Dynamic Modulus Testing Dynamic Modulus Testing of Iowa Asphalt ...

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Dynamic Modulus Testing Dynamic Modulus Testing of Iowa Asphalt ...

Dynamic Modulus Testing

of Iowa Asphalt Mixtures

Presented by

Xinjun Li

R. Christopher Williams

March 5, 2008

D t t f Ci il C t ti d E i t l E i i

Department of Civil, Construction and Environmental Engineering

Iowa State University


Introduction

‣ Superpave p mix design procedure

- Product of SHRP

‣ Different design levels based on traffic levels

- Volumetric mix design ( 10 7 ESALs)

2


Introduction (Cont’d)

‣ Superpave volumetric mix design

- No mechanical test t to check performance

- Marshall method includes mechanical test

‣ In the past years, comprehensive research

efforts to develop

- Simple performance test (SPT)

- To characterize material for the Mechanistic –

Empirical pavement design guide (AASHTO 2002)

‣ Recent research efforts (NCHRP 9-19, 1-37A)

- Complex dynamic modulus is a strong candidate for both pavement

design and SPT

- Recommended as a design parameter for rutting and fatigue cracking

- Not a good indicator for thermal cracking

3


Complex Dynamic Modulus

‣ Not a new concept

- Papazian, 1962

‣ Different research projects over decades

- Various combinations of frequencies and

temperatures

- Compression, tension-compression, tension

- Laboratory compacted and field cored specimens

‣ Most comprehensive in the past few years

- Professor Witzack and his research team (Arizona State Univ.)

- Compression

- Uniaxial loading and triaxial loading test

4


Background of Dynamic Modulus

(based on linear viscoelasticity concepts)

‣ Controlled sinusoidal load applied to cylindrical specimen

‣ Deformation measured at multiple locations on the sample

‣ Two fundamental parameters determined

- Dynamic modulus, lE*l

- Phase angle, δ

‣ Time-temperature superposition principle is assumed valid

‣ Master curve can be constructed using the factors from the

dynamic modulus tests – explains the behavior of mixtures

over a range of temperatures and rate of loading (fast vs.

slow)

5


Background of E* (cont’d)

‣ Determination of dynamic modulus

σ = σ

0 +

σ

1

cos( 2*

pi

*

f

*

t

+

φ1)

δ stress=σ σ o sin(ωt)

)

σ o

ε o

time

ε = ε

0

+ + ε1t

+ ε

2

cos( 2 * pi * f * t + φ2

)

E

*

=

φ = φ 2

−φ 1

strain=ε ε o sin(ωt-δ) 1

σ

ε

2

1

0.1 Hz @ 24.3°C

Force, kN

2.5

2.0

1.5

1.0

0.5

0.0

100.2 105.2 110.2 115.2 120.2 125.2 130.2 135.2 140.2 145.2 150.2 155.2

Time, sec

0.145

0.140

0135 0.135

0.130

0.125

0.120

0.115

0.110

0.105

0.100

mm

Extensometer Displacement,

σ, ε: stress and strain respectively,

t, f: time and frequency respectively,

σ 0 ,σ 1 ,ε 0 ,ε 1 ,ε 2 ,Φ 1 , Φ 2 : regression constants

ε 1 : slope of the drift curve of the displacement

|E*|, Φ: dynamic modulus and phase angle

6


Background of E* (cont’d)

‣ Master curve and shift factors

(Williams-Landel-Ferry model)

log α

T

=

C

1

( T − T

S

) T: temperature

T s : reference temperature

C

2

+ T − T S C 1 ,C 2 : constants

‣ Pellinen model

log

E

*

=

δ +

1

+

e

α

β −γ

log(

f r

)

δ: minimum modulus value

F r : reduced frequency

α: span of modulus values

β, γ: shape parameters

7


Objectives

‣ Established test protocol through shake

down evaluation

- The effect of temperature

- The effect of frequency

- The effect of strain level

- Damage assessment

‣ Performed dynamic modulus testing on

typical Iowa mixtures

- 21 Iowa asphalt mixtures

- Construct master curves for the MEPDG

8


Sample Preparation

‣ Sample preparation under comprehensive

investigation (NCHRP 9-29)

‣ Typical gyratory sample not homogenous

- Density gradation

- Across diameter (surface vs. interior)

- Top and bottom vs. interior

‣ Coring procedure recommended

- Prepare tall 6 ’’ gyratory specimen

- Obtain 4’’ by 6 ’’ tall specimen

9


Sample Preparation (Cont’d)

‣ Coring procedure

- Difficult to perform

‣ Possible solution

- Using slender 4 ’’ mold

10


Test Setup

Dynamic modulus test

(NCHRP Report 547)

11


Shake Down Test

‣ Five temperatures (from low to high)

- 4.4, 15, 21, 26 and 37°C

‣ Eleven frequencies (from high to low)

- 25, 15, 10, 7, 5, 2, 1, 0.7, 0.5, 0.3, and 0.1Hz

‣ Five replicates

‣ Two strain levels

- 80 and 120 micro-strains

‣ One mixture

- Jewell

12


Shake Down Test (cont’d)

‣ Using various frequency combinations to

check possible damage during testing

ti

Samples 25 15 10 7 5 2 1 0.7 0.5 0.3 0.1

5 X X X X X X X X X X X

5 X X X X X X X X

5 X X X X X

5 X X X

‣ Conditioned in the temperature chamber

‣ Capture the last seven cycles

13


‣ Replicates

Shake Down Test Results

- Consistent, no significant difference (t – test)

‣ Damage assessment

- No significant damage found

20

18

16

First 5 Hz

Second 5Hz

14

12

80-1-0.1hz

80-2-0.1hz

80-3-0.1hz

80-4-0.1hz

14

10

12

8

10

8

6

6

4

4

2

2

0

1 2 3 4 5

0

1 2 3 4 5

Five Replicates

Damage assessment

14


Shake Down Test Results (cont’d)

‣ Strain level effect

- No significant difference (t – test)

‣ Temperature and frequency effect

14

12

10

8

6

80 120

E* (GPa)

25

20

15

10

+4°C

15°C

21°C

26°C

37°C

4

2

5

0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

0

0 5 10 15 20 25 30

Two strain levels: 80 and 120με

Frequency (Hz)

15


Shake Down Test Results (Cont’d)

‣ Master curves

1.0.E+08

1.0.E+08

1.0.E+07

1.0.E+07

|E*|, KP Pa

1.0.E+06

4 15

21 26

37 Fit

Pa

|E*|, K

1.0.E+06

4 21

37 Fit

1.0.E+05

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

1.0.E+05

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

Frequency, Hz

Frequency, Hz

Five temperatures

Three temperatures

t

16


Five vs. Three Temperatures

1.0.E+08

10E+07 1.0.E+07

|E*|, KPa

1.0.E+08

4 15

21 26

1.0.E+06

4 21

1.0.E+07

37 Fit

37 Fit

|E*|, KPa

10E+06 1.0.E+06

4 21

37 Fit

1.0.E+05

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

Frequency, Hz

1.E+03 1.E+05 1.E+07

1.0.E+05

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

Frequency, Hz

Frequency, Hz

17


Shift Factors

3

3

2

2

r

Shift Factor

1

0

-1

0 10 20 30 40

Shift Factor

1

0

-1

0 10 20 30 40

-2

y = -0.1446x + 3.0995

R 2 = 0.9976

-2

y = -0.1414x + 3.05

R 2 = 0.9991

-3

-3

Temperature (°C)

Temperature (°C)

Five temperatures

Three temperatures

18


Dynamic Modulus for Iowa Mixtures

‣ Selected temperatures

- 4.4, 21 and 37°C

‣ Selected frequencies

- 25, 15, 10, 5, 2, 1, 0.5, 0.3 and 0.1

‣ 21 projects based on traffic level and binder PG

- 1M, 3M, 10M, 30M and 100M ESALs

- PG58-28, 64-28, 64-22, 70-22 and 76-28

19


Test Results for Iowa Mixtures

1.0.E+08

10E+07 1.0.E+07

|E*|, KPa

1.0.E+06

1.0.E+05

Jewell

I80S

I235S

Dedham

NW

330B

218T

HW4

330S

235B

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

Frequency, Hz

20


Summary

Dynamic modulus shake down test

- Five temperatures t and eleven frequencies

- Two different strain levels

‣ No statistical difference found

- strain level, replicates

‣ No accumulated damage found

‣ Master curve build

‣ E* test protocol built for Iowa mixtures

- Three temperatures & Nine frequencies

‣ Mix performance appears to coincide with

volumetric design levels

21


Iowa DOT

Acknowledgements

– John Hinrichsen

– YoonJoo Kim

– Kevin Jones

‣ Mike Heitzman

‣ Members of APAI

22


Thank you!

Questions?

23

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