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S1SP ARA0127-1
Modified Asphalt Binders –Enhancing Pavement
Performance
Harold L. Von Quintus, P.E.
51st Annual Idaho Asphalt ConferenceOctober 27, 2011
Expanding the Realm of Possibility2
Focus● Overview the effect of modified
asphalt binders for enhancing pavement performance – extending the service life of new pavements and overlays.
Expanding the Realm of Possibility3
Effect of Binder on Performance
1. Thermal Cracking2. Fatigue Cracking3. Rutting
Most, if not all agencies in U.S. have adopted the P-G specifications & many have reported reduced distress; especially thermal cracking.
Expanding the Realm of Possibility
Effect of Binder on PerformanceImproved pavement performance
observations after implementing P-G binder specificationMinistry of Transportation, OntarioColoradoMichiganMissouriUtah
4
BUT, other changes made: Gyratory compactor, use of polymer modified asphalt, revised QA specifications,
pavement preservation, etc.
Expanding the Realm of Possibility
Michigan:Distress Index –systematic reduction over time.
5
Expanding the Realm of Possibility
Effect of BinderDifficult to quantify because multiple changes made or materials implemented within the same time period.Asphalt binders by themselves will not significantly improve performance – my opinion.
6
HISTORY: Many laboratory studies have shown PMA enhances fracture and
distortion resistant properties – BUT field quantification of benefit is limited.
S1SP ARA0127-7
Performance Comparisons:Neat versus Modified Binders
Quantification of the Effects of Polymer-Modified Asphalt to Enhancing HMA
Performance, Sponsored by the Affiliate Committee, Asphalt Institute.
Expanding the Realm of Possibility8
Distress Comparison for Companion Sections 1. Fatigue Cracking; Area &
longitudinal combined2. Rutting3. Thermal Cracking
Companion Sections – Two sections where the only difference is the asphalt
binder.
Expanding the Realm of Possibility9
PMA Versus Neat SectionsComparison of Actual Distresses
RuttingFatigue CrackingTransverse Cracking
M-E Analysis of Performance DistortionFracture
M-E Based Procedure normalizes any difference between companion sections.
Expanding the Realm of Possibility10
Rutting
Neat MixesVersus
PMA Mixes
Expanding the Realm of Possibility11
What is the time difference between different rut depths?
0
0.2
0.4
0.6
0.8
1
1.2
0 0.5 1
Rut Depths on PMA Sections, inches
Rut
Dep
ths
on C
onve
ntio
nal
Sect
ions
, inc
hes
Years for equal rutting?
Expanding the Realm of Possibility12
Distortion AnalysisVertical strain at specific depthsNeat sections individually calibrated & used to predict PMA rutting.
RNnDI =
HMA Surface
HMA Base
Granular Base
Subgrade
εV
εV
( )( ) ( )
( ) ( ) ( )( )( )( )
∑=
−
⎟⎟⎟⎟
⎠
⎞
⎜⎜⎜⎜
⎝
⎛
=n
i
ir
abeff
Cr
tC
VVT
NCx
RD
r
13
5213.00057.15896.2
4289.01
7 21037.5
ε
Expanding the Realm of Possibility13
Rutting – Neat Vs PMA
00.10.20.30.40.50.60.70.80.9
1
0 0.2 0.4 0.6 0.8 1
Predicted Rut Depth - Local Calibration, inches
Mea
sure
d R
ut D
epth
, inc
hes
Companion Sections Line of Equality Modified Sections
Expanding the Realm of Possibility14
Cracking
Neat MixesVersus
PMA Mixes
Expanding the Realm of Possibility15
What is the time difference between different amounts of cracking?
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
0.00 20.00 40.00 60.00 80.00
Fatigue Cracking - PMA Sections, %
Fatig
ue C
rack
ing
- Com
pani
on
Sect
ions
, %
Years for equal cracking?
Expanding the Realm of Possibility16
Fracture Damage AnalysisTensile strain at bottom of HMA layer.Neat sections individually calibrated & used to predict PMA cracking.
( )( )( ) ( ) 854.0291.3
1 1000432.0−−
=
E
CN
t
Mff
ε
HMA Wearing Surface
HMA Base
Granular Base
Subgrade
εt
⎟⎟⎠
⎞⎜⎜⎝
⎛−
+= 69.084.4
beffa
beff
VVV
M
Expanding the Realm of Possibility17
Fatigue Cracks – Neat Vs PMA
0102030405060708090
100
0 20 40 60 80 100
Predicted Fatigue Cracking, %
Mea
sure
d Fa
tigue
Cra
ckin
g, %
Companion Sites Sites with Modified Mixtures Line of Equality
Expanding the Realm of Possibility18
Transverse Cracking – Neat Vs PMA
0.050.0
100.0150.0200.0250.0300.0350.0400.0450.0500.0
0.0 100.0 200.0 300.0 400.0 500.0
Transverse Cracking - PMA Sections, ft.
Tran
sver
se C
rack
ing
- Com
pani
on
Sect
ions
, ft.
Expanding the Realm of Possibility19
Enhanced Performance Based on Damage Analysis
00.5
11.5
22.5
0 10 20 30 40 50
Age, years
Dam
age
Inde
x
Conventional HMA Mixtures PMA Mixtures
Material related distress.
Expanding the Realm of Possibility20
Expected Increase in Service Life, yrsSite Factor Condition Description Added Life
FoundationNon-Expansive 5-10Expansive 2-5Frost Susceptible – Cold Climate 2-5
Water Table & Drainage
Deep 5-10Shallow; Adequate 5-8Shallow; Inadequate 0-2
Existing Pavement Condition
HMAGood 5-10Poor-Extensive Cracking 1-3
PCCGood 3-6Poor-Faulting & Cracking 0-2
Expanding the Realm of Possibility21
Expected Increase in Service Life, yrsSite Factor Condition Description Added LifeClimate; Temp. Fluctuations
Hot Hot Extremes 5-10Mild 2-5Cold Cold Extremes 3-6
Traffic, Truck Volumes
LowIntersections 5-10Thoroughfares 3-6Heavy Loads 5-10
Moderate 5-10High 5-10
S1SP ARA0127-22
Summary Comments
Expanding the Realm of Possibility23
SummaryUse of PMA reduces distress in pavements & overlays
Less Fatigue CrackingFewer Transverse CracksSmaller Ruts
00.20.40.60.8
11.21.41.61.8
2
0 0.2 0.4 0.6 0.8 1 1.2
Rut Depths on PMA Sections, inches
Rut
Dep
ths
on C
ompa
nion
Se
ctio
ns, i
nche
s
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
0.00 20.00 40.00 60.00 80.00
Fatigue Cracking - PMA Sections, %
Fatig
ue C
rack
ing
- Com
pani
on
Sect
ions
, %
0.050.0
100.0150.0200.0250.0300.0350.0400.0450.0500.0
0.0 100.0 200.0 300.0 400.0 500.0
Transverse Cracking - PMA Sections, ft.
Tran
sver
se C
rack
ing
- Com
pani
on
Sect
ions
, ft.
Expanding the Realm of Possibility24
SummaryField & laboratory investigations of PMA
mixes suggest:Enhanced Performance
25 to 100 % increase in service life3 to 10 years increase in service life
Reduced Maintenance ActivitiesCrew SafetyEliminate Traffic Delays
Expanding the Realm of Possibility25
SummaryQuality of Construction –STILL IMPORTANT, IF NOT THE MOST IMPORTANT FACTOR.Many M-E Transfer Functions are stiffness based for binder & mix –OTHER MATERIAL PROPERTIES ARE MORE IMPORTANT.
Expanding the Realm of Possibility26
Thank you for your attention -Any questions?
Expanding the Realm of Possibility27
Expanding the Realm of Possibility
Expanding the Realm of Possibility29
Finding from Colorado Study
Use of PMA mixes extended the overlay service life over neat HMA mixes by:
3 years – 75 percentile value6 years – 50 percentile value