq(adj) 62.5% Regression 95% CI O N M K J I H G F E D C B SSF Mix T = - 12.57 + 1.010 Phase Angle Mix T (a) 340330320310300 350 340 330 320 310 300 290 280 270 Phase Angle Mix T_1 SS F M ix T S 6.40025 R-Sq 91.0% R-Sq(adj) 90.1% Regression 95% CI O N K J I H G F E D C B SSF Mix T = - 79.22 + 1.228 Phase Angle Mix T_1 (b) Figure 52. Correlation of mixing temperatures from the SSF Method and the Phase Angle method: (a) all binders, (b) excludes Binder M.

compaction temperatures for the unmodified Binder Y, which were 333°F and 308°F, respectively. Overall, the temperatures from the Phase Angle method are lower than for the SSF method, but the differences are not con- sistent for this set of binders. For Binder Z, the results for the methods were very similar, but for Binder W, the difference between the results of the two methods was 20°F for the mix- ing temperature. Compared with the producers’ recommended mixing and compaction temperatures, the Phase Angle method under predicted the mixing and compaction temperatures for three of the four validation binders. The Phase Angle method also under predicted the mixing and compaction temperatures relative to the equiviscous method for the unmodified binder. The SSF method over predicted mixing temperatures for three of the four binders and over predicted compaction tempera- tures in just two cases. Both candidate methods over predict mixing and compaction temperatures for Binder X and under predict mixing and compaction temperatures for Binder Z. 69 Figure 53. Correlation of Compaction Temperatures from the SSF Method and the Phase Angle Method: (a) all binders and (b) excludes Binder M. 315310305300295290285280275 320 310 300 290 280 270 260 250 Phase Angle Comp SS F Co m p S 10.1739 R-Sq 72.2% R-Sq(adj) 69.6% Regression 95% CI O N M K J I H G F E D C B SSF Comp = - 68.99 + 1.194 Phase Angle Comp (a) 315310305300295290285280275 320 310 300 290 280 270 260 250 Phase Angle Comp_1 SS F Co m p S 5.60787 R-Sq 92.2% R-Sq(adj) 91.4% Regression 95% CI O N K J I H G F E D C B SSF Comp = - 131.8 + 1.414 Phase Angle Comp_1 (b)

The suppliers’ recommendations for binders are typically based on field experience using aggregate types, gradations, or other variables that may be substantially different than the materials and conditions used in this experiment. Mixture tests with the validation binders were conducted in the same manner and with the same materials as for the main mixture experiments. Mixture tests with the validation binders included coating tests with both mixer types, worka- bility tests, and compaction tests. Data from the mix coating tests using the bucket and pug- mill mixers for each of the validation binders are shown in Table 38. Following the same approach used for the main coating test experiment, these data were used to predict the mixing temperatures needed to achieve the baseline coating percentages for both mixer types. The results of the coating test experiments with the validation binders are shown in Table 39. It can be seen that the results of the coating tests with the pugmill mixer are reasonable for each of the binders, ranging from 291°F for the unmodified Binder Y to 341°F for the SBS modified Binder W. However, the temperatures for achieving the baseline coating percentage with the bucket mixer are excessive and are extrapolated outside of the temperature range of the experiment for the three modified binders. Table 40 summarizes the results of the workability tests for the validation binders. Only one sample was tested for each binder. As with the main workability experiment, the regres- sions from these workability tests were used to estimate the temperature at which the torque was equal to 10 Nm for each binder. These results appear to be reasonable and follow the expected trend that higher PG binders will require a higher temperature to achieve the same workability. Mix compaction tests with the validation binders followed the same protocol as with the main compaction experiment 70 Table 37. SSF and Phase Angle method results for validation binders. Table 38. Results of coating tests with validation binders. Table 39. Predicted mixing temperatures for good coating for the validation binders. Binder I.D. Binder True Grade SSF Method Phase Angle Method Midpoint of Producer’s Recommendation Mixing Temp. (ºF) Comp. Temp. (ºF) Mixing Temp. (ºF) Comp. Temp. (ºF) Mixing Temp. (ºF) Comp. Temp. (ºF) W 90.0 -17.8 358 329 338 311 345 325 X 74.2 -27.9 345 315 338 310 312 282 Y 73.0 -21.4 325 295 314 291 321 298 Z 81.9 -20.1 327 300 325 300 350 320 Percentage of Coated Aggregate Particles by ASTM D2489 Mixer Type Pugmill Bucket Mixing Temp. °C 120 140 160 180 120 140 160 180 Mixing Temp. °F 248 284 320 356 248 284 320 356 W 90.0 -17.8 17.7 62.2 76.4 86.1 43.9 66.5 81.7 88.6 X 74.2 -27.9 36.7 70.7 80.3 93.3 35.0 26.4 97.4 99.8 Y 73.0 -21.4 73.7 92.9 92.4 91.0 75.3 83.6 98.7 95.2 Z 81.9 -20.1 36.8 79.4 85.3 92.1 27.6 44.5 73.6 98.5 ID True Grade Pugmill Mixer Bucket Mixer a b T for 89% Coating A b T for 97% Coating W 90.0 -17.8 4508.4 0.0609 341 174.784 0.0413 406 X 74.2 -27.9 1614.4 0.0570 331 30484.3 0.0744 365 Y 73.0 -21.4 27.68 0.0373 291 57.00 0.04256 349 Z 81.9 -20.1 6693.6 0.0699 311 9506.3 0.0682 365

except that for the validation binders, compaction tests were only performed at the three temperatures: 130°C, 150°C, and 170°C. Table 41 shows the results of the compaction tests for the validation binders. It can be seen from these data that none of the mixes reached the baseline density of 92.9% of Gmm established in the main compaction experiment. This is probably due to a slight adjustment to the SGC internal angle during routine calibration of the machine that took place in the time lag between the main compaction experi- ment and the validation tests. Therefore, the temperature- density regression was used to estimate the temperature to 71 Table 40. Summary of workability test results for the validation binders. Table 41. Results of compaction tests with validation binders. ID Workability Regression Equation R2 ºC ºF W y = -0.0024x2 - 0.3432x + 20.098 0.94 155 311 X y = 0.0021x2 - 0.9269x + 108.17 0.79 150 302 Y y = 0.0059x2 - 1.8786x + 165.73 0.57 139 282 Z y = 0.0048x2 - 1.5287x + 136.05 0.86 153 308 Binder I.D. Binder True Grade %Gmm at 25 Gyrations Regression Equation (T is temperature, °C) Compaction Temperature for 92.0% Gmm,°F (°C) 266ºF (130ºC) 302ºF (150ºC) 338ºF (170ºC) W 90.0 -17.8 91.5 91.8 92.1 %Gmm = 0.0135T+89.756 344 (173) X 74.2 -27.9 91.7 91.5 92.8 %Gmm = 0.028T+87.926 294 (146) Y 73.0 -21.4 91.8 92.4 92.4 %Gmm = 0.014T+90.053 282 (139) Z 81.9 -20.1 91.8 92.3 92.3 %Gmm = 0.125T+90.213 301 (149) achieve a density level of 92.0% of Gmm. The compaction temperatures based on this approach seems reasonable for three of the four binders. The predicted compaction temper- ature for Binder W is outside of the experimental range and appears to be too high. Table 42 summarizes the differences between results of the mixture tests and the results from candidate methods for each of the validation binders. Since the coating test results with the bucket mixer were so far outside of the experimental range and outside of reasonable limits, they were not included in this analysis. Comparing the absolute differences for the two can- didate methods, it can be seen that results with the Phase Angle method agree more closely with the mix tests than the SSF method. However, it also can be seen that many of the dif- ferences are substantial for both of the candidate methods. Although these large differences may be considered to be an indication that neither of the candidate methods provides accurate mixing and compaction temperatures, it is even more likely that the results of the mix tests are less reliable than the candidate binder tests. Binder I.D. SSF Mixing Temp. – Temp. for 89% Coating in Pugmill Mixer Phase Angle Mixing Temp - Temp. for 89% Coating in Pugmill Mixer SSF Mix & Comp. Midpoint Temp. - Temp. for Equal Workability Phase Angle Mix & Comp. Midpoint Temp. - Temp. for Equal Workability SSF Compaction Temp. - Temp. for 92.0% Gmm Phase Angle Compaction Temp. - Temp. for 92.0% Gmm W +17 -3 +33 -15 -15 -33 X +14 +7 +28 +21 +21 +16 Y +34 +23 +28 +13 +13 +9 Z +16 +14 +6 -1 -1 -1 Σ|Δ| 81 47 95 50 50 59 Table 42. Summary of differences (°F) between mix test results and candidate methods results for the validation binders.

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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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