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57 SAFT RTFOT 10 10 8 8 Change in Td for RTFOT Aging, C Change in Td for SAFT Aging, C 6 6 4 4 2 2 0 0 -2 -2 -2 -1 0 1 2 3 4 5 6 7 8 9 10 Change in Td for R30 Aging, C Figure 3-46. Comparison of change in defining temperature for short-term mixture and binder aging. The Spearman's rank correlation coefficient for the SAFT test. Table 3-39 summarizes average aging indices for rankings is only 0.60 and the correlation is not significant at the neat and modified binders for 10 kPa unaged binder the 95 percent level. stiffness. Data are presented for four aging procedures (AASHTO R30 mixture aging and binder aging using the RTFOT, MGRF, and SAFT). In computing the averages 3.7 Short-Term Aging of Modified and standard deviations given in Table 3-38, the data Binders for the EVA binder were eliminated due to the testing dif- One of the purported issues with the RTFOT is that the ficulties caused by phase separation that were discussed aging of modified binders is less because the higher viscos- previously. ity modified binders do not maintain a thin film during the The average aging indices for neat and modified binders are compared in Figure 3-48 for the four short-term aging Table 3-36. Aging indices for AASHTO R30 procedures. The error bars shown in Figure 3-48 are 95 per- conditioning based on back-calculated binder cent confidence intervals for the average. These comparisons modulus values. show that there is little difference in the average aging index for the neat and modified binders included in NCHRP Pro- Aging Indices from AASHTO R30 for Various Unaged Binder Modulus Values ject 9-36. 1 10 100 1,000 10,000 100,000 Table 3-39 also summarizes the results of hypothesis test- Binder kPa kPa kPa kPa kPa kPa ing for the average of the mean 10-kPa aging index between AAC-1 4.78 3.50 2.34 1.43 0.84 0.55 AAD-2 6.46 4.53 3.01 1.91 1.19 0.77 neat and modified binders for the four short-term aging AAF-1 5.26 4.49 3.61 2.68 1.83 1.17 procedures. This testing shows that the average aging index AAM-1 2.95 2.62 2.23 1.80 1.40 1.00 is the same for neat and modified binders for short-term ABL-1 3.43 2.89 2.32 1.77 1.30 0.97 ABM-2 1.70 1.79 1.87 1.89 1.73 1.32 mixture aging in accordance with AASHTO R30 and short- Airblown 6.66 4.34 2.71 1.65 1.02 0.72 term binder aging in the RTFOT and the MGRF. For the ALF 3.33 2.74 2.24 1.82 1.48 1.19 SAFT, the hypothesis testing shows that the average aging Citgoflex 0.85 1.20 1.72 2.40 3.09 2.79 Elvaloy 6.13 4.34 2.94 1.93 1.26 0.86 index for the neat binder is greater than that for the modi- Novophalt 2.61 2.66 2.58 2.34 1.94 1.43 fied binder.

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58 SAFT RTFOT MGRF Equality 5.0 4.5 RTFOT, SAFT, or MGRF Aging Index 4.0 3.5 RTFOT R2 = 0.87 3.0 MGRF 2.5 R2 = 0.67 2.0 SAFT R2 = 0.26 1.5 1.0 0.5 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 R30 Aging Index Figure 3-47. Comparison of 10 kPa aging indices for mixture and binder testing. Table 3-37. Regression analysis of Table 3-38. Comparison of ranking of aging indices from AASHTO R30, binder aging indices. RTFOT, SAFT, and MGRF. Binder Rank Model Measure Value R30 RTFOT SAFT MGRF R2 0.87 AAC-1 5 7 1 1 Slope 0.41 AAD-2 1 2 3 3 AAF-1 2 1 2 2 RTFOT vs R30 p-value for slope 0.0002 AAM-1 9 6 7 10 Intercept 1.04 ABL-1 6 5 6 8 p-value for intercept >0.0001 ABM-2 10 10 5 9 R2 0.26 Airblown 3 3 4 6 Slope 0.25 ALF 7 9 8 7 SAFT vs R30 p-value for slope 0.0639 Citgoflex 11 11 11 11 Intercept 0.88 Elvaloy 4 4 10 4 p-value for intercept 0.0563 Novophalt 8 8 9 5 R2 0.67 Spearman Rank 0.91 0.60 0.80 Slope 0.30 Correlation Coefficient p-value 0.0001 0.0510 0.0031 MGRF vs R30 p-value for slope 0.0012 Intercept 1.42 p-value for intercept 0.0010 Table 3-39. Average 10 kPa aging indices for neat and modified binders. Hypothesis Test of Equality of Average Neat Modified Aging Index for Neat and Modified Binders Method Standard Standard Pooled Average Average t tcritical Conclusion Deviation Deviation s R30 3.30 1.08 3.05 1.32 1.19 0.43 2.26 No difference RTFOT 2.44 0.46 2.26 0.58 0.52 0.55 2.26 No difference MGRF 2.44 0.47 2.30 0.35 0.42 0.54 2.26 No difference SAFT 1.97 0.48 1.34 0.27 0.40 2.60 2.26 Neat > Modified

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59 Neat Modified 5.0 4.5 4.0 3.5 Aging Index 3.0 2.5 2.0 1.5 1.0 0.5 0.0 R30 RTFOT MGRF SAFT Aging Procedure Figure 3-48. Comparison of average 10-kPa aging indices for neat and modified binders.