Utilizing Field Data to Verify Performance Based ...€¦ · Dr. Walaa S. Mogawer, PE University of...

Utilizing Field Data to Verify Performance Based

Specifications for High Performance Thin Lift Overlay

Mixtures

July 18th, 2013 ▪ Laramie, WY

Dr. Walaa S. Mogawer, PE University of Massachusetts

Dr. Robert Kluttz Kraton Polymers

Definitions

High Performance Overlays (HiPO)

- Pavement preservation strategy

- Thickness equal to 1 inch or less

- Used in applications requiring higher levels of

rutting and fatigue resistance

50th Annual Peterson Asphalt Research Conference &

Pavement Performance Prediction Symposium 2013

Definitions Highly Modified Asphalt (HiMA)

- A new SBS polymer technology developed by Kraton

Polymers

- The SBS polymer loading is more than twice that of

ordinary modified asphalt, yet mixes are readily

workable and easy to lay in the field.

- The high polymer loading makes the asphalt more

like an asphalt-modified rubber than a rubber-

modified asphalt so it has many times the fatigue and

deformation resistance of ordinary modified asphalt.



Pilot Specification

A pilot regional specification for HiPO mixtures was

developed based on input and recommendations from

members of state transportation agencies of various

regional pavement preservation partnerships,

industry, and academia.

http://www.tsp2.org/pavement/other-information/research-pavement/

Pilot specification on AASHTO TSP2 web site:



Pilot Specification

Specification goal was to provide a guide that

could be utilized to develop better performing

preservation/ rehabilitation overlay mixtures

that addresses reflective cracking, low

temperature cracking, fatigue cracking, and

rutting issues encountered with conventional

overlays that shorten there service life.



Pilot Specification

- The pilot specification was tailored to address the

condition of the existing pavement.

- Provisions were provided to alter the HiMA

modification based on the level of severity of the

distresses of the existing pavement. A HiMA PG76-34

was recommended for roadways exhibiting only low

severity cracking. A HiMA PG82-28 was recommended

for roadways with little or no distress.



Pilot Specification

- The HiPO mixture was required to meet all the

Superpave 9.5 mm requirements listed in AASHTO

R35 and AASHTO M323.

- The amount of RAP in the mixture was limited to 25%

or the amount of RAP corresponding to 1% binder

replaced, whichever was less.



HiPO Mixtures with & without RAP

Property Device/Test Criteria

Thermal Cracking

Temperature of Mixture

Thermal Stress Restrained Specimen Test (TSRST) - AASHTO TP10-93

± 6°C from the low temperature performance grade of the binder

Cracking Overlay Test - TXDOT Tex-248-F

Average overlay test cycles to failure ≥300

Fatigue Life Flexural Beam - AASHTO T321

≥100,000 Cycles (750 micro)

Rutting

Asphalt Pavement Analyzer (APA) - AASHTO T340

Average rut depth for six specimens is ≤ 4 mm at 8,000 loading cycles

Added Requirement for HiPO Mixtures with RAP

Cracking Overlay Test - TXDOT Tex-248-F

Average overlay test cycles to failure within ±10% of the overlay test cycles to failure of control specimens without RAP

Pilot Specification Overview

Project Objectives

Assist three state DOT agencies (MnDOT,

NHDOT, and VTrans) in verifying HiPO

mixture designs developed by contractors

using the pilot specification.

Provide recommendations to refine the pilot

specification based on the performance of the

mixtures measured in the laboratory and after

two years service in the field.



Project Scope

Reclaimed Asphalt Pavement Highly Modified Asphalt (HiMA)

Aggregates

9.5mm HiPO



2011 Field Trial - Minnesota

Minnesota Department of Transportation (MnDOT)

had 1370 tons of HiPO incorporating 25% RAP placed

on a 1-3/4 mile northbound section of Trunk Highway

(TH) 100 west of Minneapolis (AADT = 64,000)



2011 Field Trial – New Hampshire

New Hampshire Department of Transportation

(NHDOT) had 1,500 tons of the HiPO incorporating

25% RAP on Route 202 in Rochester, NH (AADT =

4,600)



2011 Field Trial - Vermont

The Vermont Agency of Transportation (VTrans)

placed one mile of HiPO mixtures without RAP and

one mile of HiPO incorporating 25% RAP on US

Route 7 in Danby, VT.



Other Field Trials

1. Field trial conducted in Oregon in June

2012.

2. Field trial to be conducted in New Jersey in

2013.

3. Other trials planned during 2013

construction season.



2011 Field Trials – Existing Condition

- MN: Bad transverse cracks and potholes developing.

Milling to a depth of 1.5 inch or 2 inch was completed.

- NH: Pavement was in poor condition. No milling was

done prior to the placement of the mixture.

- VT: Pavement in 14th year of service and in “fair to good”

condition. Isolated areas of permanent deformation, some

transverse cracking and some shrinkage cracking. Surface

preparations included spot shimming of permanent

deformation areas, crack sealing along the length of the

project, patching of cracks wider than 1 inch and patching

of all potholes.



Experimental Plan Reclaimed Asphalt

Pavement (RAP)

Virgin Aggregates

HiMA Binders

1. 52-34 + 7.5% Polymer

2. 200PEN + 7.5% Polymer

Field Trials

1. Minnesota (MN)

2. New Hampshire (NH)

3. Vermont (VT)

Superpave HiPO

9.5 mm Mixture

Performance

Testing

Fracture

1. Overlay Tester

2. Flexural Beam Fatigue

3. Thermal Stress

Restrained Specimen

Test (TSRST)

Rutting

1. Asphalt Pavement

Analyzer (APA)

2. Hamburg Wheel

Tracking Device

Plant Produced

Mixtures

Mix Design

Verification



MN

Control & HiPO NH HiPO

VT HiPO

No RAP

VT HiPO

With RAP

Pilot Spec.

RAP, % 25% 25% 0% 24% 25% max.

Total Binder Content, %

5.3% 6.3% 6.8% 6.5% 6.5% min.

Virgin Binder Content, %

4.9% 5.3% 6.8% 5.5% -

Mixing Temperature

321-307ºF (161-153ºC)

340ºF

(171ºC) 351 -311ºF

(177-155ºC) 351-311ºF

(177-155ºC) -

Compaction Temperature

272-265ºF (133-129ºC)

300ºF

(149ºC) 310-291ºF

(154-144ºC) 310-291ºF

(154-144ºC) -

NDesign 90 75 65 65 -

Binder Grade Information

Base Binder PG Grade

Control PG64-28

HiMA

PG52-34

200PEN 200PEN 200PEN -

Target HiMA Binder PG Grade

PG76-34 PG76-34 PG76-34 PG76-34 PG76-34 PG82-28

Mixture Information

Mixture Gradations

Sieve

Size MN* NH

VT

No RAP

VT

With RAP

Pilot

Spec.

Pilot Spec.

Production

Tolerance

25.0 mm 100 - - - - -

19.0 mm 95.0 - - - - -

12.5 mm 83.0 100 100 100 100 ± 6

9.5 mm 62.0 98.8 99.0 98.0 90-100 ± 6

4.75 mm 50.0 68.4 83.0 81.0 ≤90 ± 6

2.36 mm 35.0 49.9 55.0 55.0 32 - 67 ± 4

1.18 mm 24.0 36.8 34.0 35.0 - -

0.600 mm 13.0 26.2 21.0 21.0 - -

0.300 mm 6.0 15.2 11.0 11.0 - -

0.150 mm 3.3 8.0 6.0 6.0 - -

0.075 mm 4.0 4.8 3.7 3.7 2 - 10 ± 1

RAP % 25% 25% 0% 24% 25% max. -

* Same gradation for MN control and HiPO mixtures.

Mixture Design Verification of Volumetric

Properties

MN

Control MN HiPO NH

VT

No

RAP

VT

With

RAP

Pilot Specification

(Refer to AASHTO

M323 Table 6)

Air Voids,% 4.9 3.8 2.0 3.2 2.7 4.0%

VMA, % 16.5 15.4 16.3 n/a n/a 15.0% min.

VFA, % 70.5 75.4 87.9 n/a n/a 65-75



Mixture Design & Volumetric Properties

MN gradation did not meet pilot specification

(9.5mm). MN followed an existing 12.5mm

mixture gradation specification.

NH and VT mixtures did not meet all volumetric

targets.



Fracture Performance Testing

Reflective Cracking - Texas Overlay Tester

Thermal Cracking –TSRST

Fatigue Cracking - Beam Fatigue

Fatigue Cracking - Semi-Circular Bending (SCB)

Test (Not In Spec.)



Reflective Cracking - Overlay Tester

Diagram from: Zhou et al. “Overlay Tester: Simple Performance Test for Fatigue Cracking” Transportation Research Record: Journal of the

Transportation Research Board, No. 2001, Transportation Research Board of the National Academies, Washington, D.C., 2007, pp. 1–8.

- Test Temperature = 15ºC (59ºF)

- Test Termination at 2,000 cycles or 93% Load reduction

- Testing in accordance with Tex-248-F



Thermal (Low Temperature) Cracking -

TSRST

- Cooling Rate of -10ºC/hour

- Testing in accordance with AASHTO TP10-93



Fatigue Cracking – 4pt Flexural Beam

Fatigue - Testing and Analysis in accordance

with AASHTO T321

- Test Temperature = 15ºC (59ºF)

- Pilot specification states that strain level should be equal to the strain in the existing HMA layer.

- If existing strain unknown, use:

750 micro strain for PG76-34 500 micro strain for PG82-28



Semi-Circular Bending (SCB) Test

SCB Test Setup

- Proposed standard test method was used

in this study (Mohammad (2005)

- Different notch depths utilized

- Test temperature = 25ºC

- Loading rate = 0.5mm/min

- Calculating the critical strain energy

release rate, Jc

a = the notch depth

b = sample thickness

U = the strain energy to failure



Type Reflective Thermal Fatigue Fatigue

Mixture Meets All Cracking Criteria in

Pilot Spec.?

Test Information

Average

Overlay Test (OT) Cycles to Failure

TSRST

Avg. Low Cracking

Temperature

Beam Fatigue Nf to 50%

Reduction in Stiffness

Semi-Circular Bending (SCB)

Test

Pilot Specification

Criteria

Average cycles to

failure ≥300 or within ±10% to control

specimens without RAP

± 6°C from the low

temperature performance grade of the

binder

≥100,000 Cycles at750 μstrain for

PG76-34 HiMA & 500 μstrain for PG82-28

HiMA

Not in Spec.

Critical Value of J-integral (Jc) kJ/m2

MN Control 133 -32.2ºC 26,004 0.40 NO Reflective & Fatigue

MN HiPO 434 -31.8ºC 336,019 0.40 YES

NH HiPO 2,000 -33.1ºC 348,266 Not Tested YES

VT HiPO No RAP 2,000 -30.1ºC 794,790 0.45 YES

VT HiPO With RAP 1,144 -27.8ºC 383,065 0.36 NO Reflective & Thermal

Fracture Test Results

Rutting Performance Testing

Asphalt Pavement Analyzer (APA)

Hamburg Wheel Tracking Device (HWTD) –

Not in Specification



Rutting – Asphalt Pavement Analyzer

- Test Temperature of 60ºC (140ºF)

- Testing in accordance with AASHTO T340

- Test Length of 8,000 cycles



Rutting - Hamburg Wheel Tracking Device

(HWTD) - HWTD testing conducted in

accordance with AASHTO T324

- Water temperature of 50ºC (122ºF)

- Test duration of 20,000 cycles



APA and HWTD Rutting Results

Test Asphalt

Pavement Analyzer (APA)

Hamburg Wheel Tracking Device (HWTD)

Mixtures Meets

Rutting

Criteria in Pilot Spec.?

Test Information

AASHTO T340

Conducted at the Standard PG High Temperature for

the Project Location

AASHTO T324

Conducted at 50ºC

Pilot Specification

Criteria

Average rut depth for six

specimens is ≤ 4 mm at 8,000

loading cycles

Not in Spec. - Average Rut at 10,000 Cycles

Not in Spec.-

Average Rut at 20,000 Cycles

MN Control 6.20 mm 2.11 mm 10.53 mm No

MN HiPO 5.92 mm 1.60 mm 11.58 mm No

NH HiPO 5.16 mm 4.20 mm 12.91 mm No

VT HiPO No RAP 2.03 mm 2.55 mm 8.98 mm Yes

VT HiPO With RAP 2.87 mm 1.26 mm 2.70 mm Yes

Field Trials – Condition 2 Years In-Service

- MN: Some transverse cracks have reflected through

the overlay, however the cracks are tight. The cracking

in the HiPO section are slightly less than the control

and visible rutting was not noted.

- NH: HiPO is performing well with minimal cracking

returned. The conventional mixture is estimated to

have 25% of cracking returned.

- VT: No apparent distress in either test sections



Project Observations

1. Refine specification to make the RAP characterization tests

mandatory. Require RAP characterization tests completed

prior to the mixture design verification. (asked contractors to

characterize RAP, but it didn’t happen.)

2. The reflective cracking OT results for mixtures with and

without RAP indicated the pilot specification criteria of ±10%

agreement between the two mixtures results may be too

stringent. This criterion will be monitored as testing of future

field trials continue and correlated with field observations.




3. Field observations from Minnesota suggested that reflective

cracks noted in the HiPO and control mixtures may be due to

the severity of existing cracks after milling coupled with the

fact they were not treated. Refine specification in the surface

preparation section to include provisions to seal cracks prior to

mixture placement.

4. The flexural beam fatigue data indicated that all the HiPO

mixtures were able to meet the specification of >100,000 cycles

to failure at 750 micro-strain. Refine the strain level used for

this testing to be the strain experienced at the actual field

location.




5. Only two of the four HiPO mixtures were able to meet the APA

rutting requirement. Since the field data after two years in

service did not indicate any rutting in any mixture, it is

suggested that this criterion be monitored as testing of future

field trials continue and correlated with field observations to

determine if the specification threshold should be changed.

6. Since not all state agencies have access to an APA, it is

suggested to expand the specification to include another rut

testing device like the HWTD and corresponding rutting limits

should be set and included in the specification.



Acknowledgements

The following people have been instrumental in completing the

research presented here:

Commercial Asphalt Co. – Minnesota

Pike Industries - New Hampshire

Continental Paving - Vermont



THANK YOU!



Utilizing Field Data to Verify Performance Based ...€¦ · Dr. Walaa S. Mogawer, PE University of...

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