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

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

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. )

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)

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.

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

Influence Of Asphalt Tack Coat Materials Influence Of Asphalt Tack Coat Materials On The Interface Shear StrengthOn The Interface Shear Strength

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

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

Sample PreparationSample PreparationSample Preparation

Shear

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

)

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

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

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

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

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

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

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.

Variability of Air Voids and Variability of Air Voids and Mechanistic Properties of Plant Mechanistic Properties of Plant Produced Asphalt MixturesProduced Asphalt Mixtures

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

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

Testing ProgramTesting Program

Test section– Collect sufficient loose

mixtures from the paver– Mixture composition analysis– Compacted Samples

» Air voids» Mechanistic tests

Mobile Laboratory

InIn--Situ Test DevicesSitu Test Devices

FWDDynatest 800 model

PQI model 301TransTech System, Inc. LFWD – PRIMA 100 model

Carl Bro Company, Denmark

Laboratory Testing ProgramLaboratory Testing ProgramAir voidsAir voids

Cores and SGC samplesConventional– AASHTO T166

Vacuum Sealing Method– CoreLok– ASTM D 6752

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

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),

%

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

020406080

100120140160180200

ITS,

psi

SMA Super WC Super BC

SGCCore

ITS Test Results ITS Test Results –– Cores Cores vsvs SGCSGC

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

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

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

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

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

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

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

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

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

Louisiana Experience Louisiana Experience With Foamed Recycled With Foamed Recycled Asphalt Pavement Base MaterialsAsphalt Pavement Base Materials

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?

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

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

Foamed Asphalt Mixture DesignFoamed Asphalt Mixture DesignWirtgen Cold Recycling Manual

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 (%

)

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

Field TestingField Testing

c) FWDb) Geoguage

a) DCP e) LFWD

d) Dynaflect

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

Construction Cost and EconomicsConstruction Cost and Economics

Breakdown unit cost for the US 190 foamed asphalt RAP base job.

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

1998 Superpave1998 Superpave

Comparison of Laboratory and Field

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

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

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

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”