characterization of fracture resistance of rpmac mixtures ...spave/old/technical...4000 6000 8000...
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Characterization of Fracture Characterization of Fracture Resistance of RPMAC Resistance of RPMAC
Mixtures Using a SemiMixtures Using a Semi--Circular Bend Fracture TestsCircular Bend Fracture Tests
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Objective and ScopeObjective and ScopeEvaluate the fracture resistance of Superpave mixtures containing RPMAC using the SCB test 19 mm Superpave mixture4 binder blends– Blend 1: 100% PG 70-22M
» SBS elastomeric polymer modified asphalt cement (PMAC)– Blend 2: 80% PG 70 - 22M + 20 % RPMAC– Blend 3: 60% PG 70 - 22M + 40 % RPMAC– Blend 4: 40% PG 70 - 22M + 60% RPMAC
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LTRC SemiLTRC Semi--Circular Bend (SCB) TestCircular Bend (SCB) Test
Sample Geometry – 150mm X 57mm– Four specimens
Three notch depths– 25.4 mm– 31.8 mm– 38 mm
Test temperature– 25 oC
0
5 0
1 0 0
1 5 0
2 0 0
2 5 0
3 0 0
3 5 0
0 0 . 0 2 0 . 0 4 0 . 0 6 0 . 0 8 0 . 1
2 5 .4 mm notc h3 1 .8 mm notc h
3 8 mm notc h
De f l e c t i on ( i n. )
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SCB Test ResultsSCB Test Results
y=-0.314x+1.51 y=-0.017x+0.97 y=-0.28x + 1.36 y = -0.037x + 1.83R2 = 0.8988 R2 = 0.8225 R2 = 0.9906 R2 = 0.9954
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
20 25 30 35 40
N o tch (mm)
0% 20% 40% 60%
0% 20% 40% 60% PG70-28 CRA PG70-22
AC-5 + 9% SEBS
AC-5 + 2% Elvaloy
0.55 0.30 0.40 0.65 0.54 0.65 0.42 0.40
Current RPMAC Study Mull et al., 2002 Bhurke et al., 1997
Jc
(kJ/m2)
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SummarySummary
Semi-circular bend test provides a simple means to obtain fracture resistance characterization of asphalt mixturesSCB provides stable testing configurationThe critical fracture resistance values (Jc) fromthe SCB tests were fairly sensitive to changes in binder stiffness. Increased percentages of RPAMC in themixtures exhibited higher JcSemi-circular bend test can be used as a valuable correlative tool in predicting fatigue crack growth of asphalt mixtures.
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Future WorkFuture WorkPerform an extensive testing program– specimen geometry– environmental conditions– on the values of JIc obtained using the semi-circular
bend specimen.
Produce a standardized method by which JIc can be used as a material parameter to rank the static fracture resistance of asphalt mixtures
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Influence Of Asphalt Tack Coat Materials Influence Of Asphalt Tack Coat Materials On The Interface Shear StrengthOn The Interface Shear Strength
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Objective Objective Evaluate the current practice of using tack coats through controlled laboratory shear tests
Evaluate the influence of tack coat types, application rates, and test temperatures on interface shear strength
Recommend optimum tack coat type and application rate
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ScopeScope19 mm Mix
Tack Coat MaterialsCRS-2P
SS-1
CSS-1
SS-1h
PG 64-22Asphalt Cements PG 76-22M
Emulsions
0.200.900.100.450.050.230.020.090.000.00
gal/yd2l/m2
Application Rates
131557725°F°C
Test Temperatures
Triplicate samples156 samples
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Sample PreparationSample PreparationSample Preparation
Shear
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Test ProcedureTest ProcedureTest Procedure Shear Stress vs DisplacementTest Temperature 550C
0
10
20
30
40
50
60
0 2 4 6 8 10 12
Displacement (mm)
Shea
r Str
ess
(kpa
)
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Variation of Shear Strength Variation of Shear Strength Versus Application Rate at 25Versus Application Rate at 25ººCC
050
100150200250300350400
Shea
r Str
engt
h (k
Pa)
0 0.09 0.23 0.45 0.9
Application Rate (l/m2)
PG 64-22PG 76-22MCRS-2PSS-1CSS-1SS-1h
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Variation of Shear Strength Variation of Shear Strength Versus Application Rate at 55Versus Application Rate at 55ººCC
0102030405060
Shea
r Str
engt
h (k
Pa)
0 0.09 0.23 0.45 0.9
Application Rate (l/m2)
PG 64-22PG 76-22MCRS-2PSS-1CSS-1SS-1h
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Maximum Interface Shear StrengthMaximum Interface Shear Strength
050
100150200250300350400
Max
She
ar S
treng
th
(Kpa
)
PG 6
4-22
PG 7
6-22
M
CR
S-2P
SS-1
CSS
-1
SS-1
h
Tack Coat Type
Test Temperature 25°C0.09 l/m20.23 l/m2
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Maximum Interface Shear StrengthMaximum Interface Shear Strength
0
10
20
30
40
50
60M
ax S
hear
Stre
ngth
(K
pa)
PG 6
4-22
PG 7
6-22
M
CR
S-2P
SS-1
CSS
-1
SS-1
h
Tack Coat Type
Test Temperature 55°C0.09 l/m20.23 l/m20.45 l/m20.90 l/m2
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Maximum Interface Shear StrengthMaximum Interface Shear Strength
0
10
20
30
40
50
60M
ax S
hear
Stre
ngth
(K
pa)
PG 6
4-22
PG 7
6-22
M
CR
S-2P
SS-1
CSS
-1
SS-1
h
Tack Coat Type
Test Temperature 55°C0.09 l/m20.23 l/m20.45 l/m20.90 l/m2
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Summary and ConclusionsSummary and ConclusionsControlled laboratory simple shear tests – optimum application rate
The influence of tack coat types, application rates, and test temperatureson the interface shear strengthAmong the six different tack coat materials used, CRS 2P emulsion was identified as the best performer Optimum application rate for CRS 2P emulsion was 0.09 l/m2 (0.02 gal/yd2)At 25C, increasing the tack coats application rates generally resulted in a decrease in interface shear strengthAt 55C, the interface shear strength was not sensitive to the application rateCRS 2P at the optimum application rate provided only 83 percent of the monolithic mixture shear strength Suggests that the construction of flexible pavements in multiple layers introduces weak zones at these interfaces
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RecommendationsRecommendationsFurther Research is Recommended to
Validate laboratory interface strength measurements by conducting similar simple shear tests on field cores;
Examine the variation of interface strength under fatigue;
Evaluate the influence of tack coats at interfaces between: an asphalt concrete and a Portland cement concrete layer, and between a new construction surface and an old one; and
Determine optimum application temperature and curing period for different tack coat types.
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Variability of Air Voids and Variability of Air Voids and Mechanistic Properties of Plant Mechanistic Properties of Plant Produced Asphalt MixturesProduced Asphalt Mixtures
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Objectives
Evaluate the variability of Air Voids of Plant Produced MixturesCompare different methods of air void measurements Characterize SGC samples and field coresAssess the in-situ test measurements
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ScopeScopeTwo overlay rehabilitation
Projects– I-10 Egan
» 25.0 mm Superpave Mixture, Binder Course
» 12.5 mm Superpave Mixture, Wearing Course
– I-10 Vinton» SMA mixture
Test Sections– 6: I-10 Egan – 1: I-10 Vinton
2” SMA (12.5mm)7” 25mm-Superpave
10” Rubblized PCC
Silty Clay Subgrade(AASHTO A-6)
2” 12.5mm-Superpave7.5” 25mm-Superpave
10” Rubblized PCC
Silty Clay Subgrade(AASHTO A-6)
EganVinton
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Testing ProgramTesting Program
Test section– Collect sufficient loose
mixtures from the paver– Mixture composition analysis– Compacted Samples
» Air voids» Mechanistic tests
Mobile Laboratory
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InIn--Situ Test DevicesSitu Test Devices
FWDDynatest 800 model
PQI model 301TransTech System, Inc. LFWD – PRIMA 100 model
Carl Bro Company, Denmark
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Laboratory Testing ProgramLaboratory Testing ProgramAir voidsAir voids
Cores and SGC samplesConventional– AASHTO T166
Vacuum Sealing Method– CoreLok– ASTM D 6752
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Laboratory Testing ProgramLaboratory Testing ProgramMechanistic TestsMechanistic Tests
Indirect Tensile Strength Test– 25°C– Each test section:
» One Core and SGC sample» Six
– Analysis: ITS
FSCH– AASHTO TP7 – 48°C and 60°C– Each test section:
» One Core and SGC sample» Six
– Analysis: G* and δ
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Relationship of Air Voids Test MethodsRelationship of Air Voids Test Methods(Conventional (Conventional vsvs CoreLok)CoreLok)
y = 1.05xR2 = 0.92
0
2
4
6
8
10
12
0 2 4 6 8 10 12Air Voids (Conventional), %
Air
Voi
ds (C
oreL
ok),
%
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Relationship of Air Voids Test MethodsRelationship of Air Voids Test Methods(PQI vs. Conventional / CoreLok)(PQI vs. Conventional / CoreLok)
y = 1.01xR2 = 0.49
y = 1.05xR2 = 0.59
0
2
4
6
8
10
12
14
0 2 4 6 8 10 12Air Voids, %
Air
Voi
ds (P
QI)
, %
ConventionalCorelok
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020406080
100120140160180200
ITS,
psi
SMA Super WC Super BC
SGCCore
ITS Test Results ITS Test Results –– Cores Cores vsvs SGCSGC
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y = -13.9x + 251.1R2 = 0.74
0
50
100
150
200
250
0 2 4 6 8 10
Air Voids (%)
ITS
(psi
)
Cores
IDT Strength IDT Strength vsvs Air VoidsAir Voids
y = -13.6x + 277.9R2 = 0.47
0
50
100
150
200
250
0 2 4 6 8 10
Air Voids (%)
ITS
(psi
)
SGC Samples
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Variation of G* Variation of G* –– I 10 EganI 10 Egan12.5 mm Mixture 12.5 mm Mixture –– 48 C48 C
14758
02000400060008000
1000012000140001600018000
G*
at 1
0Hz
(psi
)
S1 S2 S3 S4 S5 S6 Avg
Core– Mean = 14758 psi– SD = 1310 psi– CV = 9 %
Core25992
0
5000
10000
15000
20000
25000
30000
G*
at 1
0Hz
(psi
)
S1 S2 S3 S4 S5 S6 Avg
SGC– Mean = 25992 psi– SD = 3604 psi– CV = 14 %
SGC
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0
5000
10000
15000
20000
25000
30000
35000
G* (1
0Hz)
, psi
SMA Super WC Super BC
SGCCore
FSCH Test Results, G*FSCH Test Results, G*(10Hz) (10Hz) atat 48 48 ooCC
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Complex Shear Modulus (G*Complex Shear Modulus (G*10Hz10Hz))((SGC vs. CoreSGC vs. Core))
y = 1.57xR2 = 0.88
0
10000
20000
30000
40000
0 10000 20000 30000 40000
G* at 10Hz (Core), psi
G*
at 1
0Hz
(SG
C),
psi
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Variation of FWD Results Variation of FWD Results –– I 10 EganI 10 Egan25 mm Mixture 25 mm Mixture
0
100
200
300
400
500
600
Test Section
FWD
Def
lect
ion
(mic
ron)
d1d1-d6d7
S-1 S-2 S-3 S-4 S-5 S-6
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y = -1.38x + 397.3R2 = 0.80
0
100
200
300
400
500
0 50 100 150 200 250 300
LFWD Deformation Modulus (ksi)
FWD
Def
lect
ion
Relationship Between FWD and LFWD Relationship Between FWD and LFWD –– d1d1--d6d6
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ConclusionsConclusionsAir VoidsAir Voids
Binder course mixtures had the highest air voids variation as measured by all three methods, followed by the wearing course and SMA mixturesCoreLok air voids variation were slightly than the conventional methods Strong correlation between air voids measured using Conventional and CoreLok methodsCorrelations between PQI measured air voids and other two methods (CoreLok and AASHTO T-166) are fair
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ConclusionsConclusionsMechanistic TestsMechanistic Tests
Binder course mixtures had the highest ITS & G* variations followed by the wearing course and SMA mixturesCores showed better correlations to air voids than SGC samples Cores and SGC samples showed Similar variations– ITS, G*
The ITS and G* of SGC samples were higher than cores Good correlation was observed between the G* of the cores and SGC samples
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ConclusionsConclusionsMechanistic TestsMechanistic Tests
Good correlations were observed between ELFWD and FWD deflections d1 and d1-d6 LFWD test may be used as an alternative to FWD testing in pavement structure evaluation
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Louisiana Experience Louisiana Experience With Foamed Recycled With Foamed Recycled Asphalt Pavement Base MaterialsAsphalt Pavement Base Materials
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The Project StatementThe Project Statement
Route: US 190, Baton Rouge, LouisianaCRCP concrete pavement design called 8”stone baseField jobs include the removal of the existing asphalt overlay and original concrete pavements (RAPs and waste concretes)Question:
1. What’s the strength of the foamed asphalt treated RAPs ?
2. Can it be used in place of the designed stone base?
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Objective Objective
Assess the potential use of foamed asphalt (FA) treated RAP as a base course material in lieu of a crushed lime stone base
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ScopeScope
Laboratory foamed asphalt (FA) RAP mixture design
Field Evaluation: In-situ test device- Dynamic cone penetrometer (DCP) - Humboldt Stiffness Geoguage (HSG)- Falling Weight Deflectometer (FWD)- Light Falling Weight Deflectometer (LFWD)- Dynaflect
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Foamed Asphalt Mixture DesignFoamed Asphalt Mixture DesignWirtgen Cold Recycling Manual
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Foamed Asphalt Mixture Design (Foamed Asphalt Mixture Design (Contd..Contd..))Optimum FA Content: 2 percent
Foamed asphalt vs Retained ITS
100
102
104
106
108
110
1.0 1.5 2.0 2.5 3.0Foamed asphalt content (%)
Ret
aine
d IT
S (%
)
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Field Test SectionField Test SectionTest Section Layout - US Highway 190
A B C A
8 " Stone base
Section A Section B Section C
8 " F.A.* RAP** base
1000 ft 1000 ft
8" Lime treated subbase 8" Lime treated subbase 8" Lime treated subbase
4" F.A. RAP base4" F.A. RAP+25% crushed concrete
Subgrade Subgrade Subgrade
* F.A. Foamed Asphalt** RAP Recycled Asphalt Pavement
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Field TestingField Testing
c) FWDb) Geoguage
a) DCP e) LFWD
d) Dynaflect
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Comparison Of FA Treated BasesBase A : Crushed Lime Stone Base B : Foam Asphalt with 100% RAPBase C : Foam Asphalt with 75% RAP& 25% Crushed Concrete
0.0
1.0
2.0
3.0
4.0
Stiff
ness
Rat
io
HSG LFWD DCP FWD
Stiffness Ratio of B/AStiffness Ratio of C/A
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Construction Cost and EconomicsConstruction Cost and Economics
Breakdown unit cost for the US 190 foamed asphalt RAP base job.
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Summary and ConclusionsSummary and ConclusionsA pilot Study on the performance of FA stabilized RAPThree base materials:
– Stone, FA stabilized, FA/CC stabilized
Field test sections were constructedSet of in-situ test devicesAll five in-situ test devices were sensitive to the difference of base materialsFA treated RAP showed higher in-situ stiffness values and structure numbers than those of lime stone base layer No significant difference in the measured field stiffness
– 100 percent RAP– 75 percent RAP and 25 percent crushed concrete.
The addition of 1.5 percent of Portland cement resulted in a higher soaked ITSSimilar observation was noted form field strength testsCost effectiveness
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1998 Superpave1998 Superpave
Comparison of Laboratory and Field
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Densification of Level 3 WC from Traffic
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
7.0
7.5
8.0
0 5 10 15 20 25 30 35 40 45
Months
% A
ir Vo
ids
US 90 GBUS 61 (0045)US 90 WBEI-20 BCUS 61 (0044)Avg. all jobs
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5 yr IRI
4045505560657075
1 2 3 4 5
year
IRI,
in. p
er m
ilecontractor Ahwy121
contractor Bhwy4
contractor Chwy353
contractor Dus90
contractor Ewb expway
contractor Fscenic hwy
contractor BI20.sma
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5 yr Rut Depth
0.00
0.05
0.10
0.15
0.20
0.25
1 2 3 4 5
year
Rut
, in.
contractor Ahwy121
contractor Bhwy4
contractor Chwy353
contractor Dus90
contractor Ewb expway
contractor Fscenic hwy
contractor BI20.sma
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Field Performance of SuperpaveField Performance of Superpave
IRI measured with Laser Profilograph –All jobs Excellent (< 80)Rut measured–Maximum measurement after
5 years of traffic = 0.15”
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