where are the superpave binder specifications headed. dangelo.pdf · where are the superpave binder...

Where are the SuperpaveBinder Specifications

headed.

John D’Angelo

Federal Highway AdministrationPresented at the 1st International Symposium

On Binder Rheology and Pavement Performance

August 14, 2000

Pre-Superpave Shortcomings

• Viscosity! viscous effects only

• Penetration! empirical measure of viscous and elastic effects

• No Low Temperature Properties Measured• Problems with Modified Asphalt

Characterization• Specification Proliferation• Long Term Aging not Considered

2525 6060 135135-15-15

ConsistencyConsistency(pen or(pen or vis vis))

hardhard

softsoft

penpenvisvis

visvis

AABB

CC

Temperature, CTemperature, C

Superpave Binder Specifications

• Performance Related Binder Spec for thepurchase of asphalt binders used in hot mixasphalt.

• Measure of the rheological properties of thebinders over a wide range of temperaturesand loading conditions.

• Developed as part of the Strategic HighwayResearch Program.

Superpave Binder Equipment

FatigueFatigueCrackingCrackingRuttingRutting

PAV - agingPAV - aging

RTFO - aging RTFO - aging No agingNo aging

Pavement AgePavement Age

ConstructionConstruction

[RV][RV][DSR][DSR]

Low TempLow TempCrackingCracking

[BBR][BBR]

[DTT][DTT]


• How do we make the specification worktoday?

Temperature Control isKey to the Superpave

Binder Specs.

Do we know what we have?

Temperature Control

• Current Specs. require +/- 0.1 oC control.! 0.1 oC can represent 2% error in the DSR.

• Most equipment does not meet this spec.! ISO 10012 requires precision of 0.03 for 0.1

control.

Temperature Control

Temperature Control

• Current specs will need to be changed.! The temperature shall be calibrated by a NIST

traceable device with measurement uncertaintyless then 1/3 of the required tolerance of themeasurement per (ISO 10012-1, par. 4.3). Fortemperature control of +/- 0.1Ε C thecalibration device uncertainty shall be +/-0.033Ε C

! This will require separate calibration.

Temperature Control

External temp. calibration will allowmost equipment to meet specs.


• Test Variability! PAV DSR.

• AMRL Jan 1995 Samples had CV 44%

• AMRL Jan. 2000 Samples had CV 22%.

! This is a dramatic improvement, but still needsgreater reduction.

• Experiment to evaluate using larger plates to reducevariability may lead to improved repeatability.


• PAV DSR.

! DSR testing with 8mm plate and 2 mm gap has2DS CV of 44%

! Preliminary testing with 12 mm plates and1mm gap has 2DS CV of 20%. This is mostlyfrom improved procedures. New procedures tobe sent to AASHTO.


• Silicone molds effect test results: time totest and the silicone cause variability.


• What are some of the changes to theequipment.

New Direct Tension Tester

Direct Tension Test

• Coefficient of Variation reported at over 30%or 2Ds 83%

• New Equipment and procedure trainingresults CV 10% or 2Ds of 27%.

Direct Tension Test

Old silicone molds effect results, caused early breaks.

Direct Tension Test

New metal molds and end pieces reduce variability.

Test Repeatability

• Through training and improved procedurestesting variability will continue to go down.

Revisions to Screening Tests

• Laboratory Asphalt Stability Test (LAST)! Measure storage stability with and without

agitation

• Modify RTFO! Better evaluates modified binders.

Laboratory Asphalt Stability Test

• AASHTO procedure is being developed forETG review.

165.0

Electric Motor25-27 RPM

TemperatureController

(Brookfield)

TemperatureProbe

Heater

Propeller(4 Blades)

Gas Purging

Sampling

Baffle

Modification of the RTFO• Modified binders do

not age in the RTFO

• Some modifiedsystems creep out ofthe bottle

• A uniform thin film isneeded to age bindersproperly

Modification of the RTFO

Steel Rod 126 mm Length 6-mm OD

Modification of the RTFO

• NCHRP study! Rods do not effect neat asphalt binders! Modified systems age 3 to 4 times the unaged

binders with rods.

• FHWA evaluation of procedure! Verification of research results.! Time to scrape bottles.! Effect of air during scraping time.

Mississippi SPS – 9 Project

• I 55, 3 binders same mix design, 2years and 2.4 million ESAL’s!58-22 exhibited 7 mm of rutting.

!64-22 exhibited 3 mm of rutting.

!76-22 exhibited no rutting.

Pennsylvania I80 Clearfield Co.

S Crack80-1927.8Gilsonite

80-2715.1SB

77-2516.4SBS

M Crack77-2120EVA

M Crack76-2023.2PE

M Crack67-2619.7AC-20

distressPG gradeG*sin∗ temp

AC Binder

Low Temperature Performance

• Lamont test sections.

SX ID # 1 3 4 5 6 7

CGSBGrading

80/100B 300/400A 80/100C 80/100A 150/200A 200/300A

Air blown Yes No No Yes No No

Field No Crack

-30.2 -35.9 -23.6 -26.1 -33 -35.9

Field Crack -33 -26.1 -35.9 -35.9

Current Spec -34.0 -38.8 -27.8 -37.5 -34.8 -40.0


• What is in the Future?! Not all binders of the same grade perform the

same.

! Not all modifiers are the same.

! The Superpave binder spec. has to be madeblind to modifiers.


• The BBR works well in determining unmodifiedbinders critical cracking temperature.! This has been verified on Canadian and US test sections

• Modified systems and some neat asphalts neednew tools to evaluated critical crackingtemperatures.

New Low Temp. Specification

• Combines the results of the BBR and DT.

Superpave Binder Specification

• New Low temperature specificationcombines the DT and the BBR.! Thermal stress is calculated from BBR data.

! Strength is determined from the DT.

! If the strength of the material is greater than the stressfrom the temperature drop the binder will not crack.

BBR test data for low temp. spec.

Low temp. stiffness master curve

Thermal stress compared to strength.

Specification Comparison

-40

-34

-28

-22

-16

-40 -34 -28 -22 -16

Current Spec

Pro

pos

ed S

pec

AAA-1 AAB-1 AAD-1 AAF-1 AAM-1

Lamont #1 Lamont #3 Lamont #6 Lamont #7

Proposed MP1a Spec.

Binder Tcr Current Spec Tcr Proposed Spec

70-22 Air Blown -24.5 -22.570-22 Conventional -25.1 -22.570-22 SBS Modified -26.0 -30.5Chemically Modified 64-28 A -29.0 -28.0Chemically Modified 64-28 B -27.5 -27.0Chemically Modified 64-28 K1 -29.5 -27.5Chemically Modified 58-28 M1 -27.3 -27.0Elvaloy Modified 64-34 DP -34.7 -36.0

Binder High Temp Properties

• I 80 Nevada Study same mix differentbinders.PG 64-22 mod. no rutting PG 64-22 unmod. 15mm rutting


• New test procedure to evaluate binders.

0.0

0.2

0.4

0.6

0.8

1.0

0 2.5 5 7.5 10

time, s

No

rma

lize

d S

tra

in

BM (PMA)

HSK(Conventional)

εacc HSK

εacc BM


Testing 3 different PG 82's

02468

101214

0 200 400 600 800 1000 1200

Time

Acc

umul

ated

Str

ain

SBRPEOxd

Superpave Binder Specification

• The Superpave Binder Specifications willcontinue to evolve.

• As findings from various studies becomeavailable the ETG will review these andmake recommendation for changes to theSpec.

Thank You

where are the superpave binder specifications headed. dangelo.pdf · where are the superpave binder...

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