Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in Hot-Mix Asphalt Pavement

Pooled Fund Study TPF5-153

MnROAD

27 May 2010

Research Team

• Asphalt Institute– Mike Anderson, PI– Phil Blankenship, Senior Research Engineer

• AMEC– Doug Hanson, Researcher

• Consultant– Gayle King, Researcher

Research Objectives

• Primary Objective– to develop and validate technology that can be

used by the Minnesota DOT (Mn/DOT) and other highway agencies to determine the proper timing of preventive maintenance in order to mitigate damage caused by asphalt aging.

• Help highway agencies to define a pavement preservation strategy which optimizes life-cycle cost while maintaining safety and serviceability for the driving public, with primary emphasis on countering the deleterious effects of asphalt aging

Expected Deliverables

• Expected deliverables:– Identification of an asphalt binder or mixture parameter

related to durability as a result of environmental aging that can be determined from testing of pavement cores.

– Specification limits (Warning and Action limits) for the durability parameter that indicate the need for preventive maintenance.

– Guidelines for monitoring the durability parameter during the life of an asphalt pavement.

– Economic evaluation of the cost effectiveness of applying surface treatments at various times in the life of an asphalt pavement.

– Final Report describing the results of the research.

Research Tasks

• Tasks– Task 1 Information Gathering– Task 2 Selection of Pavement Test Sections– Task 3 Status Meeting– Task 4 Lab and Field Evaluation of MnROAD– Task 5 Field Evaluation– Task 6 Economic Evaluation– Task 7 Final Report

Proposed Project Timeline

A M J J A S O N D J F M A M J J A S O N DTask 1Task 2Task 3Task 4Task 5QPR

2010 20112nd Quarter 3rd Quarter 4th Quarter 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter

J F M A M J J A S O N D J F M A M J J A S O N D J F MTask 5Task 6Task 7QPR

20141st Quarter

2012 20131st Quarter 2nd Quarter 3rd Quarter 4th Quarter 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter

indicates active work on a Taskindicates active work on Quarterly Progress Report (QPR)

Task 1

• Information Review– Review mechanisms for environmental aging– Review binder properties that are affected by aging– Review test methods used to evaluate binder properties– Review modes of pavement distress caused by aging and

surface treatments used to mitigate these distresses.– Review pavement preservation techniques

• US and international• Determine current best-practice with regard to the timing of

surface treatments• Assess new technologies that could deserve accelerated

deployment

Task 2

• Selection of Pavement Test Sections– MnROAD

• Determine which sections have received surface treatments

• Determine what tests have already been performed

• Determine what retained materials are available for testing

– Other pavement test sections

Task 3

• Status Meeting– After completion of Tasks 1 and 2– Draft interim report

• Findings to date

Task 4

• Laboratory and Field Evaluation of MnROAD and Other Test Sections– Objective

• identify test methods that correctly rank distress• determine critical binder or mixture failure limits

that might be used as objective triggers for the various preservation strategies

Task 4

• Laboratory and Field Evaluation of MnROAD and Other Test Sections

• Critical fracture parameters monitored throughout the life of the pavement

– Appropriate remedial action can be taken as the critical limit is approached

• Simple tests to be used for field monitoring purposes

– physical properties from simple tests correlated to crack predictions from DC(t) or other more sophisticated fracture tests.

AAPTP 06-01 Question

• As the Airport Manager…– What test do I run or what calculation can I do

that will tell me when the pavement is expected to begin showing significant non-load related distress?

Concept

0 2 4 6

Year

Dur

abili

ty P

aram

eter

Critical Range

Cracking

Non-Cracking

Concept for Non-Load Related Distress

• Options– Use conventional construction data (e.g.

binder properties, density, etc.) with climatic data together in an aging/cracking model to project time to remediation

– Run mix test on cores at construction to get cracking property and fit data within aging/cracking model to project time to remediation

Concept for Non-Load Related Distress

• Options– Run binder test on sample recovered from

cores at construction to get cracking property and fit data within aging/cracking model to project time to remediation

– Run binder and/or mix test at construction to get cracking property and continue to pull cores from pavement at periodic intervals to check progression of cracking property

Task 4

• Selected Test Sections– Inspected on a yearly basis for age-related

damage• MnROAD performance measures will be

supplemented with careful monitoring to classify the types and origins of visible cracks

– Cores• 10• Between wheel path, closely spaced longitudinally

Task 4 Cores

Gmm

Recovered Binder Testing

Mixture BBR Testing

Mixture DC(t) Testing

Extra

Task 4 Cores:Binder, Mix BBR Testing

Layer A

Layer B

Layer C

Layer D

50 mm

Task 4 Cores: Binder Testing

• Layer A– Extraction/Recovery

• Centrifuge extraction using toluene/ethanol• Recovery using Rotavapor and AASHTO T319

– Lower temperature, higher vacuum

– 2 Cores (150-mm diameter x 12.5-mm thickness)

• ~50 grams asphalt– assuming Gmb=2.300 and asphalt content = 5.0%

Task 4 Cores: Binder Testing

• Layer A– DSR Frequency Sweep

• Three temperatures (5, 15, 25°C) using 8-mm plates

– Possible different temperatures?

• Rheological mastercurves for modulus (G*) and phase angle (δ)

– DSR at 45°C, 10 rad/s • G′/(η′/G′)

Task 4 Cores: Binder Testing

• Layer A– BBR

• 2-3 temperatures• Tc determined to the nearest 0.1°C for S(60) and

m(60)• Difference in Tc

Task 4 Cores: Binder Testing

• Layer A– DENT

• Double-edge notched tension• Conducted at intermediate temperatures using

modified ductility molds• Proposed by Professor Simon Hesp• Intended to examine ductile failure and provide an

indication of the crack tip opening displacement and essential work of fracture

Task 4 Cores: Binder Testing

• Layer A– Linear Amplitude Sweep

• Conducted at intermediate temperatures using DSR

• Strain increases linearly until failure• Proposed by Dr. Hussain Bahia• Continuum damage approach to calculate fatigue

resistance

Task 4 Cores: Mixture Testing

• Layer A– Mixture BBR Testing

• Conducted at 2 temperatures using BBR– Low binder grade temperature +10°C– Low binder grade temperature +22°C

• Work by Dr. Mihai Marasteanu

Task 4 Cores: Mixture Testing

• Top 50-mm of Core– Mixture DC(t) Testing

• Disk-shaped compact tension test• Conducted at low binder grade temperature +10°C• Work by Dr. Bill Buttlar• Fracture energy

– May be related to top-down cracking

Task 5

• Field Evaluation– Evaluation of test sections in July each year– Cores obtained

• Tested using best procedure identified in Task 4• Time dependence of durability parameter

Task 6

• Economic Evaluation– Time dependence of durability parameter– Recommended practice to evaluate durability– Recommended limits for preventative and

corrective action

Task 7

• Final Report– Report– Executive Summary (1-2 pages)– Technical Brief (4 pages)

• describe the durability parameter• explain testing procedures needed to determine the

durability parameter• provide suggested specification limits indicating when

pavement remediation is impending• provide suggested monitoring guidelines for asphalt

pavements to effectively capture the durability reduction as a function of time

Task 7

• Final Report– Workshop

• Understand what the durability parameter is, how it is obtained, what the numbers mean, and how to know when to take action

• 4-8 hours• Conducted as a webinar or on-demand video

presentations?

Recent Research Findings

• AAPTP 06-01: Techniques for Prevention and Remediation of Non-Load Related Distresses on HMA Airport Pavements (Phase II)– Asphalt Binder Testing

• establish correlations between fracture and rheological properties as asphalt binders age in a mix or in the PAV

Recent Research Findings:AAPTP 06-01

• Asphalt Binders– West Texas Sour (PG 64-16)– Gulf-Southeast (PG 64-22)– Western Canadian (PG 64-25)

Table 1: Asphalt Binder Testing Matrix Unaged PAV20 PAV40 PAV80 DSR Mastercurve DSR Function (Texas A&M) DSR Monotonic (Wisconsin) Ductility, 15°C Force Ductility BBR DTT

Relationship between Ductility and DSR Parameter

(Glover et.al., 2005)

DSR Fatigue Parameter (derived from Mastercurve)

Table 3: Gulf-Southeast – G′/(′/G′) at 15°C, 0.005 rad/s (MPa/s) Aging Time, hrs. 0 20 40 80 Replicate 1 Replicate 2 Replicate 3

3.12E-06 3.71E-06 1.10E-05

4.44E-04 3.87E-04 4.02E-04

1.36E-03 1.42E-03 1.48E-03

6.19E-03 6.09E-03 6.40E-03

Average 5.94E-06 4.11E-04 1.42E-03 6.23E-03

Standard Deviation (1s) 4.39E-06 2.95E-05 6.00E-05 1.58E-04

Coefficient of Variation (1s%) 73.8% 7.2% 4.2% 2.5%

Relationship between DSR Fatigue Parameter and Ductility

Table 9: Comparison of Predicted and Measured Ductility Measured Ductility

(cm)

Standard DSR G′/(′/G′) MPa/s

Standard DSR Pred. Ductility

(cm)

Mastercurve G′/(′/G′) MPa/s

Mastercurve Pred. Ductility

(cm) 0.5 3.38E-03 2.8 2.09E-02 1.3 1 1.18E-03 4.5 6.23E-03 2.1 1 1.75E-03 3.8 5.72E-03 2.2 1 2.18E-04 9.4 1.89E-03 3.6 4 2.55E-04 8.8 2.03E-03 3.5

4.25 3.40E-04 7.7 1.42E-03 4.1 5 3.90E-04 7.3 6.25E-04 5.9 6 1.20E-04 12.2 4.11E-04 7.1 10 1.45E-04 11.2 2.01E-04 9.7

Relationship between DSR Fatigue Parameter and Ductility

y = 0.83x + 1.39R² = 0.92

y = 0.79x + 4.63R² = 0.57

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12 14

Pred

icte

d D

ucti

lity,

cm

Measured Ductility, cm

Mastercurve

Standard DSR

Mastercurve Procedure

y = 3.63E-02x-6.63E-01

R² = 8.57E-01

0

2

4

6

8

10

12

1.00E-04 1.00E-03 1.00E-02 1.00E-01

Duc

tilit

y at

15°

C, 1

cm

/min

. (cm

)

G'/( '/G') @15°C, 0.005 rad/s (MPa/s)

West TX Sour Gulf-Southeast Western Canadian

Standard DSR

y = 8.38E-03x-7.35E-01

R² = 6.66E-01

0

2

4

6

8

10

12

1.00E-05 1.00E-04 1.00E-03 1.00E-02

Duc

tilit

y at

15°

C, 1

cm

/min

. (cm

)

G'/( '/G') @44.7°C, 10 rad/s (MPa/s)

West TX Sour Gulf-Southeast Western Canadian

Gulf-Southeast: BBR

-40.0

-35.0

-30.0

-25.0

-20.0

-15.0

-10.0

0 20 40 60 80

Tem

pera

ture

, °C

PAV Aging Time, Hrs

Tc, S(60)

Tc, m(60)

Effect of PAV Aging Time on Tc

-6.0

-4.0

-2.0

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 20 40 60 80

Diff

eren

ce B

etw

een

Tc,m

(60)

and

Tc,

S(60

), °C

PAV Aging Time, Hrs

West Texas Sour

Gulf - Southeast

Western Canadian

Relationship between Tc and Ductility

y = 7.77e-0.27x

R² = 0.74

0

2

4

6

8

10

12

-2.0 0.0 2.0 4.0 6.0 8.0 10.0 12.0

Duc

tilit

y at

15°

C, 1

cm

/min

. (cm

)

Difference Between Tc,S(60) and Tc,m(60), °C

West TX Sour Gulf-Southeast Western Canadian

Relationship between G′/(′/G′) and Tc

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

-6.0 -3.0 0.0 3.0 6.0 9.0 12.0

G'/

('/

G')

@15

°C, 0

.005

rad/

s(M

Pa/s

)

Difference Between Tc,m(60) and Tc,S(60), °C

West Texas Sour Gulf - Southeast Western Canadian

Cracking Warning Cracking Limit

Relationship between G′/(′/G′) and Tc

y = 0.0034x3 - 0.0542x2 + 0.4315x - 3.8249R² = 0.9821

-7

-6

-5

-4

-3

-2

-1

0

-6.0 -3.0 0.0 3.0 6.0 9.0 12.0

G'/

('/

G')

@15

°C, 0

.005

rad/

s(M

Pa/s

)

Difference Between Tc,m(60) and Tc,S(60), °C

West Texas Sour Gulf - Southeast Western Canadian

Cracking Warning Cracking Limit

Black Space Diagram: Western Canadian Asphalt Binder

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

0 10 20 30 40 50 60 70 80 90

G*,

Pa

Phase Angle, degrees

Original

PAV-20

PAV-40

PAV-80

5000 kPa

Condition Approximate Phase Angle, degrees (at G* = 5E+06 Pa)

Original 61 PAV-20 49 PAV-40 45 PAV-80 38

Rheological Index – R

Glassy Modulus

R

Crossover Frequency

Log

G*

Log Frequency

Rheological Index

• SHRP Report A-369– Rheological Index, R, is the difference

between the glassy modulus and the complex shear modulus at the crossover frequency (where tan δ = 1).

Rheological Index

• SHRP Report A-369– “…[R] is directly proportional to the width of

the relaxation spectrum and indicates rheologic type. R is not a measure of temperature, but reflects the change in modulus with frequency or leading time and therefore is a measure of the shear rate dependency of asphalt cement. R is asphalt specific.”

Calculating R

901log

log*2log*

GG

gR

where: G*(ω) = complex shear modulus at frequency ω (rad/s), Pa Gg = glassy modulus, Pa (assumed to be 1E+09 Pa) (ω) = phase angle at frequency ω (rad/s), degrees (valid between 10 and 70°)

Determination of R at Same Conditions as G′/(η′/G′)

Table 16: Determination of R (15°C, 0.005 rad/s) West Texas Sour Gulf Southeast Western Canadian Original 1.96a 1.44 1.37 PAV-20 1.95 1.89 2.16 PAV-40 2.06 2.12 2.43 PAV-80 2.67 2.51 2.97 a Data is suspect due to poor mastercurve fit.

Relationship between G′/(η′/G′) and R (15°C, 0.005 rad/s)

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00 1.50 2.00 2.50 3.00

DSR

Par

amet

er, M

Pa/s

R(0.005 rad/s)

WTX

GSE

WC

Field Core Data

Table 18: Comparison of Durability Parameters for Recovered Asphalt Binder Data Roundup Top Roundup Bottom Clayton Conchas Lake G’/(’/G’)1, MPa/s 3.28E-04 6.80E-04 4.65E-04 6.66E-04 Tc, °C 0.5 2.9 2.2 3.5 Predicted Ductility2, cm

7.8

5.7

6.7

5.7

1 Determined at 15°C and 0.005 rad/s. 2 Ductility predicted using G’/(’/G’) and equation in Figure 3.

Relationship between G′/(′/G′) and ΔTc

(with Field Cores)

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

-6.0 -3.0 0.0 3.0 6.0 9.0 12.0

G'/

('/

G')

@15

°C, 0

.005

rad/

s(M

Pa/s

)

Difference Between Tc,m(60) and Tc,S(60), °C

West Texas Sour Gulf - Southeast Western Canadian

Cracking Warning Cracking Limit Recovered

Witczak and Mirza:Global Aging Model (1995)

DC(t)

DC(t) Specimen (after testing)

DC(t) Data Output

0

500

1000

1500

2000

2500

3000

0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Lo

ad, k

N

CMOD or Delta 25 Displacement, mm

CMOD Displacement

Delta 25 Displacement-Avg

DC(t) Fracture Energy

Crack Mouth Opening Displacement (CMOD)

Lo

ad

AREA)(* aWB

AREAGf

DC(t) Results

DC(t)

• What is It?– Fracture energy test for asphalt mixtures

• modeled after a fracture toughness test for metals

• Developed by researchers at the University of Illinois to evaluate the cracking performance of field cores and laboratory-compacted HMA samples.

• What Type of Specimen is Tested?– Cylindrical specimen with a single-edge notch

– Usually 50-mm thick

– Can be lab-produced or field core

DC(t)

• How Does the Test Work?– Specimen loaded on its side– A gauge is placed at the notch and the

opening of the “crack mouth” is recorded as the specimen is loaded in tension.

– The fracture energy is calculated using specimen dimensions and the area under the load-displacement curve.

– Generally valid at temperatures of ~10° C (50° F) and lower.

DC(t)

• Why Use this Test?– Fracture test– Successfully used on several projects to

describe the cracking resistance of asphalt concrete.

– Believed to discriminate between polymer-modified asphalt mixtures more broadly than the indirect tensile strength test

Thanks!