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conditioning fluid. If the specimens are to be conditioned in Table 22. Significance of flow number ruggedness
a water bath, they should be sealed in plastic to keep the water test factors for unconfined tests with the ITC SPT
from penetrating the specimen. on the dense mixture.
4. Strain level. The current strain control of ±25 strain Permanent Strain at
Flow 500 1000 2000
is acceptable for unconfined tests. However, the strain con- Factors Number cycles cycles cycles
trol should be improved to ±15 strain to accommodate con- Equilibrium Temperature (-1 vs +1 C) 0.06 0.51 0.22 0.05
fined testing which may be necessary for some mixture types. Transfer time (3 vs 5 min) 0.26 0.87 0.93 0.66
Conditioning Fluid (Water vs Air) 0.64 0.06 0.02 0.02
5. Membrane. Unconfined tests should not be performed End Condition (Mill vs Saw) 0.29 0.02 0.02 0.04
with the membrane on the specimen. The membrane in- Friction Reducer (Teflon vs Latex) 0.02 0.94 0.42 0.03
creases the dynamic modulus and phase angle for moderate Axial Stress (135 vs 145 kPa) 0.14 0.80 0.43 0.12
to high temperature tests. It also significantly reduces the Contact Stress (5 vs 10 kPa) 0.63 0.30 0.27 0.35
quality of the deformation and phase angle data.
6. Confinement. The current confining pressure control are presented in Table 22 and Table 23 for the unconfined
of ±2 percent is acceptable in confined tests. Over this range tests on the dense graded mixture; Table 24 and Table 25 for
of control, the dynamic modulus and phase angle are ex- the confined tests on the dense graded mixture; and Table 26
pected to vary by 0.8 percent and 0.2 degrees, respectively. and Table 27 for the confined tests on the SMA mixture. Each
table presents p-values indicating the significance of the re-
7. End condition. There was no significant difference in
gression coefficients for each of the factors included in the
the measured material properties between milled specimen ends
ruggedness experiment. As discussed previously for the dy-
and sawed specimen ends. The effect of end condition on the
namic modulus, low p-values indicate the regression coeffi-
data quality was small and not consistent. The use of sawed spec-
cient is statistically significant and the ruggedness factor
imen ends is acceptable for dynamic modulus tests in the SPT.
affects the results of the test. A critical p-value of 0.10 was
8. Friction reducer. There was no significant difference used in this analysis. Factors with p-values equal to or less
in the measured material properties between greased latex than 0.1 are shown in bold in Table 22 through Table 27.
and TeflonTM as the end friction reducer. The effect of the fric- Table 28 and Table 29 were constructed to combine the re-
tion reducer on the data quality was small and not consistent. sults for the tests in both laboratories. These tables present the
The use of either greased latex of TeflonTM as the end friction percentage of times a specific factor was found to be significant.
reducer is acceptable for dynamic modulus tests in the SPT. Table 28 presents the results for the unconfined tests, while
Table 29 presents the results for the confined tests. The sec-
tions that follow discuss the results for the flow number and
2.3 Flow Number Test the measured permanent strains.
The results of the flow number ruggedness testing are pre-
sented in Appendix B. The flow number ruggedness experi- 2.3.1 Factors Affecting Flow Number
ment included the factors listed in Table 7. The responses
measured in the flow number ruggedness experiment included In order to analyze the flow number, all specimens tested
the flow number and the permanent strain after selected num- in both laboratories must exhibit flow. Flow occurred in all of
ber of load cycles. Flow did not occur in all of the confined the unconfined tests on the dense-graded mixture and about
tests. Table 21 summarizes the data that was analyzed for the 25 percent of the confined tests on the dense-graded mixture.
flow number tests.
Regression equations of the form of Equation 1 were de- Table 23. Significance of flow number ruggedness
veloped for each of the marked cells in Table 21. The results test factors for unconfined tests with the IPC SPT
on the dense mixture.
Permanent Strain at
Table 21. Flow number test data. Flow 500 1000 2000
Factors Number cycles cycles cycles
Parameter Dense Dense SMA
Equilibrium Temperature (-1 vs +1 C) 0.03 0.31 0.23 0.33
Unconfined Confined Confined
Flow Number X Transfer time (3 vs 5 min) 0.76 0.14 0.26 0.44
p at 500 cycles X X X Conditioning Fluid (Water vs Air) 0.74 0.22 0.15 0.18
p at 1000 cycles X X X End Condition (Mill vs Saw) 0.99 0.07 0.26 0.79
p at 2000 cycles X X X Friction Reducer (Teflon vs Latex) 0.39 0.29 0.25 0.22
p at 5000 cycles X Axial Stress (135 vs 145 kPa) 0.98 0.77 0.74 0.64
p at 8000 cycles X Dwell Time (0.85 vs 0.95 sec) 0.30 0.69 0.67 0.55

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Table 24. Significance of flow number ruggedness Table 28. Significance of flow number ruggedness
test factors for confined tests with the ITC SPT test factors on unconfined tests.
on the dense mixture.
Flow 500 1000 2000
Permanent Strain at Factors Number cycles cycles cycles
Flow 500 1000 2000 Equilibrium Temperature (-1 vs +1 C) 100 0 0 50
Factors Number cycles cycles cycles Transfer time (3 vs 5 min) 0 0 0 0
Equilibrium Temperature (-1 vs +1 C) 0.02 0.01 0.00 Conditioning Fluid (Water vs Air) 0 50 50 50
Transfer time (3 vs 5 min) 0.14 0.07 0.02 End Condition (Mill vs Saw) 0 100 50 50
Conditioning Fluid (Water vs Air) 0.37 0.43 0.53 Friction Reducer (Teflon vs Latex) 50 0 0 50
End Condition (Mill vs Saw) 0.12 0.12 0.05 Axial Stress (135 vs 145 kPa) 0 0 0 0
Friction Reducer (Teflon vs Latex) 0.01 0.00 0.00 Contact Stress (5 vs 10 kPa)1 0 0 0 0
Axial Stress (945 vs 985 kPa) 0.07 0.05 0.02 Dwell2 0 0 0 0
Confining Stress (135 vs 145 kPa) 0.21 0.09 0.02 Notes:
1
ITC only
2
IPC only
Table 25. Significance of flow number ruggedness None of the SMA specimens exhibited flow in the confined
test factors for confined tests with the IPC SPT tests.
on the dense mixture. Only temperature and end friction reducer were found to
Permanent Strain at have a statistically significant effect on the flow number in un-
Flow 500 1000 2000 confined tests. Figure 12 shows the effect of these two factors.
Factors Number cycles cycles cycles For temperature the flow number decreases by 7.5 percent for
Equilibrium Temperature (-1 vs +1 C) 0.45 0.32 0.26
an increase in temperature of 0.5°C while the flow number is
Transfer time (3 vs 5 min) 0.39 .030 0.28
Conditioning Fluid (Water vs Air) 0.58 0.82 0.95
20 percent higher when TeflonTM is used as the end friction
End Condition (Mill vs Saw) 0.01 0.06 0.23 reducer. As expected, increasing temperature decreases the
Friction Reducer (Teflon vs Latex) 0.08 0.10 0.11 flow number. Apparently the TeflonTM end friction reducer is
Axial Stress (945 vs 985 kPa) 0.79 0.56 0.46 less effective than the greased latex membranes resulting in
Confining Stress (135 vs 145 kPa) 0.35 0.39 0.41 greater end friction and a higher flow number.
Table 26. Significance of flow number ruggedness test factors
for confined tests with the ITC SPT on the SMA mixture.
Permanent Strain at
Flow 500 1000 2000 5000 8000
Factors Number cycles cycles cycles cycles cycles
Equilibrium Temperature (-1 vs +1 C) 0.29 0.33 0.48 0.88 0.87
Transfer time (3 vs 5 min) 0.34 0.35 0.38 0.34 0.40
Conditioning Fluid (Water vs Air) 0.79 0.94 0.88 0.75 0.59
End Condition (Mill vs Saw) 0.77 0.94 0.92 0.80 0.71
Friction Reducer (Teflon vs Latex) 0.02 0.07 0.21 0.42 0.42
Axial Stress (945 vs 985 kPa) 0.88 0.85 0.68 0.74 0.98
Confining Stress (135 vs 145 kPa) 0.25 0.25 0.37 0.65 0.37
Table 27. Significance of flow number ruggedness test factors
for confined tests with the IPC SPT on the SMA mixture.
Permanent Strain at
Flow 500 1000 2000 5000 8000
Factors Number cycles cycles cycles cycles cycles
Equilibrium Temperature (-1 vs +1 C) 0.70 0.71 0.52 0.63 0.77
Transfer time (3 vs 5 min) 0.84 0.86 0.50 0.31 0.41
Conditioning Fluid (Water vs Air) 0.98 0.40 0.26 0.49 0.80
End Condition (Mill vs Saw) 0.71 0.82 0.93 0.66 0.89
Friction Reducer (Teflon vs Latex) 0.00 0.00 0.01 0.08 0.07
Axial Stress (945 vs 985 kPa) 0.19 0.24 0.28 0.48 0.74
Confining Stress (135 vs 145 kPa) 0.05 0.05 0.14 0.40 0.53