rahbar-rastegar-comparison of aging methods for ......short title; author(s), date project overview...

Short title; Author(s), Date

Comparison of Different Laboratory Aging Methods for Performance Evaluations

Reyhaneh Rahbar-RastegarJo Sias Daniel and Eshan V. Dave

NESMEA 2017 Annual MeetingOctober 18, 2017

Hartford, CT


Aging

§ Hot mix asphalt pavements undergo aging during mixing and compaction, and over the service life.

• Short term aging (mixing and compaction)• Long term aging (pavement service life)

§ Aging effects:

§ Increase of stiffness§ Decrease of relaxation More cracking susceptibility§ Increase of brittleness

2


Project Overview

§ NHDOT Project 26962O § 10 plant mixed, lab compacted mixtures

§ PG 58-28, PG 52-34§ 12.5 and 19 mm NMAS§ 20 and 30% RAP, RAP/RAS

§ Binder testing § Mixture testing

§ To investigate how mixtures linear viscoelastic (LVE), fracture, and

fatigue properties change with different aging levels.

§ To investigate impact of different long term lab conditioning

protocols.

3

Objectives


Laboratory AgingüShort-term aging condition üLong-term aging condition

• 5 days, 85 ℃ for compacted samples (AASHTO R30)

• 5 days, 95 ℃, loose mix (NCHRP 9-54 project)

• 12 days, 95 ℃, loose mix (NCHRP 9-54 project)

• 24-hour, 135 ℃, loose mix (Asphalt Institute)

4


Mixture Testing and Parameters§ Complex Modulus Testing (AASHTO TP-79)

§ ǀE*ǀ and d master curve

§ Black Space Diagram

§ Higher E* and lower dè more potential to cracking

§ Mixture Glover-Rowe !∗($%& '))

*+,'

(Mensching, et al., 2016)

at 15 ℃ and 0.005 rad/s

Higher mixture G-R è more cracking susceptibility

5

100

1000

10000

100000

5 15 25 35 45

Dyn

amic

Mod

ulus

(M

Pa)

Phase Angle (Degrees)


LVE Characteristics

§ Higher dynamic modulus and lower phase angle for LTOA mixtures.

§ Change of phase angle master curve shape; horizontal and vertical shift in peak phase angle

6


LVE Characteristics

§ Higher stiffness for LTOA mixtures (difference varies between 1 to 6 times).

§ Lower relaxation at high and intermediate freq. and higher relaxation at low freq. for LTOA mixes.

7


Black Space Diagram

§ For same level of thermal stress, relaxation capabilities of asphalt mixtures would diminish with increasing aging levels.

8


Mixture G-R Parameter

§ Increase of the ratio in higher aging levels.§ 12 days (95 ℃) and 24 hr. (135 ℃) have similar

values.

9


Mixture Testing and Parameters§ Uniaxial Fatigue Testing

• Based on Simplified Viscoelastic Continuum Damage approach (AASHTO TP 107)

• Damage Characteristics Curve (C – S)

• Fatigue Failure Criterion (GR – Nf)

• Nf @ GR=100

§ GR : The rate of change of the averaged released pseudo strain energy (per cycle) throughout the entire history of the test.

10

1

10

100

1000

1000 10000 100000 1000000

GR

Number of cycles (Nf)

0

0.2

0.4

0.6

0.8

1

0 50000 100000 150000 200000 250000

C (

Pseu

do S

tiffn

ess)

S (Damage)


Fatigue Properties (C-S)

11

0

0.2

0.4

0.6

0.8

1

0 50000 100000 150000 200000 250000

C*(Psuedo*Stiffness)

S*(Damage)

20%*RAP*Mixtures

STOA,*52E3424*hr.*135C,*52E3412*days,*95C,*52E345*days,*95C,*52E34STOA,*58E2824*hr.*135C,*58E2812*days,*95C,*58E28

0

0.2

0.4

0.6

0.8

1

0 50000 100000 150000 200000 250000

C*(Psuedo*Stiffness)

S*(Damage)

20%*RAP/RAS*Mixtures

STOA,*52F3424*hr.*135C,*52F3412*days,*95C,*52F345*days,*95C,*52F34STOA,*58F2824*hr.*135C,*58F2812*days,*95C,*58F285*days,*95C,*58F28

§ Similar integrity for STOA and 5 days LTOA, but high levels of aging make significant difference.

§ Similar C-S curves for PG 58-28 and PG 52-34 mixtures.


Mixture Testing and Parameters§ Disk-Shaped Compact Tension (DCT) Test (ASTM D7313-13)§ Semi-Circular Bend (SCB) Test (AASHTO TP 124)

• Fracture Energy (Gf = work / fracture surface area)

• Flexibility Index (FI = Gf / Slope at inflection point)

• Fracture Strain Tolerance (FST = Gf / Fracture strength)

12

0

0.5

1

1.5

2

2.5

3

3.5

4

0 2 4 6 8

Load

(kN

)

Displacement (mm)

Post Peak Slope

Area under the curve = Work

PeakLoad(usedtocalculatefracturestrength,St)


Fracture Properties, FST=(Gf/Sf)

§ Higher FST for 5 days aging than 12 days.§ 24 hr. have higher FST than 12 days for RAP/RAS

mixtures.

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Conclusion§ All levels of long term aging have made a significant

increase on LVE properties (ǀE*ǀ and δ)

§ 24 hour (135 ℃) and 12 days (95 ℃) aging levels create similar effects on LVE properties, but not on fatigue and fracture properties.

§ Cracking resistance (FST) decrease as the aging level changes from 5 days to 12 days, but there is not an evident trend between the fracture properties of 24 hour and 12 days.

§ This study supports 12 days at 95 ℃ aging protocol on basis of fracture test results.

14


Future Work

§ Expand the data base, additional mixtures from

different locations of country.

§ Testing and analysis of cores that have been aged in

the field.

§ Extend this research to develop an aging prediction

model.

§ Develop new thresholds for available cracking

parameters with the effect of aging.

15


Acknowledgement

§ New Hampshire Department of Transportation

§ Pike Industries, Inc.

§ UNH Asphalt Research Group

16


Thank you!any questions?

Reyhaneh RahbarEmail: [email protected]

Tel: 765-494-7289

17


Mixture Testing and Parameters

§Shape parameters

• E* master curve• Sigmoidal model: log 𝐸∗ = 𝛿 + 5

6789:;(?)

• (- 𝛽/ 𝛾) vs. (𝛾)

• d master curve

• Lorentzian model: 𝛿 = B.D)

(E%F(G)HI))7D)

• (c) vs. (a)

18

0

10

20

30

40

50

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

Phase

Angl

e (d

egre

es)

Reduced Frequency (Hz)

STOA

LTOA

Related to c

∆a


Shape Parameters

19

§ The evolution of shape parameters with aging.§ More variation in 24 hr., 135∘C aged mixtures.


Fracture Properties, FI (SCB)

20

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