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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-
18
modified binders to illustrate the lower compliance results
16 for the modified binders. As with the unmodified binders, the
14 modified binders show a trend of decreasing Jnr as the SEP
12 temperature was increased. However, there is no evidence of
10
degradation of the binders due to the exposure to the elevated
Jnr (1/Pa) temperatures in the SEP test.
8
In summary, the assessment of changes in binder proper-
6
ties due to the conditioning of the samples to elevated tem-
4 peratures in the SEP test indicates that all binders increase in
2 stiffness with higher temperatures. The magnitudes of the
0 property changes differ among the binders in the experiment,
H
B 0 but with the limited data set there does not appear to be any
C 130 consistent trend that binders from particular crude sources
Binder ID M 150
N 170
are more temperature susceptible than others. Also, modified
G 190 SEP Temp. (C) and unmodified binders generally appear to be affected by
high temperatures to similar magnitudes. The results do not
Figure 24. MSCR Jnr results at 3200 Pa stress for
modified binders.
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
binders exhibit more recoverable strain (i.e., are more elastic) cause significant damage to the binders.
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 Mixture Testing
Slope/Canadian crude blend. This binder was consistently This section presents the results of the tests with the binders
among the binders with the greatest property changes due to in mixture tests over a range of mixing and compaction tem-
the SEP conditioning. It was also the binder with the highest peratures. Results are given for the coating tests, the workabil-
opacity and, therefore, it may have lost some volatile compo- ity tests, the compaction tests, and the indirect tensile creep
nents that caused a substantial increase in stiffness. compliance and strength tests.
Figure 24 shows the effect of SEP temperature on Jnr for
modified binders. As with the unmodified binders, the Jnr data Mixture Coating Tests
used to evaluate degradation were from the high grade temper-
ature, except for the PG 82 binders (M, N, and G). For these Results of the coating tests are summarized in Table 19.
three binders, the creep recovery tests were not performed at The table shows the percentage of coated particles determined
Table 19. Summary of coating test results.
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
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Table 20. ANOVA results for mix coating experiment.
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
by the Ross count method as mixing temperatures were of increased coating at higher temperatures, but that the
increased from 248°F to 356°F (120°C to 180°C). effect is not linear. The results also show that the bucket
Analysis of variance (ANOVA) is a common method of mixer provided better coating than the pugmill. This seems
analyzing data from a statistical experimental design to assess to conflict with the hypothesis that the bucket mixer would
differences associated with experimental treatments. Out- be less efficient than the pugmill due to its lower mixing
put from the ANOVA for the coating experiment is shown speed (slower shear rate). However, besides mixing speed,
in Table 20. From these results, it can be seen that all three the action of the two mixers is very different. The tumbling
of the main factors (binder ID, mixing temperature, and action of the bucket mixer, like that of a drum mix plant, allows
mixer type) were highly significant. The interactions of these aggregate particles to stay in contact with the binder and other
factors were also statistically significant, however, based on the coated particles. This could be a more efficient coating process
F values, not nearly to the same degree as the main factors by than a pugmill, which is a more violent churning action with
themselves. aggregate particles tossed into space, especially when the pug-
The main effects plots for the coating test experiment are mill is under filled.
shown in Figure 25. All of the modified binders, except For each binder, the coating percentages were related to
Binder B, plot below the overall mean for percent coating, mixing temperatures using Sigmoid functions of the form:
which indicates that aggregates are harder to coat with the
modified binders under the same conditions. The tempera- 1
C= (8)
ture effect on coating percentage follows the expected trend 1 + ae - b T
Main Effects Plot for %Coating
Fitted Means
Binder Temp
90
80
70
Mean
B C D E F G H I J K M N O 120 140 160 180
Mixer
90
Modified binders are shown
with triangle symbols
80
70
Bucket Pugmill
Figure 25. Effects of binder, temperature, and mixer on coating percentage.
