nchrp project 9-54 long-term aging of asphalt mixtures for ......oven aging of loose mixture at...
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NCHRP Project 9-54Long-Term Aging of Asphalt
Mixtures for Performance Testing and Prediction
Asphalt Mixture & Construction Expert Task GroupFall River, MA
5/8/2018
Y. Richard Kim, Cassie Castorena, Michael Elwardany, and Farhad Yousefi Rad
North Carolina State University
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Outline
NCHRP 09-54 Objectives Proposed Long-Term Aging Procedure Current Efforts
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NCHRP 09-54 Objectives
Develop a calibrated and validated procedure to simulate long-term aging of asphalt mixtures for performance testing and prediction
Develop a pavement aging model as a function of climate, age, and pavement depth
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Development of the Proposed Long-Term Aging Procedure
Selection of the aging method• Compacted specimen vs. loose mixture• Oven vs. pressure aging vessel
Selection of the aging temperature• 95ºC vs. 135ºC
Determination of required aging duration• Climate, depth, age
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Criteria for Selecting the Aging Method
Specimen integrity• Compacted specimen
(38-mm and 100-mm) • Geometric and air void
changes • Oxidation gradient • Performance
• Loose mix• Compactability• Performance
Efficiency Practicality and versatility
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Aging Gradient in Compacted Specimen
3.0
3.5
4.0
4.5
5.0
5.5
log
G* a
t 64°
C, 1
0 H
z (P
a)
NC 9.5-mm mixture (PG 64-22, no RAP)
4.63 4.71 4.82
Core Mid-Layer Outer-Layer
Oven, Large Spec., 85°C, 8 days
28%20%
Oven, Small Spec., 85°C, 8 days ≈
Oven, Loose Mix, 85°C, 5.25 days6
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Compaction of Aged Loose Mixture 60
52 57
0
10
20
30
40
50
60
70
80
90
Num
ber o
f com
pact
ion
gyra
tions
to
ach
ieve
4%
targ
et a
ir vo
ids
Short-term AgedOven, Loose Mix, 85°C, 8 daysOven, Loose Mix, 95°C, 21 days
1E+02
1E+03
1E+04
1E+05
1E-09 1E-05 1E-01 1E+03
|E*|
(MPa
)
Reduced Frequency (Hz)
Short-term AgedOven, Loose Mix, 85°C, 8 daysOven, Loose Mix, 95°C, 21 days
0.0
0.2
0.4
0.6
0.8
1.0
0.0E+00 5.0E+05 1.0E+06 1.5E+06 2.0E+06
C
S
***
Loose mixture oven aging selected!
FHWA ALF SBS (PG 70-28, no RAP)7
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Selection of Laboratory Aging Temperature
Increasing temperature expedites oxidation Aging above 100ºC has raised several
concerns• Thermal decomposition of sulfoxides• Disruption of binder microstructure• Binder/Mastic drain-down
Performance implications of aging above 100ºC unknown
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Experimental Approach
Three mixtures considered: FHWA ALF SBS, SHRP AAD, and SHRP AAG
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1E+01
1E+02
1E+03
1E+04
0 200 400 600
G* (
kPa)
Aging Duration (Hours)
Loose Mix Aged at 95°CLoose Mix Aged at 135°C
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Chemistry vs. RheologyFHWA ALF-SBS
log G* = 41.384 (C+S) + 1.5819
log G* = 25.8756 (C+S) + 2.5129
3.5
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
0.07 0.08 0.09 0.1 0.11 0.12
log
G* (
Pa)
Carbonyl + Sulfoxide Absorbance Peak (AU)
Short-term AgedOven, Loose Mix, 70°COven, Loose Mix, 85°COven, Loose Mix, 95°COven, Loose Mix, 135°CField Core, 8 Years Old
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Performance Test Results
SHRP AAD-1
Short-term AgedOven, Loose Mix, 135°C, 16.8 hoursOven, Loose Mix, 95°C, 8.9 days
1E+2
1E+3
1E+4
1E+5
1E-8 1E-6 1E-4 1E-2 1E+0 1E+2
|E*|
(MPa
)
Reduced Frequency (Hz)
0.0
0.2
0.4
0.6
0.8
1.0
0.0E+0 4.0E+5 8.0E+5 1.2E+6
C
S0E+00
1E+04
2E+04
3E+04
4E+04
5E+04
0E+00 5E+04 1E+05 2E+05
Cum
ulat
ive
(1-C
)
Nf (Cycle)
(c)
Loose mixture oven aging at 95ºC selected!
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Determination of the Aging Duration
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Field Sections
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log 𝐺𝐺∗ = log𝐺𝐺0∗ + 𝑀𝑀(1 −𝑘𝑘𝑐𝑐𝑘𝑘𝑓𝑓
) 1 − exp −𝑘𝑘𝑓𝑓𝑡𝑡 + 𝑘𝑘𝑐𝑐𝑀𝑀𝑡𝑡
𝑘𝑘𝑓𝑓 = 𝐴𝐴𝑓𝑓 exp �−𝐸𝐸𝑎𝑎𝑓𝑓𝑅𝑅𝑅𝑅 ,
𝑤𝑤ℎ𝑒𝑒𝑒𝑒𝑒𝑒
𝐺𝐺∗= shear dynamic modulus at age t,
𝐺𝐺0∗ = shear dynamic modulus at short-term aged condition,
NCHRP 9-54 Kinetics Model
𝑀𝑀 = binder aging rate,
𝑘𝑘𝑐𝑐 = 𝐴𝐴𝑐𝑐 exp �−𝐸𝐸𝑎𝑎𝑐𝑐𝑅𝑅𝑅𝑅 , and
𝑅𝑅 = temperature in Kelvin.14
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Required Duration to Match Field Aging
Field (EICM) Lab Oven Aging
95°C
AgingDuration?
log 𝐺𝐺𝐹𝐹𝐹𝐹𝑒𝑒𝐹𝐹𝐹𝐹∗ = log 𝐺𝐺𝑜𝑜∗ + 𝑀𝑀[(1 − �𝑘𝑘𝑐𝑐 𝑘𝑘𝑓𝑓) 1 − exp −𝑘𝑘𝑓𝑓𝑡𝑡 + 𝑘𝑘𝑐𝑐𝑡𝑡]𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹
log 𝐺𝐺𝐿𝐿𝐿𝐿𝐿𝐿∗ = log 𝐺𝐺𝑜𝑜∗ + 𝑀𝑀[(1 − �𝑘𝑘𝑐𝑐 𝑘𝑘𝑓𝑓) 1 − exp −𝑘𝑘𝑓𝑓𝑡𝑡 + 𝑘𝑘𝑐𝑐𝑡𝑡]𝐿𝐿𝑎𝑎𝐿𝐿
[(1 − �𝑘𝑘𝑐𝑐 𝑘𝑘𝑓𝑓) 1 − exp −𝑘𝑘𝑓𝑓𝑡𝑡 + 𝑘𝑘𝑐𝑐𝑡𝑡]𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹𝐹 = [(1 − �𝑘𝑘𝑐𝑐 𝑘𝑘𝑓𝑓) 1 − exp −𝑘𝑘𝑓𝑓𝑡𝑡 + 𝑘𝑘𝑐𝑐𝑡𝑡]𝐿𝐿𝑎𝑎𝐿𝐿
Required aging duration to match field aging is
independent of binder source/type (i.e., STA G* and
M value)
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CAI = ∑𝐹𝐹=124 (𝐷𝐷 × 𝐴𝐴 × exp �−𝐸𝐸𝑎𝑎𝑅𝑅𝑇𝑇𝑖𝑖 /24) = 𝑡𝑡𝑜𝑜𝑜𝑜𝐹𝐹𝑜𝑜
whereD = depth correction factor,𝐴𝐴, 𝐸𝐸𝑎𝑎= fitting parameters,R = universal gas constant, T = pavement temperature (Kelvin), andd = depth of interest (mm).
𝐷𝐷 = �3.4311 𝐹𝐹−0.683 for 6 𝑚𝑚𝑚𝑚 ≤ 𝐹𝐹 ≤ 35 𝑚𝑚𝑚𝑚0.3026 for 𝐹𝐹 > 35 𝑚𝑚𝑚𝑚
Climatic Aging Index (CAI)
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y = 1xR² = 0.7142
0
5
10
15
20
25
30
0 5 10 15 20 25 30
Mea
sure
d D
urat
ion
at
95°C
(Day
s)
Climatic Aging Index, CAI
Surface Layer(6 mm)
20-mm depth
Deeper Layers(below 20 mm)
Climatic Aging Index (CAI)
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Aging Duration Maps for 6 mm Depth4 Years
8 Years
16 Years
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Aging Duration Maps for 20 mm Depth4 Years
8 Years
16 Years
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Aging Duration Maps for 50 mm Depth4 Years
8 Years
16 Years
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Validation of the Developed Aging Procedure
y = 0.9863x + 0.0461R² = 0.7674
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3
Fiel
d M
easu
red
log
G*
from
Fie
ld C
ores
Estimated log G* of Laboraoty aged Loose Mixture
LTPP-WA LTPP-CALTPP-OH MnROADNCAT-Control MIT-Control
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log G* of Laboratory Aged Loose Mixture
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Proposed AASHTO Standard
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Summary
Oven aging of loose mixture at 95ºC recommended
A climatic aging index (CAI) developed by simplifying the kinetics model prescribes the laboratory aging duration to match field aging as a function of hourly pavement temperature history and depth
Draft AASHTO standard developed for long-term aging of asphalt mixtures for performance testing
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Current Efforts
Refinement of the aging duration maps Finalization of pavement aging model Investigation of effects of binder aging on
asphalt mixture cracking performance
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Questions?
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