comparison of typical dynamic modulus for hot mix asphalt ...sspco.com/docs/npv/2182.pdf · ......

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The above chart references data from a report by Peter Sebaaly, Ph.D., P.E. University of Nevada, Reno, Director of the Western Regional Superpave Center. The original charts are provided on the following pages of this document.

COMPARISON OF TYPICAL DYNAMIC MODULUS FOR HOT MIX

ASPHALT (HMA) MIXTURE AND NATURALPAVE® XL RESIN PAVEMENT™

Dynamic modulus is the main input required for design of Hot Mix Asphalt (HMA) pavements using the nationally recognized AASHTO Mechanistic-Emperical Pavement Design Guide (MEPDG). HMA pavement materials are viscoelastic in nature and their dynamic modulus values vary dramatically in response to changes in loading rate

and temperature. For example, HMA materials exhibit much lower dynamic modulus values (significant strength loss) as pavement temperatures increase. In contrast, the impact of changes in loading rate and temperature on the dynamic modulus of the NaturalPAVE XL Resin Pavement material is only moderate and good strength values are retained at all loading rates and temperatures. While retaining viscoelastic behavior, cold-mixed NaturalPAVE XL Resin Pavement materials have the further advantage of gaining strength with additional curing time.

Results after 72 Hours of curing Results after 168 Hours of curing Results after 720 Hours of curing

Stron

ger

Hotter

ASPHALT

NATURALPAVE

70°F

ASPHALT

NATURALPAVE

100°F

ASPHALT

NATURALPAVE

130°F

ASPHALT

NATURALPAVE

40°F

ASPHALT

NATURALPAVE

28.4°F

Dyn

amic

Mod

ulus

(E*)

, ksi

200

600

1200

16

00

2000

24

00

2800

40

0 80

0 14

00

1800

22

00

2600

30

00

1000

7

Figure 7. Typical Dynamic Modulus Data for HMA Mixture.

Figures 8, 9, and 10 compare the magnitude of the E* property at various temperatures and loading frequency of the NaturalPAVE mixture at the three curing stages. The bars in Figures 8 – 10 represent the average E* values while the whiskers on top of the bars represent the limits of the 95% confidence interval (CI) of the measured E* property. An examination of the data in Figures 8 – 10 leads to the following two conclusions:

The magnitude of the E* at the three curing conditions is impacted by temperature and frequency of loading indicating a visco-elastic behavior of the NaturalPAVE mixture. Therefore, the E* master curve is the appropriate property to characterize the stiffness of the NaturalPAVE mixture in a mechanistic pavement design.

The variations of the measured E* properties among the three replicates is minimal. Therefore, an average E* of the three replicates can be used to represent the stiffness of the NaturalPAVE mix at any combination of temperature and frequency of loading.

Figure 11 compares the master curves of the NaturalPAVE mixtures at the three curing conditions. Examination of the data presented in Figure 11 leads to the following observations:

The E* property of the NaturalPAVE mix significantly increases as the curing period is increased from 72 to 168 hrs at all combinations of temperature and frequency of loading. However, the rate of increase in the E* property is significantly reduced as the curing period is increased from 168 to 720 hrs. This indicates that the aging process of the NaturalPAVE mix slows down significantly after the 168 hrs period. This is

1

10

100

1000

10000

0.1 1 10 100

Dyna

mic

Mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

7

Figure 7. Typical Dynamic Modulus Data for HMA Mixture.

Figures 8, 9, and 10 compare the magnitude of the E* property at various temperatures and loading frequency of the NaturalPAVE mixture at the three curing stages. The bars in Figures 8 – 10 represent the average E* values while the whiskers on top of the bars represent the limits of the 95% confidence interval (CI) of the measured E* property. An examination of the data in Figures 8 – 10 leads to the following two conclusions:

The magnitude of the E* at the three curing conditions is impacted by temperature and frequency of loading indicating a visco-elastic behavior of the NaturalPAVE mixture. Therefore, the E* master curve is the appropriate property to characterize the stiffness of the NaturalPAVE mixture in a mechanistic pavement design.

The variations of the measured E* properties among the three replicates is minimal. Therefore, an average E* of the three replicates can be used to represent the stiffness of the NaturalPAVE mix at any combination of temperature and frequency of loading.

Figure 11 compares the master curves of the NaturalPAVE mixtures at the three curing conditions. Examination of the data presented in Figure 11 leads to the following observations:

The E* property of the NaturalPAVE mix significantly increases as the curing period is increased from 72 to 168 hrs at all combinations of temperature and frequency of loading. However, the rate of increase in the E* property is significantly reduced as the curing period is increased from 168 to 720 hrs. This indicates that the aging process of the NaturalPAVE mix slows down significantly after the 168 hrs period. This is

1

10

100

1000

10000

0.1 1 10 100

Dyna

mic

Mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F




Dynamic Modulus for the NaturalPAVE Mixture Cured for 72 hours

Typical Dynamic Modulus Data for Hot Mix Asphalt (HMA) Mixture



5

Figure 3. NaturalPAVE Sample in Dynamic Modulus testing Set-up.

Figure 4. Dynamic Modulus for the NaturalPAVE Mixture Cured for 72 hours at 104oF.

10

100

1000

10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°FFigure 4

Figure 7

The above figures are from a report by Peter Sebaaly, Ph.D., P.E. University of Nevada, Reno, Director of the Western Regional Superpave Center.








6



10

100

1000

10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

10

100

1000

10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

6



10

100

1000

10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

10

100

1000

10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

6



10

100

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10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

10

100

1000

10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

6



10

100

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10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

10

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10000

0.1 1 10 100

Dyna

mic

mod

ulus

|E*

|, k

si

Frequency, Hz

28.4°F 40°F 70°F 100°F 130°F

Figure 5

Figure 6







Typical E* Master Curve for a HMA Mix

4

Dynamic Modulus Set-Up Applied Stress & Measured Strain

Dynamic Modulus

Typical E* Master Curve

Figure 2. Components of the Dynamic Modulus Test and a Typical E* Master Curve for a HMA

Mix.

1

10

100

1,000

10,000

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz

14°F 40°F 70°F 100°F 130°F Predicted E*

Time

Strain

Time

time shift = φ

= 0sin(ωt)

0

0

= 0sin(ωt-φ)

Stress

0

0*E

4


Dynamic Modulus



Mix.

1

10

100

1,000

10,000

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz


Time

Strain

Time

time shift = φ

= 0sin(ωt)

0

0

= 0sin(ωt-φ)

Stress

0

0*E

Frequency, Hz

Dynamic Modulus Master Curves for the NaturalPAVE Mix

10


Figure 11. Dynamic Modulus Master Curves for the NaturalPAVE Mixture Cured for 72, 168, and 720 hours at 104oF.

0

500

1000

1500

2000

2500

3000

2510510.50.1

Dyna

mic

Mod

ulus

|E*

|, k

si

Frequency (Hz)

28.4°F 40°F 70°F 100°F 130°F

1

10

100

1000

10000

1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz

E* after 3days curing at 104F E* after 7days curing at 104F E* after 30days of curing at 104F

10


Figure 11. Dynamic Modulus Master Curves for the NaturalPAVE Mixture Cured for 72, 168, and 720 hours at 104oF.

0

500

1000

1500

2000

2500

3000

2510510.50.1

Dyna

mic

Mod

ulus

|E*

|, k

si

Frequency (Hz)

28.4°F 40°F 70°F 100°F 130°F

1

10

100

1000

10000

1.E-07 1.E-05 1.E-03 1.E-01 1.E+01 1.E+03 1.E+05 1.E+07

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz

E* after 3days curing at 104F E* after 7days curing at 104F E* after 30days of curing at 104FFrequency, Hz

The American Association of State Highway Transportation Officials (AASHTO) has developed a nationally recognized pavement design system known as the AASHTO Mechanistic - Empirical

Pavement Design Guide (MEPDG). Dynamic Modulus testing is used to evaluate viscoelastic pavement materials such as Hot Mix Asphalt (HMA) and NaturalPAVE XL Resin Pavement. The variations in pavement material behavior related to various combinations of loading frequency and temperature are then presented for each pavement material as a Dynamic Modulus (E*) Master Curve. The cold-mixed NaturalPAVE XL Resin Pavement gains strength over time as illustrated by the three E* Master Curves. As shown below, the typical Hot Mix Asphalt pavement weakens dramatically as pavement temperatures increase, providing only 5 to 10 percent the strength of the NaturalPAVE XL Resin Pavement when tested at 130OF temperature.

Figure 11

Figure 2







Dynamic Modulus for the NaturalPAVE Mixture at various Curing Periods under Fast Loading

Dynamic Modulus for the NaturalPAVE Mixture at various Curing Periods under Slow Loading

The Director of the Western Regional Superpave Center, Dr. Sebaaly, states in his report:Figures 11 and 12 show the E* (Dynamic Modulus) property of the NaturalPAVE mix under fast (i.e. 10

Hz) and slow (i.e. 1 Hz) loading conditions, respectively. The data in Figures 11 and 12 clearly show that the NaturalPAVE mix gains significant stiffness during the early part of the pavement life while it shows low risk for severe long term aging. The combination of the high magnitude of the E* (Dynamic Modulus) at the three curing stages and the moderate impact of temperature and frequency of loading makes the NaturalPAVE mixture a good candidate for a surface layer under a wide range of temperature, loading speed, and loading magnitude. The data shown in Figures 11 and 12 indicate that the NaturalPAVE mixture is expected to perform well under normal traffic loading (i.e. 10 Hz) and under the extreme conditions of high temperature and slow loading (i.e. 1 Hz).

11

Figure 12. Dynamic Modulus for the NaturalPAVE Mixture at various Curing Periods under Fast Loading.

Figure 13. Dynamic Modulus for the NaturalPAVE Mixture at various Curing Periods under Slow Loading.

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

10

Hz, k

si

Curing Time, hrs

70°F 100°F

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

1 H

z, k

si

Curing Time, hrs

70°F 100°F

11



100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

10

Hz, k

si

Curing Time, hrs

70°F 100°F

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

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ulus

|E*

| at

1 H

z, k

si

Curing Time, hrs

70°F 100°F

11



100

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10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

10

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si

Curing Time, hrs

70°F 100°F

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

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ulus

|E*

| at

1 H

z, k

si

Curing Time, hrs

70°F 100°F

11



100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

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ulus

|E*

| at

10

Hz, k

si

Curing Time, hrs

70°F 100°F

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

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Mod

ulus

|E*

| at

1 H

z, k

si

Curing Time, hrs

70°F 100°F

11



100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

10

Hz, k

si

Curing Time, hrs

70°F 100°F

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

1 H

z, k

si

Curing Time, hrs

70°F 100°F

11



100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

Mod

ulus

|E*

| at

10

Hz, k

si

Curing Time, hrs

70°F 100°F

100

1000

10000

0 72 144 216 288 360 432 504 576 648 720 792

Dyna

mic

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ulus

|E*

| at

1 H

z, k

si

Curing Time, hrs

70°F 100°F

Figure 12

Figure 13








Dynamic Modulus Setup

6


Dynamic Modulus



mix.

1

10

100

1,000

10,000

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz


Time

Strain

Time

time shift = φ

= 0sin(ωt)

0

0

= 0sin(ωt-φ)

0

0*E

Stress

6


Dynamic Modulus



mix.

1

10

100

1,000

10,000

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz


Time

Strain

Time

time shift = φ

= 0sin(ωt)

0

0

= 0sin(ωt-φ)

0

0*E

Stress

6


Dynamic Modulus



mix.

1

10

100

1,000

10,000

1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 1.E+00 1.E+01 1.E+02 1.E+03 1.E+04 1.E+05

Dyna

mic

Mod

ulus

|E*

|at 7

0F,

ksi

Frequency, Hz


Time

Strain

Time

time shift = φ

= 0sin(ωt)

0

0

= 0sin(ωt-φ)

0

0*E

Stress

Hot Mix Asphalt (HMA) specimen in Testing Aparatus







Dynamic Modulus Setup

NaturalPAVE XL Resin Pavement specimen in Testing Aparatus

The engineering evaluation of the NaturalPAVE XL Resin Pavement material was conducted under the direction of Peter Sebaaly, Ph.D., P.E., Director of the Western Regional Superpave Center, one of five centers established by the Federal Highway Administration (FHWA) to support the implementation of the Superpave Technology for hot mix asphalt materials. Dr. Sebaaly is also the Director of the Nevada Technology Transfer Center (funded by FHWA and Nevada DOT), and Professor of Civil Engineering in the Civil and Environmental Engineering Department at University of Nevada Reno where the Pavement/Materials Program and materials testing laboratory are located.






This laboratory evaluation under the direction of Dr. Sebaaly included Dynamic Modulus (E*) testing, the state of the art test method for evaluating Hot Mix Asphalt (HMA) materials, which are classified as flexible pavements, and providing input for AASHTO MEPDG pavement designs. Cold-mixed NaturalPAVE XL Resin Pavement materials also exhibit flexible behavior and Dynamic Modulus values similar to or higher than HMA materials. Consequently, the Dynamic Modulus test method is equally appropriate for evaluation of NaturalPAVE XL Resin Pavement materials and for pavement design purposes. The Dynamic Modulus test method is particularly adapted for evaluating HMA pavement materials because they exhibit dramatic changes in behavior under various combinations of traffic loads, speed, and environmental conditions, most notably changes in temperature. HMA materials are therefore described as viscoelastic in behavior. As evidenced in Figure 6 on Page 2, Typical Dynamic Modulus Data for Hot Mix Asphalt (HMA) Mixture, and in Figure 2 on Page 4, Typical E* Master Curve for a HMA Mix, a HMA pavement mixture can vary in Dynamic Modulus from under 10,000 psi (10 ksi) under slow loading in warmer weather to 2 million psi (2,000 ksi) when pavement temperatures cool to just above or slightly below freezing. Cold-mixed NaturalPAVE XL Resin Pavement materials have the advantage of gaining strength with additional curing time, most similar in this regard to concrete mixtures, which while classified as rigid pavement materials, also continue to gain strength with time. After just three days curing time, the Dynamic Modulus of the NaturalPAVE XL Resin Pavement in the worst case testing conditions, slow loading at 130OF pavement temperature, was at 200,000 psi (200 ksi), “...a very stable mix at the early stage of the pavement life...,” reports Dr. Sebaaly, and over 20 times the strength of typical HMA tested in these same conditions. After 30 days curing, the Dynamic Modulus values for the NaturalPAVE XL Resin Pavement vary from 300,000 psi (300 ksi), in worst case testing condition, up to above 2.7 million (2,700 ksi) in the testing conducted at cooler temperatures. By the point the Dynamic Modulus testing temperature is raised to 70OF and with just three days curing time, the NaturalPAVE XL Resin Pavement mix is already several times stronger than the HMA and approximately eight times stronger at 30 days. While the typical HMA material varies in its Dynamic Modulus by a factor of over 200 times under changing loading

rates and temperature changes from below freezing to 130OF, the NaturalPAVE material is far more consistent in strength retention with less than 7% of the variation in Dynamic Modulus exhibited by HMA. Dr. Sebaaly’s conclusion: “This indicates that the NaturalPAVE mixture behaves as viscoelastic but it is not as much influenced by variations in temperature and loading frequency as the typical HMA mixture.” While tested under fast and slow loading, the NaturalPAVE mix “... shows minimal potential for severe long term aging.” Dr. Sebaaly summarizes the report “The combination of the high magnitude of the E* (Dynamic Modulus) property at the three curing stages and the moderate impact of temperature and frequency of loading makes the NaturalPAVE mixture a good candidate for a surface layer under a wide range of temperature, loading speed, and loading magnitude. The data shown in Figures 11 and 12 indicate that the NaturalPAVE mixture is expected to perform well under normal traffic loading (10 Hz) and under the extreme conditions of high temperature and slow loading (1 Hz).”

The cold temperature (below freezing) behavior of NaturalPAVE XL Resin Pavement materials has also been evaluated in this same laboratory under the direction of Dr. Sebaaly in a previous laboratory study using the Thermal Stress Restrained Specimen Test, or TSRST procedure. The TSRST procedure is used to evaluate the low temperature performance of Hot Mix Asphalt (HMA) binder products. Asphalt binder products are formulated for service through a range of temperature conditions typical for the area where they are being used and their behavior is classified according to the Superpave Performance Grading (PG) System developed as part of the Strategic Highway Research Program (SHRP) funded by the Federal Highway Administration (FHWA). For perspective, HMA materials specified for cold climate applications, such as in the Upper Midwest and New England States, are specified for cold temperature performance as low as -28OC (PG 64-28) and -34OC temperatures (PG 64-34), with the -28OC and -34OC representing the cold weather component of the PG grading system. The NaturalPAVE XL Resin Pavement mixtures averaged -36.3OC performance in the TSRST evaluation, exceeding the low temperature performance requirements for the PG grade with the cold temperature specification of -34OC (-29OF).

Evaluation of NaturalPAVE XL Resin Pavement in Pavements/Materials Laboratory

comparison of typical dynamic modulus for hot mix asphalt ...sspco.com/docs/npv/2182.pdf · ......

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