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From page 42... ...
42 RAP Drying Experiment Figure 3-1 shows the drying curves from the RAP drying experiment. These plots show that about 6 hours were necessary to dry the approximately 24 kg samples using a conventional drying oven temperature of 110°C (230°F)
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43 Figure 3-1. Moisture content changes for RAP dried in an oven and fan drying.
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From page 44... ...
44 backcalculated Gsb values were about 0.10 higher, which would significantly affect VMA results for high RAP content mixes. To illustrate the impact of these results, the three different RAP aggregate Gsb results were used in the calculation of the total aggregate blend Gsb and VMA values for the mix designs that are presented in detail later in the report.
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From page 45... ...
45 binder. The 0 and 55 percent RAP content designs were also completed with a PG 58-28 and a PG 70-28 from a second binder source, noted with a "B" following the PG grade.
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0% RAP 0% RAP 25% RAP 55% RAP Original 55% RAP Original Nominal Max.
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From page 47... ...
0% RAP 0% RAP 25% RAP 55% RAP WMA 55% RAP 55% RAP Percent Passing 2.36 mm 28.7 28.7 28.3 28.0 28.0 28.0 Percent Passing 1.18 mm 20.3 20.3 20.3 20.3 20.3 20.3 Percent Passing 0.60 mm 14.8 14.8 14.8 15.1 15.1 15.1 Percent Passing 0.30 mm 10.3 10.3 10.5 11.2 11.2 11.2 Percent Passing 0.15 mm 6.9 6.9 7.3 8.2 8.2 8.2 Percent Passing 0.075 mm 5.2 5.2 5.6 6.1 6.1 6.1 Optimum AC, % 5.5 6.0 5.7 6.5 6.5 6.1 AC from Virgin Binder, % 5.5 6.0 4.2 3.5 3.5 3.1 AC from RAP, % 0 0 1.54 3.0 3.0 3.0 RAP Binder/Total Binder, % 0 0 27 46 46 49 Va, % 3.9 4.1 3.7 4.1 3.7 3.7 VMA, % 14.0 15.2 14.1 15.3 15.1 15.0 Vbe, % 10.1 11.1 10.4 11.2 11.4 11.3 VFA, % 72.2 73.4 73.8 73.4 75.4 75.1 Effective AC, % 4.4 4.8 4.5 4.9 4.9 4.9 Dust/Asphalt Ratio 1.2 1.1 1.2 1.2 1.2 1.2 TSR 0.86 -- 0.75 0.67 0.71 -- Table 3-6. (Continued)
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From page 48... ...
48 Minnesota Mix Designs Four mixes were designed with the Minnesota materials. Two of the mixes were 9.5-mm NMAS mixes, and the other two were 19.0-mm NMAS mixes.
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From page 49... ...
49 0% RAP 40% RAP 0% RAP 40% RAP Nominal Max.
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From page 50... ...
50 PG Materials Source RAP (%) Difference between Soft Primary and Secondary Binders Difference between Stiff Primary and Secondary Binders Difference between Soft and Stiff Primary Binders Difference between Soft and Stiff Secondary Binders 58-34 UT 0 -0.5 -0.2 -0.4 -0.1 25 -- -0.4 -- -- 55 0.4 -0.1 0.3 -0.2 58-28 NH 0 0 0 0 0 25 -- 0 -- -- 55 -0.1 0 0 0.1 Table 3-10.
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From page 51... ...
51 sources were used. Since these differences in optimum asphalt contents included virgin mix designs, then a problem with compatibility of virgin and RAP binders can be ruled out as a possible cause.
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From page 52... ...
52 RAP binder percentage for three of the four 40 percent RAP mixes was lower than the aggregate content because little or no fine fractionated RAP was used. For both Minnesota mixes, all the predicted composite binder critical temperatures increased by 2 to 5 degrees for the 40 percent RAP mixes compared to the virgin mixes.
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From page 53... ...
53 Figure 3-7. New Hampshire mixtures using PG 70-28A master curves.
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From page 54... ...
54 using the PG 70-28 binder from Source B was actually the least stiff at the high-temperature range of the master curve. Overall, the results suggest that as RAP content increases, the effect of the virgin binder grade becomes less influential as would be expected due to the higher proportion of reclaimed binder.
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From page 55... ...
55 As with the effect of the virgin binder grade, which showed less effect on the mixture as RAP content increased, the source of the virgin binder also appeared to make less difference on the mixture stiffness for the 55 percent RAP mixtures than it did for the virgin mixtures. To statistically assess the effect of the mix factors on mixture stiffness, a general linear model (GLM)
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From page 56... ...
56 (low-temperature, high-frequency) and middle (intermediate temperatures)
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From page 57... ...
57 however, a 60 percent difference in mixture stiffness was seen through the intermediate range of temperatures. Effect of Binder Source on Mixture Stiffness Figures 3-22 and 3-23 show the master curves for the virgin and 55 percent RAP mixtures using different binder sources.
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From page 58... ...
58 intermediate temperatures, the average difference between the HMA and WMA mixtures is approximately 10 percent. A 15 percent difference in mixture stiffness was noticed at the hot end of the master curve while the difference at the cold end of the master curve is less than 6 percent.
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From page 59... ...
59 The materials from the two sources had different characteristics, and the mix designs differed by gradations, volumetric properties, and virgin binder grades. Also as expected, mix designs with 55 percent RAP were significantly stiffer than virgin mixes.
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60 all four temperatures are given in Table 3-17. The statistical analyses confirm the RAP content is again the most critical factor that affects the mixture stiffness for the Minnesota mixtures at three of the four temperatures.
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From page 61... ...
61 between the measured and predicted values. The "actual" measured critical temperatures shown are from the tank sample virgin binders, so there was no extraction or recovery testing to confound the results.
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From page 62... ...
62 Figure 3-29 compares the backcalculated and measured critical high temperatures for the 32 mixtures. Although the procedure typically over-predicts the critical high temperature for the laboratory mixtures (87.5 percent)
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63 Figure 3-29. Comparison of backcalculated and measured critical high temperatures.
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64 Figure 3-31. Backcalculated and measured phase angles at high temperatures.
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From page 65... ...
65 binders from the dynamic modulus data using the Hirsch and C-A models. The errors at the high critical temperature properties could be due to extrapolating the model to at least 15°C beyond measured data.
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From page 66... ...
66 criteria. The contractor who supplied these materials does not use anti-stripping additives.
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From page 67... ...
67 NMAS mixes, respectively. Therefore, as percentages of the total binder, the anti-strip dosages were 0.31 percent and 0.47 percent for the 9.5-mm mix, and 0.28 percent and 0.42 percent for the 19.0-mm mixes.
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From page 68... ...
68 Flow Number Results Plots of total accumulated permanent strain versus test cycles were constructed for each mix to visually evaluate the flow number test results. Figure 3-38 shows the average results for the 55 percent RAP mixes from New Hampshire as an example.
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From page 69... ...
69 New Hampshire Mix Designs Figure 3-40 shows the accumulated strain at 20,000 cycles for the New Hampshire mixes. As can be seen, the mixes containing 50 percent RAP had lower accumulated strain than their virgin mix counterparts for each grade of virgin binder.
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From page 70... ...
70 virgin mix, even though its asphalt content was 0.3 percent higher. Comparing the results of the mixes with the different binder grades shows that the virgin mix with the unmodified binder had less deformation than the corresponding mixes with the polymer binder.
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71 binder high performance grade (58, 64, and 70°C)
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From page 72... ...
72 the cracking resistance of the mix design. The mix design with the softer, unmodified virgin binder has a much higher fracture energy.
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From page 73... ...
73 Source DF Seq SS Adj SS Adj MS F P Material Source 1 0.8585 3.9621 3.9621 4.35 0.046 Virgin Binder Grade 3 4.2818 7.5661 2.5220 2.77 0.059 RAP % 2 31.0556 31.0556 15.5278 17.04 0.000 Material Source* RAP % 2 3.7222 3.7222 1.8611 2.04 0.147 Error 30 27.3378 27.3378 0.9113 Total 38 67.2559 Table 3-22.
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From page 74... ...
74 previous mix designs, the virgin mixes have higher fracture energies than the mixes containing RAP. It can also be seen that the 9.5-mm NMAS mixes have higher fracture energies than the 19.0-mm NMAS mixes.
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From page 75... ...
75 The mix designs from the three sources were tested for low-temperature properties. The Florida mix designs were not evaluated for thermal cracking properties since this is not a distress that occurs in that state.
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76 Binder Temp (°C)
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77 Figure 3-51. Fracture energy results for New Hampshire mixtures.
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78 Binder Temp (°C)
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79 SCB test results, most values of coefficient of variation were less than 25 percent, which is reasonable for creep testing of asphalt mixtures. Higher values of S(60s)
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80 σ −19 (MPa) Binder Type RAP (%)
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From page 81... ...
81 content mix with PG 58-28A was lower than the LTPP temperature for a 10°C/h temperature drop rate. For mixes with the PG 70-28 binder, thermal stresses were not affected by RAP content.
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From page 82... ...
82 Figure 3-56. SCB fracture toughness results for Utah mixtures.
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From page 83... ...
83 Response: KIC Parameter Coefficient Std. Error t p-value Significance Intercept 0.440 0.049 8.980 0.000 Significant Temp-15 0.360 0.070 5.143 0.000 Significant Temp-25 0.592 0.070 8.457 0.000 Significant RAP 25% 0.018 0.070 0.257 0.803 RAP 55% 0.311 0.070 4.443 0.000 Significant Temp*
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From page 84... ...
84 Figure 3-58. BBR stiffness results for Utah mixes.
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From page 85... ...
85 Similar to the previous section, S(60s)
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86 Binder Type RAP (%)
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From page 87... ...
87 • Low temperature with two different levels in BBR test: -14°C (control) and -24°C; • RAP content with two different levels: 0 (control)
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From page 88... ...
88 Table 3-39 shows the results of ANOVA on fracture energy and fracture toughness for the Minnesota mixtures. It was observed that KIC for the 19.0-mm 40 percent RAP mixture was significantly higher compared to the virgin 9.5-mm mixture.
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From page 89... ...
89 NMAS Temp (°C)
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From page 90... ...
90 in specimens as temperature decreases due to a reduced ability to creep. For NMAS 9.5 mm, lower values of m(60s)
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From page 91... ...
91 Figure 3-66. Thermal stresses at –15C for 1/hr and 10/hr cooling rates for Minnesota mixes.
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