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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
REPORT 
This report is an archived publication and may contain dated technical, contact, and link information 

Publication Number: FHWAHRT11045 Date: November 2012 
Publication Number: FHWAHRT11045 Date: November 2012 
This chapter brings together fullscale ALF performance and laboratory mixture performance to assess the strengths and weaknesses of the various candidate binder parameters. The same composite statistical scoring technique is applied using diversified statistical measures, including slope regression significance (probability), Kendall’s tau measure of association and its associated significance (probability), and conventional correlation coefficient.
As previously discussed, the first measure of appropriateness for any binder or mixture laboratory test is whether the trends in the relationship are in the correct proportional or inverse direction. An extra step is needed to inspect the trends of the binder parameter with mixture performance and fullscale ALF performance because a composite score from the two will be utilized. It is possible, depending on the scatter in the data, that one of the two would be correct. Ideally, both should be correct. Table 100 lists the hightemperature binder rutting parameters and the corresponding laboratory mixture performance and ALF performance data that are compared for the 4inch (100mm) lanes. Table 101 lists the same for the 5.8inch (150mm) lanes. The slope of the linear regression was checked to screen relationships between binder parameters, mixture performance, and ALF performance to identify scenarios that should or should not receive continued analysis for the statistical composite score.
Binder Parameter 
Comparative Performance Data 
Expected Trend 
Correct Trend? 

G*/sinδ at 10 radians/s 
69/827 kPa flow number, ALF voids permanent strain at 5,000 cycles 
Inverse 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Inverse 
Yes 

G*/sinδ at 0.25 radians/s 
69/827 kPa flow number, ALF voids Permanent strain at 5,000 cycles 
Inverse 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Inverse 
Yes 

Nonrecovered compliance 3,200 Pa 
69/827 kPa flow number, ALF voids Permanent strain at 5,000 cycles 
Proportional 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Proportional 
Yes 

Oscillatorybased surrogate for nonrecovered compliance 
69/827 kPa flow number, ALF voids Permanent strain at 5,000 cycles 
Inverse 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Inverse 
Yes 

ZSV 
69/827 kPa flow number, ALF voids Permanent strain at 5,000 cycles 
Inverse 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Inverse 
Yes 

LSV 
69/827 kPa flow number, ALF voids Permanent strain at 5,000 cycles 
Inverse 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Inverse 
Yes 

MVR 
69/827 kPa flow number, ALF voids Permanent strain at 5,000 cycles 
Proportional 
Yes 
100 mm ALF rut depth at 25,000 cycles 
Proportional 
Yes 
1 Pa = 0.000145 psi
1 mm = 0.039 inches
Binder Parameter 
Comparative Performance Data 
Expected Trend 
Correct Trend? 

G*/sinδ at 10 radians/s 
69/523 kPa flow number, fixed voids Permanent strain at 20,000 cycles 
Inverse 
Yes 
150 mm ALF rut depth at 25,000 cycles 
Inverse 
No 

G*/sinδ at 0.25 radians/s 
69/523 kPa flow number , fixed voids Permanent strain at 20,000 cycles 
Inverse 
Yes 
150 mm ALF rut depth at 25,000 cycles 
Inverse 
No 

Nonrecovered compliance 3,200 Pa 
69/523 kPa flow number, fixed voids Permanent strain at 20,000 cycles 
Proportional 
Yes 
150 mm ALF rut depth at 25,000 cycles 
Proportional 
No 

Oscillatorybased surrogate for nonrecovered compliance 
69/523 kPa flow number, fixed voids Permanent strain at 20,000 cycles 
Inverse 
No 
150 mm ALF rut depth at 25,000 cycles 
Inverse 
No 

ZSV 
69/523 kPa flow number, fixed voids Permanent strain at 20,000 cycles 
Inverse 
No 
150 mm ALF rut depth at 25,000 cycles 
Inverse 
No 

LSV 
69/523 kPa flow number, fixed voids Permanent strain at 20,000 cycles 
Inverse 
No 
150 mm ALF rut depth at 25,000 cycles 
Inverse 
No 

MVR 
69/523 kPa flow number, fixed voids Permanent strain at 20,000 cycles 
Proportional 
Yes 
150 mm ALF rut depth at 25,000 cycles 
Proportional 
Yes 
1 Pa = 0.000145 psi
1 mm = 0.039 inches
The relationships in table 100 to evaluate rutting in the 4inch (100mm) ALF lanes were all correct, and the relationships still held when the data points for lane 6 (terpolymer) and associated binder and mixture tests were removed. There were intermixed correct and incorrect trends for the rutting in the 5.8inch (150mm) ALF lanes. These results may seem surprising; however, the appearance of incorrect scenarios for the 5.8inch (150mm) ALF rutting does not signify poor or weak binder parameters. Rather, it is a direct reflection of the lack of variety in 5.8inch (150‑mm) ALF rutting (see table 19 and figure 29 in chapter 3). This point puts the analysis at an impasse but is also an indicator of a very successful experimental design that targeted binders having equivalent hightemperature performance specifications but different intermediatetemperature performance specifications associated with fatigue cracking. This further suggests that the standard Superpave^{®} hightemperature specification is valid, at least for the materials in this research study, given that the materials were selected for the experimental design using the Superpave^{®} hightemperature rutting parameter. In other words, there could be an underlying relationship that identifies stronger or weaker parameters than Superpave^{®}, but the characteristics of the data simply cannot do so (see discussion in chapter 3 on capturing trends in light of scatter and number of data points).
The culmination of the numerical and statistical identification of the strongest and weakest binder parameters for rutting and permanent deformation are found in table 102 for all of the applicable 4inch (100mm) ALF lanes and in table 103 eliminating lane 6 (terpolymer). The entire composite score and each of the statistical components (regression slope significance, Kendall’s tau measure of association, significance of Kendall’s tau score, and correlation coefficient) used to compute the composite score are provided in the tables.
Binder Test for Rutting 
Comparative Data 
1p_{Reg} 
t_{K} 
1p_{tK }(percent) 
R 
Composite Score 

LSV 
Flow number 
95 
1.00 
99 
0.87 
0.81 
ALF rutting 
82 
0.40 
76 
0.71 

ZSV 
Flow number 
94 
1.00 
99 
0.87 
0.81 
ALF rutting 
82 
0.40 
76 
0.71 

MSCR nonrecovered compliance 
Flow number 
99 
1.00 
99 
0.97 
0.72 
ALF rutting 
37 
0.40 
76 
0.29 

Oscillatorybased nonrecovered stiffness 
Flow number 
88 
0.8 
96 
0.78 
0.69 
ALF rutting 
71 
0.2 
59 
0.59 

G*/sinδ at 0.25 radians/s 
Flow number 
89 
0.40 
76 
0.79 
0.63 
ALF rutting 
78 
0.20 
59 
0.66 

MVR 
Flow number 
77 
0.60 
88 
0.66 
0.59 
ALF rutting 
35 
0.40 
76 
0.28 

G*/ sinδ at 10 radians/s 
Flow number 
59 
0.20 
59 
0.48 
0.56 
ALF rutting 
81 
0.40 
76 
0.69 
Binder Test for Rutting 
Comparative Data 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

LSV 
Flow number 
88 
1.00 
96 
0.88 
0.90 
ALF rutting 
98 
0.67 
83 
0.98 

ZSV 
Flow number 
89 
1.00 
96 
0.89 
0.89 
ALF rutting 
95 
0.67 
83 
0.95 

Oscillatorybased nonrecovered stiffness 
Flow number 
78 
1.00 
96 
0.78 
0.87 
ALF rutting 
95 
0.67 
83 
0.95 

MSCR nonrecovered compliance 
Flow number 
99 
1.00 
96 
0.99 
0.86 
ALF rutting 
73 
0.67 
83 
0.73 

G*/sinδ at 0. 
Flow number 
80 
0.67 
83 
0.80 
0.73 
ALF rutting 
90 
0.33 
63 
0.90 

MVR 
Flow number 
68 
0.33 
63 
0.68 
0.68 
ALF rutting 
82 
0.67 
83 
0.82 

G*/ sinδ at 10 radians/s 
Flow number 
56 
0.33 
63 
0.56 
0.44 
ALF rutting 
52 
0.00 
38 
0.52 
That the ranking of the strongest to weakest binder parameters did not essentially change whether the data points from lane 6 were included or excluded was somewhat unexpected. When the lane 6 terpolymer was removed, the stronger parameters became stronger and the weaker parameters became weaker. The rank order of the oscillatorybased nonrecovered stiffness and MSCR switched, but their scores were nearly identical in each comparison.
LSV and ZSV were the strongest statistical parameters associated with laboratory and fullscale rutting. The weakest was the standard Superpave^{®} parameter, which is counter to the alternative interpretation of ALF performance and experimental design because the binders were chosen based on the same Superpave^{®} hightemperature PG and exhibited statistically equivalent rutting. The next two strongest parameters quantify nonrecoverable deformation by different means; MSCR is a direct quantification while the oscillatorybased parameter is indirect but based on theoretical derivation and confirmed by comparison with direct MSCR. The variation of the standard Superpave^{®} parameter taken at a 0.25 radians/s frequency did better than the standard parameters taken at 10 radians/s, likely because of the intent to emphasize the softer portion of the binder response with polymer modification. MVR did better than the standard Superpave^{®} parameters but not as well as the modified, lower frequency Superpave^{®} parameter.
The quantitative ranking of the strongest and weakest parameters is important, but not a complete deciding factor in and of itself. Specification tests should ideally be both discriminating but also practical for broader use by the asphalt binder supply industry, contractors, and owner agencies. It is challenging to score and quantitatively rank the implementability of the candidate specifications. Qualitative consideration of various caveats associated with each test is provided to help further narrow down recommended specifications.
ZSV and LSV were identified as the strongest parameters, and both can be conducted in DSR equipment already implemented by Superpave^{®}. ZSV can require a long time for each test, and LSV offers an improvement by speeding up the process. Both of these computed viscosities correctly reflected the beneficial contributions of polymer modification. However, these parameters are still a physical measure of viscosity in which apparent improvements can be achieved by means of stiffening from fillers or polyphosphoric acid, which do not impart comparable performanceimproving characteristics of polymer modification. This research further confirms the MVR as a valid alternative to the Superpave^{®} hightemperature PG, but the development and application of the MVR was intended as a rapid verification of PG grade. This leaves the two parameters that measure nonrecoverable deformations, and both can be measured using DSR. The profession may be able to relate with oscillatorybased nonrecoverable stiffness more than MSCR because it is based on the same properties currently measured for PG grade: G* shear modulus and the phase angle δ. On the other hand, MSCR has advantages over the oscillatorybased nonrecoverable stiffness because MSCR provides an additional measure of the recoverable deformation by means of percent recovery, which AASHTO TP 70 integrates.^{(73)}
The various candidate intermediatetemperature binder fatigue parameters were also compared against both laboratory fatigue tests and fullscale ALF fatigue cracking. The comparisons of binder with ALF performance and binder with the straincontrolled axial cyclic fatigue test selected in the previous chapter were combined into a single composite score to identify stronger and weaker tests for discriminating fatigue cracking. Table 104 summarizes the checks that were conducted to make sure that both the axial fatigue test and the 4inch (100mm) ALF fatigue cracking had the same trend and correct direction, whether an inverse relationship or proportional relationship. All binder tests provided the correct trend except the binder stress sweep fatigue test, which had the opposite ranking. When the trends were checked using the 5.8inch (150mm) ALF lanes and associated laboratory mixture tests, only CTOD, failure strain in lowtemperature DT test, large strain time sweep surrogate, and Superpave^{®} G*sinδ had correct trends. Binder yield energy was not present, probably due to data scatter and the number of data points. More binder tests exhibited correct trends when SBS 6440 data, which challenged the laboratory fatigue characterization ranking, were removed.
Binder Parameter 
Comparative Performance Data 
Expected Trend 
Correct Trend? 

G*sinδ 
N_{F} strain control axial fatigue + VECD 
Inverse 
Yes 
Cycles to 25 percent cracked area 
Inverse 
Yes 

DTT failure strain 
N_{F} strain control axial fatigue + VECD 
Proportional 
Yes 
Cycles to 25 percent cracked area 
Proportional 
Yes 

BBR mvalue 
N_{F} strain control axial fatigue + VECD 
Proportional 
Yes 
Cycles to 25 percent cracked area 
Proportional 
Yes 

Time sweep N_{F} 
N_{F} strain control axial fatigue + VECD 
Proportional 
Yes 
Cycles to 25 percent cracked area 
Proportional 
Yes 

Stress sweep N_{F} 
N_{F} strain control axial fatigue + VECD 
Proportional 
No 
Cycles to 25 percent cracked area 
Proportional 
No 

Large strain time sweep surrogate 
N_{F} strain control axial fatigue + VECD 
Inverse 
Yes 
Cycles to 25 percent cracked area 
Inverse 
Yes 

EWF 
N_{F} strain control axial fatigue + VECD 
Proportional 
Yes 
Cycles to 25 percent cracked area 
Proportional 
Yes 

CTOD 
N_{F} strain control axial fatigue + VECD 
Proportional 
Yes 
Cycles to 25 percent cracked area 
Proportional 
Yes 

Binder yield energy 
N_{F} strain control axial fatigue + VECD 
Proportional 
Yes 
Cycles to 25 percent cracked area 
Proportional 
Yes 
Table 105 ranks the binder parameters from strongest to weakest based on the composite score corresponding to the fatigue cracking performance in the 4inch (100mm) ALF lanes. The individual components for each axial fatigue and ALF comparison used to calculate the score (regression slope significance, Kendall’s tau measure of association, significance of the Kendall’s tau score, and correlation coefficient) are provided as well. The ranking reveals that there are more discriminating parameters than the Superpave^{®} G*sinδ. CTOD has the strongest association with laboratory and fullscale ALF fatigue cracking followed by the binder yield energy. Both of these parameters mobilize the binder to very large strains and deformations, which research has identified as a needed mechanism to capture the beneficial effects from polymer modification. Number of cycles to failure from the time sweep cyclic fatigue test is the third strongest parameter and takes place at a smaller strain, but the approach illustrates that cyclic fatigue on binder and cyclic fatigue on mixture are equally valid. Brittle failure strain in DT at temperatures much lower than the intermediate fatigue region discriminates fatigue cracking better than the standard Superpave^{®} fatigue parameter for these particular mixes, which reinforces using deformations larger than are applied in Superpave^{®} G*sinδ. The weaker parameters identified were the creep slope mvalue from BBR and EWF. BBR mvalue was identified in the literature review as worthy of exploration but did not appear to provide any discrimination with the materials in this experiment, possibly due the small deformations and lowtemperature region. The weaker EWF is a necessary step in the calculation of CTOD by means of the yield strength. This suggests the contributions of yield strength to EWF to compute CTOD is important.
Binder Test for Fatigue Cracking 
Comparative Data 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

CTOD 
Axial fatigue 
99 
1.00 
99 
0.95 
0.99 
ALF cracking 
100 
1.00 
99 
0.98 

Binder yield energy 
Axial fatigue 
94 
0.80 
96 
0.87 
0.88 
ALF cracking 
90 
0.80 
99 
0.80 

Time sweep 
Axial fatigue 
89 
0.80 
96 
0.79 
0.88 
ALF cracking 
95 
0.80 
96 
0.88 

Failure strain in lowtemperature DT test 
Axial fatigue 
92 
0.60 
88 
0.83 
0.81 
ALF cracking 
93 
0.60 
88 
0.85 

Superpave^{®} G*sinδ 
Axial fatigue 
84 
0.60 
88 
0.73 
0.75 
ALF cracking 
78 
0.60 
88 
0.66 

Large strain time sweep surrogate 
Axial fatigue 
85 
0.40 
76 
0.74 
0.67 
ALF cracking 
78 
0.40 
76 
0.67 

EWF 
Axial fatigue 
53 
0.40 
76 
0.43 
0.55 
ALF cracking 
60 
0.40 
76 
0.50 

mvalue from lowtemperature BBR 
Axial fatigue 
63 
0.40 
76 
0.52 
0.54 
ALF cracking 
47 
0.40 
76 
0.38 

Stress sweep 
Axial fatigue 
89 
0.40 
76 
0.79 
0.69* 
ALF cracking 
83 
0.40 
76 
0.73 
*Incorrect trend direction
The results from the ranking analysis corresponding to the 5.8inch (150mm) ALF lanes with and without lane 9 (SBS 6440) are shown in table 106 and table 107, respectively. Consistent with the previous ranking, CTOD and binder yield energy are present at the top, which further supports the discriminating ability of these tests.
Binder Test for Fatigue Cracking 
Comparative Data 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

CTOD 
Axial fatigue 
96 
0.80 
96 
0.89 
0.62 
ALF cracking 
12 
0.40 
76 
0.10 

Failure strain in lowtemperature DT test 
Axial fatigue 
94 
0.60 
88 
0.86 
0.55 
ALF cracking 
16 
0.20 
59 
0.13 

Large strain time sweep surrogate 
Axial fatigue 
78 
0.80 
96 
0.67 
0.54 
ALF cracking 
38 
0.00 
41 
0.30 

Superpave^{®} G*sinδ 
Axial fatigue 
74 
0.80 
96 
0.63 
0.53 
ALF cracking 
38 
0.00 
41 
0.31 
Binder Test for Fatigue Cracking 
Comparative Data 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

Binder yield energy 
Axial fatigue 
79 
1.00 
96 
0.79 
0.83 
ALF cracking 
79 
0.67 
83 
0.79 

CTOD 
Axial fatigue 
29 
0.67 
83 
0.29 
0.75 
ALF cracking 
100 
1.00 
96 
1.00 

Large strain time sweep surrogate 
Axial fatigue 
68 
0.67 
83 
0.68 
0.64 
ALF cracking 
65 
0.33 
63 
0.65 

Superpave^{®} G*sinδ 
Axial fatigue 
67 
0.67 
83 
0.67 
0.63 
ALF cracking 
61 
0.33 
63 
0.61 

Failure strain in lowtemperature DT test 
Axial fatigue 
24 
0.33 
96 
0.24 
0.39 
ALF cracking 
21 
0.33 
63 
0.21 
A collaborative effort between the Ontario Ministry of Transport, Ontario Hot Mix Asphalt Producers, and Queens University built pavement test sections to understand the influence of asphalt binder specifications on lowtemperature thermal cracking. These test sections were similar to the ALF fullscale accelerated pavement experimental design because the mix design and construction were the same, and the only variable was asphalt binder. An overview of the binders used and physical properties measured by Queens University and TFHRC is provided in table 108.^{(104)} The binders were characterized for CTOD, binder yield energy, and Superpave^{®} G*sinδ. The materials and performance data from the Ontario experiment offer an opportunity to explore CTOD and binder yield energy because cracking other than classical lowtemperature thermal cracking appeared.
Binder 
Superpave^{®} G*sinδ (kPa)^{(105)} 
CTOD 25 °C 
Binder Yield Energy 15 °C (TFHRC)(Pa) 


16 °C 
25 °C 

A 
Terpolymer (Elvaloy^{®}) 
2,218 
550 
16 
399.5 
B 
Oxidized + SBS 
2,588 
860 
10 
822.5 
C 
SBS 
1,954 
670 
15 
365 
D 
SBS 
2,226 
690 
13 
504 
E 
SBS 
2,273 
590 
38 
499 
F 
Oxidized 
1,820 
690 
7 
818.5 
G 
Unmodified 
1,542 
350 
10 
302.5 
1 Pa = 0.000145 psi
°F = 1.8(°C) + 32
1 mm = 0.039 inches
Detailed crack maps provided by the Ontario Ministry of Transportation were used to classify cracking into longitudinal, centerline, edge, alligator, and transverse after 5 years of service (2003–2008).^{(105)} It has been reported that the southbound traffic contained trucks having heavier loads than the northbound traffic because southbound trucks are returning from logging activities. Significantly different amounts of cracking are found in the two directions. This performance suggests that the difference between cracking in the northbound and southbound lanes could be loadassociated cracking rather than lowtemperature thermal cracking. Some limited alligator fatigue cracking appeared, but some short transverse cracking limited to within the wheel paths could be the beginning of interconnected alligator fatigue cracking.^{(104)} The total number of cracks, total length of cracks, and length of longitudinal cracks are provided in table 109 through and table 111, respectively. The tables do not contain any centerline cracking. The ranking changes slightly depending on the type of cracking.
Section 
Total Number of Individual Cracks 
Difference in Cracks 


Northbound 
Southbound 

D 
91 
199 
108 
F 
25 
89 
64 
G 
77 
125 
48 
C 
27 
51 
24 
B 
43 
59 
16 
E 
12 
23 
11 
A 
3 
4 
1 
Section 
Total Length of All Cracks (m) 
Difference All Crack Length (m) 


Northbound 
Southbound 

G 
76.9 
239.7 
162.8 
B 
76.4 
154.3 
77.9 
F 
19.8 
66.6 
46.8 
C 
41.4 
76.7 
35.3 
D 
229.9 
257.3 
27.4 
A 
4 
8.1 
4.1 
E 
34.9 
32.5 
(2.4) 
1 m = 3.28 inches
Section 
Total Length of Transverse Cracks (m) 
Difference Long. Crack Length (m) 


Northbound 
Southbound 

D 
47.3 
92.5 
45.2 
C 
17.6 
33.8 
16.2 
G 
22.6 
37.6 
15 
F 
13.4 
28.1 
14.7 
E 
1.1 
3.2 
2.1 
B 
18.1 
20.1 
2 
A 
0 
0.3 
0.3 
1 m = 3.28 inches
Again, the previously described statistical scoring was used, except only binder properties were compared against the fullscale highway test section cracking. The rankings of three binder tests are provided in table 112 through table 114 for the comparisons with the total number of cracks, total lengths of cracks, and length of transverse cracks, respectively. Although the results are weaker than ALF, CTOD has the strongest association with the observed cracking while the binder yield energy and Superpave^{®} G*sinδ are weaker and sometimes have incorrect trends altogether. These results, combined with the ALF results, help further identify and confirm that CTOD is a discriminating parameter for fatigue cracking.
Binder Test 
Expected Trend 
Correct 
Regression Slope 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

CTOD 
Inverse 
Yes 
(–) 
63% 
0.43 
88% 
0.41 
0.59 
G*sinδ 25 °C 
Proportional 
Yes 
(+) 
7% 
0.24 
72% 
0.04 
0.27 
Binder yield energy 
Inverse 
No 
(+) 
18% 
0.05 
50% 
0.10 
0.21 
G*sinδ 16 °C 
Proportional 
No 
(–) 
46% 
0.24 
72% 
0.28 
0.42 
°F = 1.8(°C) + 32
Binder Test 
Expected Trend 
Correct 
Regression Slope 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

CTOD 
Inverse 
Yes 
(–) 
79% 
0.62 
97% 
0.54 
0.73 
Binder yield energy 
Inverse 
No* 
(–) (+) 
18% 
0.05 
50% 
0.11 
0.21 
G* sinδ 25 °C 
Proportional 
No** 
(–) 
63% 
0.24 
72% 
0.40 
0.50 
G*sinδ 16 °C 
Proportional 
No 
(–) 
80% 
0.43 
88% 
0.55 
0.66 
°F = 1.8(°C) + 32
*Somewhat.
**Mostly.
Binder Test 
Expected Trend 
Correct 
Regression Slope 
1p_{Reg} 
t_{K} 
1p_{tK} 
R 
Composite Score 

CTOD 
Inverse 
Yes 
(–) 
50% 
0.05 
50% 
0.31 
0.34 
Binder yield energy 
Inverse 
Yes 
(–) 
22% 
0.14 
61% 
0.13 
0.28 
G* sinδ 25 °C 
Proportional 
Yes 
(+) 
6% 
0.05 
50% 
0.04 
0.16 
G*sinδ 16 °C 
Proportional 
No 
(–) 
35% 
0.24 
72% 
0.21 
0.38 
°F = 1.8(°C) + 32
The strongest binder parameters identified in table 105 as being better that Superpave^{®} G*sinδ are the CTOD, binder yield energy, time sweeps, and lowtemperature DT failure strain. The advantage of binder yield energy is that it can be measured in the DSR. However, University of Wisconsin researchers have recently postponed further development of this test in favor of alternative strain sweep characterization procedures that take advantage of VECD methodologies because of one particular shortcoming with the binder yield energy test: some modified binder exhibit two peaks (initial yield and ultimate yield) in the binder yield energy test, which presents a challenge as to when and where the strain energy is to be calculated (see figure 119). The VECDbased stress sweep binder test was outside the scope of this study at the time this report was written. Lowtemperature failure strain was the next strongest parameter. Although lowtemperature DT testing combined with BBR testing provides a more rigorous lowtemperature PG grade than BBR alone, DT testing has already fallen out of favor by agencies. If this was to be reconsidered for fatigue resistance, the failure strain alone is likely vulnerable to not appropriately catching fatigue and cracking resistance because softer or lowerquality binders could exhibit higher strain tolerance. This was not the case for the legitimate, highquality binders in this study. DT test failure strain would have to be accompanied with a strength measurement that the DT test can provide, but DENT testing at intermediate temperatures for CTOD is already a type of tension test where extension and strength are measured. Nonetheless, the largest hurdle for implementation of CTOD using DENT is the need for a new piece of test equipment if a laboratory does not already have one to measure forceductility (AASHTO T 300).^{(106)} Ruggedness evaluation of existing AASHTO T 300 equipment for measuring CTOD would be a necessary next step.