Department of Civil and Environmental EngineeringUniversity of Illinois at Urbana-Champaign

Alex Apeagyei

Prof Bill Buttlar

Prof Barry Dempsey

Development of Antioxidant Treatments for Asphalt Binders and Mixtures

November 9, 2005

Outline of Presentation

IntroductionResearch Approach

Experimental Design

Analysis of Results

Summary and Conclusions

Recommendations

Introduction: – Purpose of Study

The goal was to develop Antioxidant (AOX)

treatments …

… to reduce oxidative aging in asphalt binders and mixtures

Problem Statement

The problem of asphalt aging still exists despite

the extensive use of antioxidants:

Issues:

Sacrificial AOX, get consumed with time

Extensive degradation after 2-6 years

Possible environmental concerns

Experimental Plan

Selection of AOXs:- Eight additives

Binder testing

RTFO, PAV Dynamic Shear Rheometer (DSR) Test Bending Beam Rheometer (BBR) Test

Mixture testing Tests performed on most promising AOX system Creep Compliance, Dynamic modulus, Tensile

strength, DC(T) Fracture Energy, Moisture damage

List of AOXs evaluated

1. Irganox 1010

2. Vitamin E (Irganox E201)

3. Irgafos P-EPQ

4. Dilaurylthiodipropionate (DLTDP)

5. Furfural

6. Acryloid B-48N

7. Carbon Black (Raven 790)

8. Hydrated Lime

Evaluation of Aging

Aging Index (AI) used for evaluating aging

AI of binders based on SUPERPAVE Parameters

G*/Sin at 64 ºC

G*Sin at 25 ºC

AI of mixtures based on Creep Compliance, E*, Tensile Strength, Fracture

Energy

unaged

RTFOaged

SinG

SinGAI

/*

/*

Evaluation of Binder Results

Comparison of binder AI after RTFO

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

Specimen

Ag

ing

Ind

ex

AOX-Modified

Control

Aging Index: G*Sin at 25 ºC after PAV

S13

S14

S16

1.0

3.0

5.0

7.0

Sample

Ag

ing

Ind

ex

S13 – DLTDP + Furfural + Catalyst

S14 – Vitamin E + Furfural + catalyst

S16 - Control

Effect of AOXs on G*Sin after PAV

S13

S16 S14

0.0

2.0

4.0

6.0

Sample

Sti

ffn

ess

at 2

5 C

(M

Pa)

Control

Effect of AOXs on Creep Stiffness after PAV

Control

S13

S16S14

0

40

80

120

160

Sample

Sti

ffn

ess

at -

12 C

(M

Pa)

Effect of AOXs on m-value at after PAV

Control

S13

S16S14

0.35

0.40

0.45

0.50

Sample

m-v

alu

e

Effects of AOX on long-term binder aging

0.0

2.0

4.0

6.0

8.0

10.0

25 ºC 64 ºC

Ag

ing

In

dex

Control AOX-Mod

Improvement 40%

Improvement 20%

Selection of most promising AOX

S13 contains DLTDP/Furfural + catalyst

S13 is most preferred AOX treatment

Sample S13 will be labeled AOX-Modified

Asphalt concrete mixtures limited to S13

Asphalt Mixture Fabrication

Materials:

Limestone aggregates (9.5 mm Nom. Max)

PG 64-22 binder (Control)

AOX-Modified PG 64-22 binder

Mixture Aging

Short-term oven aging (135 ºC for 2 hours, STOA-2h)

Long-term oven aging (135 ºC for 8 hours, LTOA-8h)

Mixture Tests Performed

1. Creep Compliance

2. Dynamic Modulus E*

3. Indirect Tensile Strength

4. DC(T) Fracture Test (Wagoner et al. 2004)

5. Moisture Susceptibility

Creep Compliance master curve (Tref = -20 C)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

1 100 10000 1000000

Reduced Time (sec)

Cre

ep C

om

plia

nce

(1/

GP

a)

Control-STOA-2h: m=0.47 Modified-STOA-2h: m=0.4021Modified-LTOA-8h: m=0.3813 Control-LTOA-8h: m=0.3597

Effect of aging on creep compliance

0.0

0.2

0.4

0.6

0.8

1.0

1 1000 1000000

Reduced Time (sec)

Ret

ain

ed

Cre

ep C

om

plia

nce

AOX-ModifiedControl

E* master curve (Tref = 20 ºC)

0

5000

10000

15000

20000

25000

0.001 0.1 10 1000 100000 1E+07

Reduced Frequency (Hz)

Dyn

am

ic M

od

ulu

s E

* (M

Pa)

Mod-LTOA-8hMod-STOA-2hContr_LTOA-8hContr-STOA-2h

Tref = 20 0C

Effect of aging on dynamic modulus E*

1.0

1.4

1.8

2.2

0.001 0.1 10 1000 100000 1E+07

Reduced Frequency (Hz)

Ag

ing

Ind

ex

AOX-ModifiedControl

DC(T) Fracture Testing

Test Setup

DC(T) Specimen

Effect of Aging on Fracture Energy

0.0

0.4

0.8

1.2

1.6

0 ºC -10 ºC

Ret

ain

ed F

ract

ure

En

erg

y

Control

AOX-Mod

Moisture Susceptibility

To investigate the moisture damage

potential of AOX-Modified Asphalt Mix

Tests performedAASHTO T283 [Tensile Strength Ratio, TSR]DC(T ) [Fracture Energy Ratio, FER]

Aggregates used: Limestone

Limestone Results Summary

0.0

0.4

0.8

1.2

1.6

TSR FER

Mo

istu

re D

amag

e ra

tio

Control

AOX-Mod

Limestone mixtures: Visual rating

74.0TSR 43.0TSR

Conclusion

The AOX treatments evaluated during this

study appear to cause significant reduction in

age-hardening of the PG 64-22 asphalt used

Recommendations

Evaluate AOXs using different asphalt sources

Full-scale production of the AOX-Modified

Construction of Full-scale pavement sections

Accelerated testing

Long-term performance evaluation

Acknowledgements

Research conducted at ATREL and was

supported by the Center of Excellence for

Airport Technology funded by the FAA

Special thanks to:

Prof Barry Dempsey – Director of Research

Prof Bill Buttlar – Advisor

End of Presentation

Thank You!