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
– Task 2
– Task 3
– Task 4
– Task 5
– Task 6
– Task 7
Information Gathering
Selection of Pavement Test Sections
Status Meeting
Lab and Field Evaluation of MnROAD
Field Evaluation
Economic Evaluation
Final Report
Proposed Project Timeline
2010
2011
2nd Quarter 3rd Quarter 4th Quarter 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter
A M J J A S O N D J F M A M J J A S O N D
Task 1
Task 2
Task 3
Task 4
Task 5
QPR
2012
2013
2014
1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 1st Quarter 2nd Quarter 3rd Quarter 4th Quarter 1st 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 M
Task 5
Task 6
Task 7
QPR
indicates active work on a Task
indicates 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 nonload related distress?
Durability Parameter
Concept
Non-Cracking
Critical Range
Cracking
0
2
4
Year
6
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
DSR Mastercurve
DSR Function (Texas A&M)
DSR Monotonic (Wisconsin)
Ductility, 15°C
Force Ductility
BBR
DTT
PAV20
PAV40
PAV80
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
3.12E-06
4.44E-04
1.36E-03
Replicate 1
3.71E-06
3.87E-04
1.42E-03
Replicate 2
1.10E-05
4.02E-04
1.48E-03
Replicate 3
5.94E-06
4.11E-04
1.42E-03
Average
4.39E-06
2.95E-05
6.00E-05
Standard Deviation (1s)
73.8%
7.2%
4.2%
Coefficient of Variation (1s%)
80
6.19E-03
6.09E-03
6.40E-03
6.23E-03
1.58E-04
2.5%
Relationship between DSR Fatigue
Parameter and Ductility
Table 9: Comparison of Predicted and Measured Ductility
Measured
Standard DSR
Standard DSR
Mastercurve
Ductility
Pred. Ductility
G′/(′/G′)
G′/(′/G′)
(cm)
(cm)
MPa/s
MPa/s
0.5
3.38E-03
2.8
2.09E-02
1
1.18E-03
4.5
6.23E-03
1
1.75E-03
3.8
5.72E-03
1
2.18E-04
9.4
1.89E-03
4
2.55E-04
8.8
2.03E-03
4.25
3.40E-04
7.7
1.42E-03
5
3.90E-04
7.3
6.25E-04
6
1.20E-04
12.2
4.11E-04
10
1.45E-04
11.2
2.01E-04
Mastercurve
Pred. Ductility
(cm)
1.3
2.1
2.2
3.6
3.5
4.1
5.9
7.1
9.7
Relationship between DSR Fatigue
Parameter and Ductility
14
y = 0.79x + 4.63
R² = 0.57
Predicted Ductility, cm
12
10
y = 0.83x + 1.39
R² = 0.92
8
6
Mastercurve
4
Standard DSR
2
0
0
2
4
6
8
10
Measured Ductility, cm
12
14
Ductility at 15°C, 1 cm/min. (cm)
Mastercurve Procedure
12
10
y = 3.63E-02x -6.63E-01
R² = 8.57E-01
8
6
4
2
0
1.00E-03
1.00E-04
1.00E-02
1.00E-01
G'/('/G') @15°C, 0.005 rad/s (MPa/s)
West TX Sour
Gulf-Southeast
Western Canadian
Ductility at 15°C, 1 cm/min. (cm)
Standard DSR
12
10
y = 8.38E-03x -7.35E-01
R² = 6.66E-01
8
6
4
2
0
1.00E-05
1.00E-04
1.00E-03
1.00E-02
G'/('/G') @44.7°C, 10 rad/s (MPa/s)
West TX Sour
Gulf-Southeast
Western Canadian
Gulf-Southeast: BBR
-10.0
Temperature, °C
-15.0
-20.0
-25.0
Tc, S(60)
-30.0
Tc, m(60)
-35.0
-40.0
0
20
40
PAV Aging Time, Hrs
60
80
Effect of PAV Aging Time on DTc
Difference Between Tc,m(60) and Tc,S(60), °C
12.0
10.0
8.0
6.0
4.0
West Texas Sour
2.0
Gulf - Southeast
0.0
Western Canadian
-2.0
-4.0
-6.0
0
20
40
PAV Aging Time, Hrs
60
80
Ductility at 15°C, 1 cm/min. (cm)
Relationship between DTc and
Ductility
12
y = 7.77e -0.27x
R² = 0.74
10
8
6
4
2
0
-2.0
0.0
2.0
4.0
6.0
8.0
10.0
12.0
Difference Between Tc,S(60) and Tc,m(60), °C
West TX Sour
Gulf-Southeast
Western Canadian
Relationship between G′/(′/G′) and
DTc
G'/('/G') @15°C, 0.005 rad/s
(MPa/s)
1.00E-01
1.00E-02
1.00E-03
1.00E-04
1.00E-05
1.00E-06
1.00E-07
-6.0
-3.0
0.0
3.0
6.0
9.0
12.0
Difference Between Tc,m(60) and Tc,S(60), °C
West Texas Sour
Gulf - Southeast
Cracking Warning
Cracking Limit
Western Canadian
Relationship between G′/(′/G′) and
DTc
G'/('/G') @15°C, 0.005 rad/s
(MPa/s)
0
y = 0.0034x 3 - 0.0542x 2 + 0.4315x - 3.8249
R² = 0.9821
-1
-2
-3
-4
-5
-6
-7
-6.0
-3.0
0.0
3.0
6.0
9.0
12.0
Difference Between Tc,m(60) and Tc,S(60), °C
West Texas Sour
Gulf - Southeast
Cracking Warning
Cracking Limit
Western Canadian
Black Space Diagram: Western
Canadian Asphalt Binder
1.00E+09
1.00E+08
G*, Pa
1.00E+07
Original
1.00E+06
PAV-20
PAV-40
PAV-80
1.00E+05
5000 kPa
1.00E+04
1.00E+03
0
10
20
30
40
50
Phase Angle, degrees
60
70
80
90
Condition
Original
PAV-20
PAV-40
PAV-80
Approximate Phase Angle, degrees
(at G* = 5E+06 Pa)
61
49
45
38
Rheological Index – R
Glassy Modulus
Log G*
R
Crossover Frequency
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
log 2 * log G
R
where:
*
 
G
g
    
log1 

90 

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
Original
1.96a
1.44
PAV-20
1.95
1.89
PAV-40
2.06
2.12
PAV-80
2.67
2.51
a
Data is suspect due to poor mastercurve fit.
Western Canadian
1.37
2.16
2.43
2.97
Relationship between G′/(η′/G′)
and R (15°C, 0.005 rad/s)
DSR Parameter, MPa/s
1.00E-01
1.00E-02
WTX
GSE
1.00E-03
WC
1.00E-04
1.00
1.50
2.00
R(0.005 rad/s)
2.50
3.00
Field Core Data
Table 18: Comparison of Durability Parameters for Recovered Asphalt Binder Data
Roundup Top Roundup Bottom
Clayton
Conchas Lake
3.28E-04
6.80E-04
4.65E-04
6.66E-04
G’/(’/G’)1, MPa/s
0.5
2.9
2.2
3.5
DTc, °C
Predicted
Ductility2, cm
7.8
5.7
6.7
5.7
1
2
Determined at 15°C and 0.005 rad/s.
Ductility predicted using G’/(’/G’) and equation in Figure 3.
Relationship between G′/(′/G′) and
ΔTc (with Field Cores)
G'/('/G') @15°C, 0.005 rad/s
(MPa/s)
1.00E-01
1.00E-02
1.00E-03
1.00E-04
1.00E-05
1.00E-06
1.00E-07
-6.0
-3.0
0.0
3.0
6.0
9.0
12.0
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
3000
CMOD Displacement
2500
Delta 25 DisplacementAvg
Load, kN
2000
1500
1000
500
0
0
0.5
1
1.5
2
2.5
3
CMOD or Delta 25 Displacement, mm
3.5
4
4.5
Load
DC(t) Fracture Energy
Gf 
AREA
B * (W  a)
AREA
Crack Mouth Opening Displacement (CMOD)
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 polymermodified asphalt mixtures more broadly than
the indirect tensile strength test
Thanks!