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OCR for page 66
66 Comp T = 5.3 + 1.071 SSF Comp I Regression 95% CI 400 S 43.7146 R-Sq 18.3% R-Sq(adj) 10.8% J 350 N G Comp T H M 300 C F O B D E K 250 250 260 270 280 290 300 310 SSF Comp (a) Comp T_1 = - 96.62 + 1.375 SSF Comp Regression 350 N 95% CI S 18.7292 G H R-Sq 68.4% R-Sq(adj) 64.9% 325 M Comp T_1 300 C F O B 275 D E K 250 250 260 270 280 290 300 310 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. approximation because it violates the independence assump- Comparison of SSF and tion and, therefore, does not possess as much statistical power Phase Angle Methods as the case when the chi-squared random variables are inde- pendent. The full analyses are provided in Appendix D. Although the candidate methods are based on different The analyses indicated that for each of the mix tests, there was binder properties, there are some similarities between the SSF not sufficient statistical evidence that either method explained method and Phase Angle method. Both methods use a standard more variability in the experimental data than the other, even DSR and common parallel plate geometries for testing of the when the R2 values differed by as much as 18.4%, as was the case binder; therefore, they have some practical limitations includ- for the correlations with coating tests results for the bucket ing the test temperatures at which the properties are measured mixer. Therefore, it can be concluded that the neither the SSF and at which particulate matter begins to have an effect. method nor the Phase Angle method is statistically better in cor- Correlations of the mixing and compaction temperatures relating to mixing and compaction temperatures from mixture determined by the two methods, shown in Figure 52 and Fig- tests or producers' recommendations. ure 53 respectively, further illustrates the similarities. These

OCR for page 66
67 Comp T = - 65.9 + 1.269 Phase Angle Comp 425 I Regression 95% CI 400 S 45.1004 R-Sq 13.0% 375 R-Sq(adj) 5.1% J 350 N Comp T H G 325 M 300 C F O B 275 D E K 250 275 280 285 290 295 300 305 310 315 Phase Angle Comp (a) Comp T_1 = - 320.3 + 2.072 Phase Angle Comp 350 N Regression 95% CI G H S 16.7084 R-Sq 74.8% 325 M R-Sq(adj) 72.0% Comp T_1 300 C F O 275 B D E K 250 275 280 285 290 295 300 305 310 315 Phase Angle Comp (b) 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. plots show that the results of the two methods are well cor- ods, which affected the rheological behavior of the binder and related, especially when Binder M is removed from the data resulted in significantly different mixing and compaction tem- set. The difference in the results for Binder M may be due to peratures for Binder M. the warm mix asphalt additive, Sasobit, included in this Based on the correlation equations, the mixing temperatures binder. Sasobit is a Fischer-Tropsch wax that solidifies in from the SSF and Phase Angle methods will be equivalent at asphalt between 149F and 239F (65C to 115C). The SSF 347F (175C). At the lower end of the mixing temperature test temperatures were slightly higher (up to 88C) compared range for typical paving-grade binders, the results of the SSF with test temperatures in the Phase Angle method, which went method will be about 13F (7C) lower than the mixing tem- up to 80C. It is possible that a phase change of the Sasobit perature from the Phase Angle method. Similarly, based on wax occurred in the temperature range between the two meth- the correlation of compaction temperatures from the two