SAWS 2009-10-16 report v1 FP - aapaqtmr.org – Ian Reeves ... References – Henderson / Yeo paper...

Workshop Report

Friday 16 October 2009

12:00pm to 3:00pm

Charles Barton Auditorium,

10th Floor Spring Hill Office Complex

477 Boundary Road

Spring Hill

Queensland

Theme:

Bringing improvements in asphalt pavements to practice through new

design methods, evaluation of products and accelerated pavement

testing

PROVISIONAL AGENDA FOR WORKSHOP

When: Friday 16 October 2009, 12:00pm to 3:00pm

Where: Charles Barton Auditorium, 10th Floor Spring Hill Office Complex, 477 Boundary Road, Spring Hill, Queensland

Theme: Bringing improvements in asphalt pavements to practice through new design methods, evaluation of products and accelerated pavement testing

12:00 Registration and snacks 12:10 Welcome Ian Reeves - GM Engineering & Technology, TMR 12:15 Review of challenges to Queensland pavements & surfaces Dave Hubner TMR Peter Bryant TMR 12:30 Presentations by International guest participants

Dr Randy West – Director, National Centre for Asphalt Technology (NCAT) at Auburn University Dr Ramon Bonaquist – Chief Operations Officer, Advanced Asphalt Technologies, Virginia USA General Topics: • Role of NCAT in supplying performance evaluation of asphalt pavements through

accelerated testing and the advantages to Road Authorities and Road Builders • Update on the NCAT Pavement Test Track and associated development work

o Project reports: Use of high percentages of RAP / Perpetual pavement evaluation

o Structural assessment findings against mechanistic-empirical framework o Future plans, State participation and extra benefits of the accelerated

test facility • Validating the endurance limits for hot mix asphalt pavements

01:30 Questions and discussion on topics Ross Guppy facilitator 01:45 APT needs & options Mike Moffat ARRB 02:00 APT experiences in Africa Pablo Balmaceda Hyder 02:10 Workshop & discussion “What to do about knowing more about Queensland pavements?” ”Who should be involved?” “ List to the steps to be taken & timetable to deliver” Ross Guppy facilitator Process: There will be short presentations by local presenters and International Guests with facilitated discussion to improve understanding and to assess possible advantages for Queensland.

1

10/20/2009

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Accelerated pavement testing, evaluating products & new design methods 1

Workshop Meeting Reportincludes presentations x6 per page

Welcome – Ian Reeves

Road pavement challenges facing DTMR – David Hubner

Pavement Design Challenges – Peter Bryant

NCAT Test Track Overview – Dr Randy West

Plan for validating HMA pavement endurance limits – Dr Ramon Bonaquist

APT needs and options – Mike Moffat

APT in South Africa – Pablo Balmaceda

Workshop - directions

References – Henderson / Yeo paper at ET Forum 2009

Click on each title to show on screen or “right click” and save to your PC

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Accelerated pavement testing, evaluating products & new design methods 2

What do we need to do to better understand Queensland pavements?

1.State of flux – understand the problems

2.Establish competencies & knowledge requiredInvestmentInternal & external developmentHow do we organise and manage it

3.Where are we exposed - which roads- indentify (in network)

4.Perhaps can’t rely on methodology of the past

5.Design tools need rethinking- trial pavements - poor design methods

6.Look at the sources - don’t reinvent the wheel (ALF)

7. TSD data linked to pavement materials / type / GPR data

8. APT to characterize pavements- use potential future conditions?

9. Relook at pavement design models (subgrade up)

10. Micro-monitoring – data basesMacro – develop performance models

11. Awareness of imposed loads12. Budget allocation $15-20m / 5yrs

or $30m/10yrs13. USA work in asphalt

- potential savings in Qld14. Links to USA to learn from their

experience- Personal exchange – Scanning Tour- Share research - Sponsor APT sections

Normal Distribution Graphs_pavement performance.ppt 1

Heavy Vehicle_PBS_networ k access_research initiatives.ppt

TMR / AAPA Alliance Workshop16 Oct 2009

Welcome ‘sweat’ the pavements

Ian Reeves


MaterialsDocumentation

Standards

Design

Funding

Delivery

Planning

RainfallCompetence

RehabilitationMaintenance

Capability

Traffic

Environment

PAVEMENT DNA / GENETICS

Performance


76132262

417

719

1353

2456

3655

3329

1446

765

51

412

47 67

616

108 6 5

15

23

445

0

1000

2000

3000

4000

n/a >=-3 ,<-2 >=-2 ,<-1 >=-1 ,<0 >=0,<1 >=1 ,<2 >=2 ,<3 >=3 ,<4 >=4,<5 >=5 ,<6 >=6 ,<7 >=7 ,<8 >=8,<9 >=9,<1 0 >=1 0 PoorMtc e

LRPR Category (C ounts/km /yr)

Freq

uenc

y

0

25

50

75

100

Perc

ent >

= LR

PR V

aluePo or M tce Pa vs

No M ea nin gful D efa ul t L RPRDe fau lt L RP RFi lte red Poi nts R eg ressio n L RPRAll Po ints Reg ressio n L RPRNe tw ork Pro fil ePe rce nt >= LR PR (2n d Y a xis)

Good60%

P oor15%

Fair25%

Proba bility D ensity Func tion C umulative D ensity Func tion

A Class - GeneralB ClassC Class

Conceptual access classificationsD Class

1

Road Pavement & Surfacings Road Pavement & Surfacings Challenges facingChallenges facing

Qld DTMRQld DTMRBy David HubnerBy David Hubner

Single wide Single wide ––vv-- Dual tyresDual tyresBenefits = less noise, more payload (less truck Benefits = less noise, more payload (less truck weight), more efficient (less rolling resistance)weight), more efficient (less rolling resistance)Road wear = moderate to 500% increaseRoad wear = moderate to 500% increase

Road freight doubling over 20 yearsRoad freight doubling over 20 years PBS VehiclesPBS Vehicles

COAG objective COAG objective -- reduce transport costsreduce transport costs

Part of solution Part of solution –– encourage development encourage development of innovative vehicles to suit specific of innovative vehicles to suit specific industry needsindustry needs

Desirable road authority objective Desirable road authority objective ––reduce road wear/ton km carted reduce road wear/ton km carted

PBS PBS –– Tri & quad axles more efficientTri & quad axles more efficient

Axle groupAxle group Mass Mass (ton)(ton) ESAESA ESA/tonESA/ton

Single axle, single tyre Single axle, single tyre 66 1.511.51 0.250.25Single axle, dual tyresSingle axle, dual tyres 99 1.481.48 0.160.16Tandem axle, single tyreTandem axle, single tyre 1111 2.062.06 0.190.19

Tandem axle, dual tyresTandem axle, dual tyres 16.516.5 2.062.06 0.120.12TriTri--axle, dual tyresaxle, dual tyres 2020 1.381.38 0.070.07Quad axle, dual tyresQuad axle, dual tyres 2424 1.191.19 0.050.05

PBS PBS –– ideally less road wear/ton kmideally less road wear/ton km

Single trip ESA = 5.0Single trip ESA = 5.0 Single trip ESA = 6.3Single trip ESA = 6.3

Gross mass = 42.5 tGross mass = 42.5 t Gross mass = 62.5 tGross mass = 62.5 t

Pay load = 26 tPay load = 26 t Pay load = 40 tPay load = 40 t

Trips per 10,000 t freight = 385Trips per 10,000 t freight = 385 Trips per 10,000 t freight = 250Trips per 10,000 t freight = 250

ESAs per 10,000t freight = 1920ESAs per 10,000t freight = 1920 ESAs per 10,000t freight = 1575ESAs per 10,000t freight = 1575

2

PBS PBS –– suit specific industry needsuit specific industry need(Super B(Super B--doubles for bigger shipping containers)doubles for bigger shipping containers)

PBS PBS –– ideally below the blue lineideally below the blue line

Poor PBS Poor PBS –– high road wearhigh road wear

9 t 16.5 t 6 t9 t9 t

Weighted using 2004 SMVU national laden km travel

0

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

0 10 20 30 40 50 60 70 80 90 100 110 120 130 140

Gross mass (tonnes)

ESA

und

er p

resc

riptiv

e re

gula

tions

B1233

A123T23

R12R11 bus

R22

A111

A112

A113

R12T11

A123

B1232B1222

R22T22

R22T12R11T11R12T22

A123T23T23

R12T12

R11T1

R12T1

R12T2

A223T23A123T22

A123T22T23

A122

R11

Higher mass limits (HML)Higher mass limits (HML)

Better suspensions allow higher Better suspensions allow higher loads(around 10%)loads(around 10%)

Advantage = reduces transport costsAdvantage = reduces transport costs

Disadvantage = relies on good truck Disadvantage = relies on good truck maintenancemaintenance

Approved routes onlyApproved routes only

Higher axle loadsHigher axle loads

Transport benefits >> additional road wearTransport benefits >> additional road wear

Truck operator pays for additional wearTruck operator pays for additional wear

Voluntary basis onlyVoluntary basis only

Approved routes onlyApproved routes only

Issue Issue –– pavement performance????pavement performance????

3

Risks with higher axle loads

Existing legal axle load

New axle load

UNKNOWN

GoodOutcome

Potentiallypoor outcome

Catastrophicoutcome

Axle load

Monthlypavementdamage

on typicalroad

Qld has very thin pavementsQld has very thin pavementsHML Phase 2 – Lengths of In-situ Pavement Depth (mm) in Qld

0

200

400

600

800

1000

1200

1400

1600

1800

50 100<50 50-100 100-150 150-200 200-250 250-300 300-350 350-400 400-450 450-500 500-600

Thin pavementsThin pavementsLarge portion of network Large portion of network

Generally performing beyond expectationsGenerally performing beyond expectations

Remaining redundancy under existing axle loads is Remaining redundancy under existing axle loads is unknownunknown

Sensitive to climate & maintenance regime adoptedSensitive to climate & maintenance regime adopted

Impact of a lot more freight or higher axles loads is Impact of a lot more freight or higher axles loads is unknownunknown

Climate effectsClimate effects

Pavement InundationPavement InundationRoad closuresRoad closures

(varies (varies -- hours, days, months)hours, days, months)

4

Other Pavement design issuesOther Pavement design issuesTri & quad axle road wear Tri & quad axle road wear –– not based on sound not based on sound research (as per single & tandem axles)research (as per single & tandem axles)

Rapid loading by multiple axle vehicles Rapid loading by multiple axle vehicles –– not not accurately researchedaccurately researched

Dynamic load from each axle Dynamic load from each axle –– related road related road wear not fully understoodwear not fully understood

Surfacing shear loadings Surfacing shear loadings –– heavier trucks pulling heavier trucks pulling up grades, more tri & quad axles turning corners up grades, more tri & quad axles turning corners

Possible Solutions to pavement issuesPossible Solutions to pavement issues

Single wide tyresSingle wide tyresAssess overall impacts and benefitsAssess overall impacts and benefitsIf positive, limit use to ‘low wear’ single tyresIf positive, limit use to ‘low wear’ single tyresFurther improve ‘low wear’ aspectsFurther improve ‘low wear’ aspects

Freight doublingFreight doublingEncourage ‘low wear’ PBS vehiclesEncourage ‘low wear’ PBS vehiclesExtent PBS network (B triple network) Extent PBS network (B triple network) Allow high axle loads via ‘user pays’ Allow high axle loads via ‘user pays’

Possible Solutions to pavement issuesPossible Solutions to pavement issuesResearchResearch

Tri & quad axle road wear Tri & quad axle road wear –– Austroads projectAustroads projectMultiple axle rapid loading Multiple axle rapid loading –– Austroads projectAustroads projectDynamic loading Dynamic loading –– Austroads project & othersAustroads project & othersHigher axle loads, road pricing, optimum axle Higher axle loads, road pricing, optimum axle loadload

Numerical assessment Numerical assessment –– Austroads projectAustroads projectBasic research Basic research –– need new ALFs (several ALFs, need new ALFs (several ALFs, 1,2,3 & 4 axles, 100% overloads, lab and insitu 1,2,3 & 4 axles, 100% overloads, lab and insitu testing, many samples across network)testing, many samples across network)

Possible Solutions to pavement issuesPossible Solutions to pavement issuesResearch (continued)Research (continued)

Network Assessment technologyNetwork Assessment technologyfor opening road after inundation &for opening road after inundation &assessing long term freight carrying redundancyassessing long term freight carrying redundancy

•• Must be low cost and high speedMust be low cost and high speed•• high speed deflectograph (strength)high speed deflectograph (strength)•• ground penetrating radar (moisture & thickness)ground penetrating radar (moisture & thickness)•• Thornswaite index (climate)Thornswaite index (climate)•• pavement moisture sensitivity (sealed shoulders, low or pavement moisture sensitivity (sealed shoulders, low or

poorly drained formation, bound pavement, general geology, poorly drained formation, bound pavement, general geology, quality of maintenance) quality of maintenance)

Possible Solutions to pavement issuesPossible Solutions to pavement issuesResearch (continued)Research (continued)

Better surfacings Better surfacings -- SMA SMA –– Austroads projectAustroads project

Foam bitumen pavements Foam bitumen pavements –– Austroads projectAustroads project

Warm asphalt Warm asphalt –– Austroads projectAustroads project

Lack of binder in manufactured gravels Lack of binder in manufactured gravels –– rapid potholings rapid potholings -- add low add low amounts of cement/limeamounts of cement/lime

Bitumen quality Bitumen quality –– Austroads projectAustroads project

Sealing low trafficked roads Sealing low trafficked roads –– Cape seals?Cape seals?

Questions?Questions?

17/10/2009 Page 1

Flexible Pavement Design

Peter BryantPrincipal Engineer (Pavement Design)

Pavement Types in QueenslandTMR network length is 33,700 kmAbout 98% unbound granular or cement treated granular with thin bituminous surfacing (bitumen sealed or asphalt);Only about 2% are thick asphalt (more than just the surface) or concrete.

Traffic in QldAADT < 20 to AADT > 130,000

0

5

10

15

20

25

30

35

No Data

<= 99

100 t

o 249

250 t

o 999

1,000

to 4,

999

5,000

to 9,

999

10,00

0 to 1

4,999

15,00

0 to 2

4,999

25,00

0 to 3

9,999

>= 40,0

00

AADT Category

Perc

enta

ge o

f Que

ensl

and

Mai

n R

oads AADT T raffic Categ ory Len gth (km) Percentage

No Data 994 3.0<= 99 10,361 30.8

100 to 249 6,220 18.5250 to 999 8,463 25.1

1,000 to 4 ,999 5,490 16.35,000 to 9 ,999 899 2.7

10,000 to 14,999 432 1.315,000 to 24,999 394 1.225,000 to 39,999 264 0.8

>= 40,000 165 0.5TOT AL 33,683 100.0

Typical Heavy Duty Full Depth Asphalt Pavement in Qld

40 mm open graded asphaltPMB waterproofing seal50 mm size 14 mm dense graded asphalt (PMB)300 mm size 20 mm dense graded asphalt (C600)150 mm cement modified granular working plat.Selected fill &/or existing subgrade

Existing Design Models

Asphalt fatigue based on Shell (1978)

5

360 ⎥⎥⎦

⎤

⎢⎢⎣

⎡ +=

με S1.08) V6918(0.856 RF N .

mix

B

Future (& current) ChallengesDesigning beyond the intent of existing design proceduresIncreasing freight taskClimate ChangeNew materials, recycled materialsInnovationsMaintaining technical capabilityTraditional pavement types unsuitable or need improvement

17/10/2009 Page 2

Asphalt Fatigue Endurance Limit

Current designs have surpassed 500 mm of asphaltIs this beyond calibration of current design procedure?In 08/09 MR commissioned ARRB to undertake a literature review

Fatigue Endurance Limit

Source: AASHTO (1998)


Laboratory fatigue life is much greater at low strain levels than predicted by extrapolating performance at higher strain levelsExisting studies suggest a fatigue limit of 70 to 100 microstrainAn upper limit in asphalt thickness may be possible


Source: Nunn et al. (1997)

Conclusions

What do we need to do to better understand Queensland pavements?

Missed opportunities

1

at Auburn University

2

NCAT Pavement Test Track

3

The NCAT Pavement Test Track• 1.7 mile oval asphalt track• 45 experimental test sections, each 200 ft. long• Test sections are sponsored by highway agencies and

businesses to evaluate specific materials and/or pavement design strategies

• Realistic traffic applies 10 million ESALs in each two year cycle

• This year begins the 4th cycle of the test track

4

• Fine and coarse mixes perform similarly• Modified binders cut rutting approximately in half• Dense-graded mixes perform as well as SMA• Lower Ndesign is OK• Aggregate specifications

– F&E for SMA & OGFC– Polishing prone aggregates– Elimination of Restricted Zone– Gravel performs well in SMA & OGFC

• High RAP Mixes perform well

Test Track Research Findings

5

• Drainable, quite OGFC• Performance limits

– Air voids– Asphalt Pavement Analyzer– Flow Number

• Top-down cracking prediction methodology• Validation of pavement temperature models


6

• Mechanistic (σ-ε) models validated and calibrated – Measured vs. predicted HMA tensile stresses

and compressive stresses in unbound layers– Seasonal effects on pavement layers– Traffic wander– Transfer functions for strain damage– Speed vs strain / load pulse – Field fatigue thresholds– Atypical HMA response


2

The NCAT Test Track The 4th Cycle

2009 Group Experiment

Conventional Permeable Low Surface High Surface Foamed Additized Thiopave Thiopave Kraton UniqueDense Surface on RAP % RAP % Warm Warm Warm Warm Modified BinderHMA Dense HMA High Base High Base Mix Mix Sulfur Sulfur Mix Mix

Thickness Thickness Thickness

7 inches 7 inches 7 inches 7 inches 7 inches 7 inches 7 inches to be to be to be

Determined Determined Determined

ε-σ ε-σ ε-σ ε-σ ε-σ ε-σ ε-σ ε-σ ε-σ ε-σ

6 inches 6 inches 6 inches 6 inches 6 inches 6 inches 6 inches 6 inches 6 inches 6 inchesDGAB DGAB DGAB DGAB DGAB DGAB DGAB DGAB DGAB DGAB

Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade Stiff Subgrade

Funding from Private Sector Partners

9 10

Phase Two

HMA

Granu

lar B

ase

Subgra

de

Direction of Travel

HMA

Granu

lar B

ase

Subgra

de

Direction of Travel

HMA

Granu

lar B

ase

Subgra

de

Direction of Travel

(Timm et al., 2004)12

3

13 14

15 16

17

Pavement Performance Monitoring

18

0

1

2

3

4

5

6

7

8

9

10

11

12

0 2,500,000 5,000,000 7,500,000 10,000,000 12,500,000 15,000,000 17,500,000 20,000,000

Total Traffic Application (ESALs)

Ave

rage

Rut

Dep

th (m

m)

S6 S7 E2 E3

Rutting Comparisons

Coarse

Fine

Unmodified

Modified

4

19

Crack Mapping Full-Depth Experiment Objectives

• Evaluate the performance of each test section with regard to rutting, fatigue cracking, raveling, smoothness, etc.

• Evaluate responses of test sections in structural analyses– Refine models relating mix properties to structural

response of a pavement for any load and environment

– Link between lab properties and field performance

21

Lab Testing


Field Correlation of Performance Tests

• Permanent Deformation– NCAT Test Track– APA, Flow Number, E*

• Fatigue Cracking/Top Down Cracking– No experimental design– Fracture Energy, Bending Beam, TOT, Energy

Ratio– 2009 GE+ sections– AMPT Continuum Damage test

23

Asphalt Pavement Analyzer• Test procedure:

– AASHTO TP 63– SGC or field cores– Sample voids: 7±0.5%– Wheel load: 100 lbs– Hose pressure: 100 psi

5

Repeated Load Triaxial Permanent Deformation

• Test method – Developed under NCHRP 9-19– Lab prepared specimens

• Test equipment (AMPT or SPT)– Developed under NCHRP 9-29

• Development of rutting model– NCHRP 9-30A

Experimental PlanFn

Ndes 120lb / 120psi

7% 100lb / 100psi

7% 70psi / 10psi

N1 FL Super 67-22 0 12.5 6 6 3N2 FL Super 76-22 0 12.5 6 6 3N8 OK SMA 76-28 0 12.5 6 6 3

N10 MO Super 70-22 0 12.5 6 6 3S2 MS Super 76-22 15 9.5 6 6 3S6 TN 411-D 64-22 15 12.5 6 6 3

S7A IN Super 64-22 0 12.5 6 6 3S7B IN Super 64-22 0 12.5 6 6 3S8A IN Super 64-22 0 12.5 6 6 3S8B IN Super 64-22 0 12.5 6 6 3S11 AL Super 76-22 0 9.5 6 6 3S12 TX D-A 76-22 0 9.5 6 6 3

72 72 36No. of Test Sepecimens

APASect. Sponsor Mix Type Binder RAP% NMAS

APA Acceptance Criterion

r = 0.795, p-value = 0.002

0.0

2.0

4.0

6.0

8.0

10.0

12.0

0 5 10 15 20 25 30 35 40

Field Rut Depth (mm)

APA_

7%_1

00lb

/psi

_Aut

o (m

m)

APA_7%_100lb/psi_Auto Linear (APA_7%_100lb/psi_Auto)

APA Acceptance Criterion = 5.5 mm

9.5

Fn Acceptance Criteria

r = - 0.879, p-value = 0.004

0

200

400

600

800

1000

1200

1400

1600

1800

2000

0 5 10 15 20 25 30 35 40

Field Rut Depth (mm)

Fn_7

%_7

0psi

/10p

si (c

ycle

)

Fn_7%_70psi/10ps Linear (Fn_7%_70psi/10ps)

9.5

Fn Acceptance Criterion = 800 cycles

Permanent Deformation• APA

– Lab specimens compacted @ 7+/-0.5%– Automated measurement– Rut depth criterion = 5.5 mm

• Fn– 10 psi confining and 70 psi deviator stress– Francken model for determining Fn– Flow number criterion = 800 cycles

Flow Number vs. Rate of Rutting

y = 22817x-1.6739

R2 = 0.6742

0

1

2

3

4

5

6

7

8

9

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Flow Number

Rate

of R

uttin

g (m

m/m

illio

n ES

ALs

)

6

Proposed Flow Number Criteria(based on Fn vs. rate of rutting)

Traffic, ESALs Rut Threshold

9.5 mm 12.5 mm

1 million 105 89

3 million 202 171

5 million 274 232

7 million 335 284

10 million 414 351•Conditions: 58C, Confining Pressure = 70 psi, •Deviator Stress = 10 psi; Plant produced mixes

•Perpetual PavementsPerpetual Pavements Mechanistic-Empirical ApproachProfessor Marshall Thompson

• Combines the practicality of empirical methods with the technical soundness of mechanistic solutions.

• Uses mechanistic analysis, to determine the pavement responseto imposed loads…then applies “empirical” formulations (i.e. “transfer functions”) to determine the development of distressdue to the load-induced pavement response.

Max Tensile Strain

Pavement Foundation

High Modulus Mix(Varies As Needed)

Flexible Fatigue ResistantAsphalt Mix 3 - 4”

1.5 - 3” SMA, OGFC or Superpave

4”to6”

Zone of HighCompression

•Perpetual PavementsPerpetual Pavements Perpetual Pavement versus Conventional Design

7

Structural Design & Analysis

Temperature-Strain Relationship

N1y = 0.1049x1.9224

R2 = 0.788

N2y = 0.0053x2.5672

R2 = 0.7274

N3y = 0.1044x1.7348

R2 = 0.8987N4

y = 0.0072x2.3567R2 = 0.8656

N5y = 0.0281x2.1196

R2 = 0.9092

N7y = 0.0169x2.2355

R2 = 0.7454

N8y = 0.318x1.5002

R2 = 0.6389

N6y = 0.0412x2.0461

R2 = 0.9176

0

200

400

600

800

1000

1200

1400

40 50 60 70 80 90 100 110

Temperature

Stra

in, m

icro

stra

in N1

N2

N3

N4

N5

N6

N7

N8

Dr. David Timm


Mechanistic-Empirical DesignLoad Configurations

Material Properties

Layer Thicknesses

Mechanistic Model Stress, Strain, Deflection

211

k

kN ⎟⎠⎞

⎜⎝⎛=ε

Miner’s Hypothesis

∑=NnD

D>1?D<<1?

Yes

Final Design

No

at Auburn University at Auburn University

1

10

100

1000

10000

25 35 45 55 65 75 85 95 105 115 125

Mid depth Temperature, F

HM

A S

tiffn

ess,

ksi

N1N2N3N4N5N6N7N8

HMA Characterization

21

ββε Tt = 21

ββε Tt =

TeE 21

αα=

at Auburn University at Auburn University

8


2006 Structural Experiment Cross SectionsFL AL FHWA OK MO

Strain Instrumentation and Wireless Data Acquisition

Right Gauge

-300

-200

-100

0

100

200

300

400

500

0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9 2.1 2.3 2.5Time, sec

Long

tidin

al M

icro

stra

in


0

100

200

300

400

500

600

700

800

900

1000

35 45 55 65 75 85 95 105 115Mid depth Temperature, F

Long

itudi

nal H

oriz

onta

l Str

ain

N1

N2

N3

N4

N5

N6

N7

N8

Test Track Actual Response

21

ββε Tt =


Final Models• Thin Model (N1/N2)

• Rich bottom (N8)

• Thick Model (N3-N7)

6911.0007.3 )1()1(4814.0E

Nt

f ε=

6529.00312.3 )1()1(4875.0E

Nt

f ε=

5992.0063.3 )1()1(4831.0E

Nt

f ε=


Probabilistic Design – Monte Carlo Simulation

Thickness

f

Material Properties

f

Axle Weight

f

MonteCarlo

RandomSampling

MechanisticModel

Pavement Response

f % Below Threshold

% Above Threshold


9

• Design Pavement Structure to Limit Critical Strains» Minimize Tensile Strain with Pavement Thickness» Thicker Asphalt Pavement = Lower Strain» Strain Below Fatigue Limit = Indefinite Life

CompressiveStrain

Tensile Strain

Strain

Fatigue Life

IndefiniteFatigueLife

Design the Pavement Structure to Limit Critical Strains Fatigue Resistant Asphalt Base

» High Asphalt Content Mixes = Greater Strain Capability

» Modified Binders = Greater Strain Capability

Fatigue Life

Strain

High AsphaltContent

Low AsphaltContent

Indefinite Fatigue Life

Fatigue Resistant Asphalt Base

Laboratory versus Field Phase Three Methodology

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

22.0

24.0

N1 N2 N3 N4 N5 N6 N7 N8 N9 N10 S11

As

Bui

lt Th

ickn

ess,

in.

PG 67-22 PG 76-22 PG 76-22 (SMA) PG 76-28 (SMA)PG 76-28 PG 64-22 PG 64-22 (2% Air Voids) PG 70-22

Limerock Base Granite Base Type 5 Base Track Soil Soft Subgrade

Florida(new)

Alabama & FHWA(left in-place)

Oklahoma(new)

FHWA

Missouri(new)

Alabama(new)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 200 400 600 800 1000 1200 1400Microstrain

Perc

entil

e N1 (Top-down)N2 (Top-down)N3 (No crackng)N4 (No cracking)N8 (Cracked)N9 (No cracking)N10 (Cracked)S11 (Cracked)

•70 0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 200 400 600 800 1000 1200Microstrain

Perc

entil

e

N1 2003N2 2003N3N4N5 2003N6 2003N7 2003N1 2006N2 2006N8 2006N9 2006N10 2006S11 2006S13 2000

Distribution Comparison

• Criteria1. No fatigue cracking2. Substantial trafficking3. Not overdesigned

10

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0 100 200 300 400 500

Microstrain

Perc

entil

e Average+15-15N3N4

1

Advanced Asphalt Technologies, LLC

“Engineering Services for the Asphalt Industry”

NCHRP 9-44

Developing a Plan for Validating an Endurance Limit for HMA Pavements

Ramon Bonaquist, P.E.Chief Operating OfficerAdvanced Asphalt Technologies, LLC



Is There an Endurance Limit?

• Well documented field studies indicate that bottom-up fatigue cracking does not occur in thick flexible pavements.

• Laboratory studies support a change in the slope of the strain versus number of cycles relationships at low strain levels.



University of Illinois Data



Definition

• Endurance Limit for HMA Pavements is:

A level of strain below which there is no cumulative damage over an indefinite number of load cycles.



Project Objective

• To prepare a work plan and associated cost estimate for a future study to validate the endurance limit for asphalt concrete.



Approach

• Incorporate the concept of an endurance limit for HMA into a mechanistic-empirical algorithm for bottom initiated fatigue cracking in flexible pavements.

• Validate the methodology using performance data from full-scale pavement sections.

2



Hypothesis

• HMA does exhibit an endurance limit. • This endurance limit, however, does not reflect an

absence of load induced damage in the HMA. • It is the result of a balance of damage caused by

loading and healing or damage recovery that occurs during rest periods.



Threshold Strain

• Strain below which fatigue damage does not accumulate

• Depends on– Material properties– Temperature– Rest period



Pavement Design Objective

• Ensure that the damage induced by loading remains small enough so that healing occurs between traffic loads and there is no accumulation of damage over the life of the pavement

• Any pavement can be a perpetual pavement– Thicker pavements for heavier loads,

shorter rest periods, and poorer subgrade support



Threshold Strain Design

• Compute strain at the bottom of the asphalt layer.– Seasonal variations– Mixed traffic

• Compare to threshold strain.• Applied strain < threshold strain



Proposed Research

• Phase 1– Laboratory determination of threshold

strains– M-E Algroithm

• Phase 2– Field verification and caliabration



Laboratory ExperimentsExperiment Topic Factors

1 Mixture Compositional Factors Affecting Healing in HMA

• Binder Type • Binder Age • Effective Binder Content • Air Voids • Design Compaction • Gradation • Filler Content

2 Effect of Applied Strain on Healing

• Strain Level • Healing Rate From Experiment 1

3 Effect of Temperature and Rest Period Duration on Healing

• Temperature • Rest Period Duration

4 Development of Testing and Analysis Procedures to Determine Threshold Strain Levels

• Healing Rate From Experiment 1 • Mixtures From NCHRP 9-38

5 Estimation of Threshold Strain Levels from Mixture Composition

• Mix Compositional Factors Affecting Damage Accumulation

• Significant Factors From Experiment 1 • Temperature • Rest Period Duration

3



M-E Algorithm

• Variable threshold strains• Mixed traffic effects• Reliability



Field Verification/Calibration

• Accelerated Pavement Tests– Verify critical aspects of design procedure

• In-Service Pavements– Calibrate procedure



Accelerated Pavement Tests

• Verify Critical Aspects of Design Procedure– Engineering Reasonableness – Applicability of time-temperature

superposition to healing and allowable strains

– Independence of healing on applied strain– Effect of material properties on allowable

strains.



Recommended APT

• FHWA Pavement Test Facility• NCAT Test Track that have remained in

service from the first cycle through the current cycle

• NCAT Test Track Structural Sections• WesTrack• MNRoad



In-Service Pavements• Calibrate the Design Procedure

– Validate Concept of Endurance Limit

• Calibration Will Require Less Effort Than the MEPDG– No prediction of the extent of cracking– Either cracked or uncracked

• LTPP Sections Recommended– Monitoring over a number of years– Distress, deflection, and material property

data are available from the LTPP database Advanced Asphalt Technologies, LLC


Preliminary Calibration Matrix

Environment HMA Thickness,in

NoAlligatorCracking

LowAlligatorCracking

8 to 12 2 2Wet Freeze >12 2 28 to 12 2 2Wet No Freeze >12 2 28 to 12 2 2Dry Freeze >12 2 28 to 12 2 2Dry No Freeze >12 2 2

4



Progress

• Phase I Under Contract– NCRP Project 9-44A– Arizona State University, Matt Witczak PI– Started 9/1/2009– Completion data 2/28/2012



Questions

10/17/2009

1

APT needs & options

Michael Moffatt

www.arrb.com.au 2

www.arrb.com.au 3

uncertainty

www.arrb.com.au 4

time

certainty

today20 yearspast

20 yearsto come

www.arrb.com.au 5

MINIMUM THICKNESS OF BASE MATERIAL

1000

900

800

700

600

500

400

300

200

100

0

105 106 107 108

2

3

4

5

7

10

1520

≥30

CBR

ThicknessofGranularMaterial(mm)

Design Traffic (ESAs)

www.arrb.com.au 6

0

5

10

90/9

1

91/9

2

92/9

3

93/9

4

94/9

5

95/9

6

96/9

7

97/9

8

98/9

9

99/0

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9

09/1

0

$m (2

009

dolla

rs)

10/17/2009

2

www.arrb.com.au 7

certainty = f ( time, research )

www.arrb.com.au 8

Accelerated Pavement Testing

• increase load magnitude• increase load frequency• decrease pavement

www.arrb.com.au 9

Accelerated Loading Facilitywww.arrb.com.au 10

NSW17%

VIC25%

QLD17%

SA5%

shed36%

www.arrb.com.au 11

1985

Construction of Victorian section of Hume Hwy

• design traffic required very heavy duty pavement• needed a low risk solution• four main pavement options being considered:

rigid – jointed unreinforced concrete US$48/m2

asphalt on cement treated subbase US$46/m2

asphalt on unbound granular US$41/m2

two coat spray seal on unbound granular

US$26/m2

www.arrb.com.au 12

ALF test of actual construction in-situ undertaken:– test of new spray sealed granular pavement design– new high standards for construction– aimed to prove pavement could carry heavy traffic and

reduce risk

10/17/2009

3

www.arrb.com.au 13

Results:

• structural adequacy of the pavement was confirmed

• higher construction standards adopted elsewhere

• extensive lengths of this pavement type were constructed at a significant cost advantage compared to other designs

• BCR of 5.4 resulted from the research

• long term pavement performance monitoring commenced

www.arrb.com.au 14

uncertainty

www.arrb.com.au 15

2007

Need means of predicting performance of unbound materials

• marginal materials• recycled materials• modified & proprietary materials

www.arrb.com.au 16

www.arrb.com.au 17

Pavement plan

Rhyolite

150 mm Cemented

350 mm Unbound Granular

SandTuff

~50 m

Hornfels

Limestone

www.arrb.com.au 18

10/17/2009

4

www.arrb.com.au 19

uncertainty

www.arrb.com.au 20

www.arrb.com.au 21

2009

Need to better estimate pavement performance under new load types

• currently presume performance = deflection • don’t understand new configurations

www.arrb.com.au 22

crushedrock

clay

300 mm

400 mm

www.arrb.com.au 23 www.arrb.com.au 24

uncertainty

10/17/2009

5

www.arrb.com.au 25

Three different examples

Uncertainty reduced by

• ALF proof loading specific pavement• laboratory processes to predict material performance

– ALF demonstrated ‘true’ performance• Modeling to understand ink between axle type and

performance – ALF will provide performance

www.arrb.com.au 26

APT rocks! – I want one

What type?

• Dion: I’m a Wanderer• Pink Floyd: Wish You Were Here• Van Halen: Best of Both Worlds

www.arrb.com.au 27

uncertainty

www.arrb.com.au 28

certainty

www.arrb.com.au 29

Accelerated Loading Facility (ALF)

• linear track– no turning forces– 12 metre test strip

• half axle / dual tyres• sideways wander

– Normal distribution– 1 m wide

• 20 km/h• 60 kN load for this trial

– i.e. 50% overloaded– 1 cycle = 5 ESA

www.arrb.com.au 30

10/17/2009

6




10/17/2009

7




Monitoring

• NDM• Density• Moisture content

– Subbase– Bases

- Centreline- 1 m spacing

10/17/2009

8

www.arrb.com.au 43

Next….trafficking

www.arrb.com.au 44

The shed

www.arrb.com.au 45

The shed

www.arrb.com.au 46

Outline

• four unbound granular base materials have been selected for full scale testing

• ALF test pavements have been constructed and sealed

• proposed test program

www.arrb.com.au 47

0

5

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009

dolla

rs)

www.arrb.com.au 48

certainty = f ( time, research )

time < research + time

research < time + research

1

© Hyder Consulting Pty Ltd

AAPA Workshop – 16-Oct-2009

Accelerated Pavement Testing in Southern Africa

Pablo Balmaceda

© Hyder Consulting Pty Ltd 2

Contents

IntroductionHeavy Vehicle Simulator (HVS)Mobile Load Simulators (MLS and MMLS)ConclusionsRecommendations


Introduction

APT – Controlled loading to simulate long term in-service loading conditionsAccelerated accumulation of damageControlled testing environmentStarted with AASHTO road testThree types: full scale mobile, full scale fixed, and mobile Simulation of many years of traffic within weeks or months


Introduction

APT in South AfricaFirst HVS prototype: 1968Initiation of HVS programme with 3 HVS units: 1978Development of Multi-depth Deflectometer: 1980First TRH4 Guideline: 1980First draft of SAMDM: 1980 – Freeme, Maree, PattersonTesting on road and airport pavements: granular layers, GEMS, cemented layers, LAMBS: 1980 - 1993Development of temperature control chamber and new data acquisition system for HVS: 1993 – 1994


IntroductionAPT in South Africa (continued)

HVS testing on Caltrans Trial Sections in SA after sell of two units to Caltrans: 1994HVS testing on superlight pavements, porous asphalt: 1995Another HVS unit sold to the US Corps of Engineers: 1995Update of SAPMDM and THR4: 1996 - TheyseDevelopment of 3D stress sensor and laser profilometer: 1996 – 1997Delivery of a HVS units to RRL in Finland and Sweden: 1997Testing on various pavements types including LI built ones


IntroductionAPT in South Africa (continued)

Transfer functions developed for thin asphalt, thick asphalt (fatigue), granular (shear failure), cemented (fatigue and crushing), subgrade (permanent deformation), GEMS (shear failure), ETB (shear or fatigue), Foam Bitumen modified bases (shear of fatigue), UTCRCP.

2


HVS - GeneralOriginally developed in 1968More than 500 test sectionsHydraulically operated loading assembly carrying single/dual wheelWheel Loads from 20 to 100 kN at 14 km/h and 200 kN for airport pavements (Bigfoot)Track with: 1.5 m, track length: 8 mHVS test facilities in California, Florida, CRREL, Sweden-Finland

http://www.gautrans-hvs.co.za/© Hyder Consulting Pty Ltd 8

HVS - Monitoring and Instrumentation

HVS laser profiler RSD MDDPressure and strain transducersCAM

Stress in Motion MeterTermocouplesTrenchingData Capture and StorageThe DatabaseDCP


HVS – Monitoring and Instrumentation

Multi-depth Deflectometer (MDD)

Laser Profilometer

Road Surface Deflectometer (RSD)

Termocouples


HVS – Monitoring and Instrumentation

Stress-in-Motion (SIM)

Crack Activity Meter (CAM)Dynamic Cone Penetrometer (DCP)

Crack Monitoring

Trenching


Full Scale Mobile Load Simulator (MLS 10)

Established in 1998 by MLS Test Systems in Stellenbosch 20 APT research projects since 1998MLS10: 3m x 3m x 2.4m frame4 wheel bogies at 26 km/h, 7200 axle loads/hour - UnidirectionalHydraulically operatedIN 2004, APT in Mozambique



3



MLS 10 Testing at Manhica Test Sections

A closer view at MLS 10 Testing at Manhica Test Sections



Test Sections in Manhica, Mozambique, 2006


Model Mobile Load Simulator (MMLS 3)

Standarized field and laboratory set-ups Tests in dry heated or wet heated modes4 bogies, 1 axle/bogie, 1 wheel/axleMaximum tracking with: 80 mmLoad/wheel: 1900 @ 560kPa or 2700 @ 800 kPa. So loads are scales but real tyre pressures7,200 load applications/hourSuitable to explore performance of upper 125 mm of pavement



WATER BATH

CLAMP SCREW

CLAMP BRIQUETTE LONG. CLAMP

WHEEL RAMP

WATER INLET

DRY OUTLET

WET OUTLET

ADJUSTIBLE WEIR

OVERFLOW TANK

2360

900 DRIVE MOTOR

Φ300 PNEUMATIC TYRE

CRANK FOR HEIGHT SETTING

1260

363

80

Φ300 HOT WATER

INLET SUCTION OUTLET

PONDED WATER

LONGITUDINAL SECTION CROSS SECTION



SMA specimens after MMLS testing in the laboratory for King ShakaInternational Airport, Durban

Field MMLS testing on SMA at King Shaka International Airport, Durban


Conclusions

Numerous Technical Developments and Design Guidelines for a large array of pavement materials: subgrade, asphalt, granular (crushed stone, gravel, sands), CTB, ETB, GEMS, FBMB, UTCRCP in various pavement configurations, compaction ranges and environmental conditions.Overlay thickness designsInput on construction practices and specificationsInput on pavement materials mix designs and testingInput on quality control by better defining correlations between HVS tests and laboratory indicator testsSubstantial economic benefits from APT implementation

4


Recommendations

APT in Australia highly advisable:• To monitor different asphalt mixes: dense graded, open

graded, polymer modified, bitumen-rubber modified, warm asphalt techniques

• To monitor type and density of granular layers: Proctor versus Mod. AASHTO

• To assess modification / stabilization of granular materials: mechanical and with cementitious, bitumen emulsion, foam bitumen binders

• To determine pavement depth• To assess and, if required, amend construction

techniques and specifications


Recommendations

APT in Australia highly advisable (continued):• To minimize risk in implementing new technologes /

materials• Maximize the implementation of new technologies or

optimization of current technologies to avoid under- or over-designs.

Understand that the perceived high APT cost will result in substantial savings in pavement construction / maintenance and road user costs

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