Superpave Superpave Contractor’s PerspectiveContractor’s Perspective

California Asphalt Pavement ConferenceCalifornia Asphalt Pavement Conference

Adam J.T. Hand, PhD, PEAdam J.T. Hand, PhD, PE

Ontario, CAOntario, CA April 24, 2013April 24, 2013

Outline Experiences

Academic – UNR, WRSC, WT, Purdue Industry – GCI, Several RolesService – SP ETG, NCHRP, AAPT, NAPA, …

Lessons Learned MaterialsLabs and Equipment ImplementationLab vs. FieldProduction & Construction

Context – Superpave and QC/QA All at Once

Lessons Learned Things We Worried About:

Aggregate Properties (CAA, FAA, FEP)Mix Design VerificationRestricted Zone

PMBs How to Handle RAP Performance Testing Tenderzone

Lessons Learned Asphalt Binder Specification – Chemical Goal

Physical Property Spec - Huge Improvement Still - PG+, MSCR, PPA, CRM, TB

Aggregates Not Big Change in California – Early 1990’sRestricted Zone – Guide

ARZ, BRZ, TRZ can ALL Perform WellSome Sand May Be NeededWashed Crusher Fines, Chips?P200 Must Be Managed – Mix Sensitivity

ASTM STP December 2000

p200 Management - 19mm Example

012

34567

89

10

4.0 5.0 6.0 7.0% AC

% A

ir V

oids

At Target p200 = Solid LinesAt Field Observed p200 = Dashed Lines

Reduction in AC at 4.0% AV = 0.8% due to +1.5% p200

Reduction in AV at Opt AC = 1.8% due to +1.5% p200

Lessons Learned

Δ from AASHTO Standards = Challenging…NDesign

Min VMA (increase vs. production)D/A (smaller NMAS mixes)FEP (3:1)T283 (conditioning and minimums)Adding Conflicting Requirements

Use or Generate Data via Shadow Specs First

Everything is Bigger in the Lab Bigger Samples (4x)

Bigger EquipmentMore Square Footage$ Investment

SGC 4800g

Hveem1200g800lbs - Really?

Everything is Bigger in the Lab

Everything is Bigger in the Lab

Compactors and Verification Superpave Center and ETG – SGC’s

10 yearsSGCs are NOT all the same

SGC Frame ComplianceInternal Angle Verification NeededDON’T Buy a Headache!!!Follow Your Owner?

Superpave Center – Mix VerificationAggregates BatchingDust Correction

Will Now Know Source of Δ

Everything is Bigger in the Lab HWTD

Hamburg Wheel Track Device (HWTD) Colorado →Texas, … (Rutting and Stripping) Slabs or paired cylindrical samples, 7 ± 2% AV (Cores OK) 8”diam x 1.75” steel wheel, 50pass/min, 158lb load 50ºC and 20k passes or ½” rut depth, SIP 50ºC and PG64 (5k), PG70 (10k), PG76 (20k) ≤ ½” r & R not yet published

AASHTO T324 Hamburg Test Method ILS by AMRL

SGC 4800g

Hveem1200g

ILS AMRL Prepared all Samples Only Cutting and Test Method Variability

9.5mm 19mm

AASHTO T324 Hamburg ILS

AASHTO T324 Hamburg ILS Observations

Very Significant Variability in Results Between LabsDid Not Publish Precision Statement

Conduct Ruggedness Experiment First Key Factors Affecting Results:

Starting location of the wheelWheel track alignment on the sampleNumber of sensors and sensor locationsGyratory sample cutting and mold

Closely Inspect your New Equipment Utah DOT Similar Experience – Great Job Addressing

Before Implementation Encourage Similar in California

Dry Tensile Strengths vs. Binder Grade

Date of Design AgencyMethod/Sample

DiameterLaboratory Who Performed

Testing

Mix Design Nominal

Maximum SizeBinder Grade

Aggregate Source

Ant-Strip Method

Dry Tensile Strength (psi)

3/25/2010 Caltrans Hveem/4” Construction Materials Engineers 12.5mm PG 64-28PM Source ALime Slurry Marination

86

1/31/2012 NDOT Hveem/4” NDOT 19.0mm PG 64-28NV Source ALime Slurry Marination

100

1/31/2012 NDOT Hveem/4” NDOT 19.0mm PG 64-28NV Source ALime Slurry Marination

76

5/29/2012 FAA Marshall/4” Eastern Sierra Engineering 12.5mm PG 64-28 Source ALime Slurry Marination

71

8/24/12 NDOT Hveem/4” NDOT 19.0mm PG 64-22 Source ALime Slurry Marination

125

10/1/2012 Caltrans Hveem/4” Construction Materials Engineers 9.5mm PG 64-28TR Source ALime Slurry Marination

77

3/1/2013* Caltrans Hveem/4” Construction Materials Engineers 19.0mm PG 64-28 Source ALime Slurry Marination

84

3/22/2013* Caltrans Superpave/6” GARCO - Stockton 19.0mm PG 64-28 Source ALime Slurry Marination

94

*- The 3/22/2013 Superpave 6” diameter dry tensile strength data was performed using the same gradation and optimum asphalt content obtained from the 3/1/2013 Hveem design as to permit a direct comparison of sample size vs. dry tensile strength.

Min Dry Tensile Strength

Dry Tensile Strength = f(PG Binder Grade)

Mix TypeAggregate

SourceBinder Type

Asphalt Content (BDW)

Compaction Method

Dry Tensile

Strength (psi)

Hamburg Rut Depth @ 15,000 passes (in)

Hamburg Inflection

Point (No. of Passes)

¾” HMA Source A PG64-28 5.5 Hveem – 4” 84 n/a n/a

¾” HMA Source A PG64-28 5.5 Gyratory– 6” 94 0.1 >25,000

¾” HMA Source A PG70-10 5.5 Gyratory– 6” 211 n/a n/a

• Dry Tensile Specification > 120 psi• Hamburg Rut Depth < 0.5in after 15,000 passes• Hamburg Inflection point – min. 10,000 passes

Tensile Strength Specimens under Tensile Stress/Strain What Material Can Resist Tension? Key Drivers of Tensile Strength

BondBinder Stiffness

Should PG70- 10 vs. PG64-22 vs. PG64-28 all have same TSDry?

Binder Stiffness vs. Grade (1/2 or 2x) NCHRP Report 444, "Compatibility of a Test for

Moisture-Included Damage With Superpave Volumetric Mix Design“No Difference in Hveem and Superpave TS

Impacts of Lab Turnaround Time Function of:

Project Location/LogisticsTest MethodAvailable Resources

Test and TimeVolumetrics and In-Place Density ≈ 1-2 daysWTD ≈ 3 daysTSR ≈ 7 days

Risk (Production TSR Example)≈ 2000 to 4000 tons/ day x $100/ton in-place

Over $1M per week (2kx$100x7days) – WOW!How to Address Risk?

Plant Production Aggregate Plant Balance? VSI Crushers? RAP Fractionation?

Treat Like Aggregate Additional Feed Bins and ControlsDrive with Acceptance Criteria

Volumetric SpecificationsSensitivity to p200

More Washing?Baghouse Controls?

Aggregate BreakdownSGC = Plant?How Addressed?

ASTM STP December 2000

p200 Management - 19mm Example

012

34567

89

10

4.0 5.0 6.0 7.0% AC

% A

ir V

oids

At Target p200 = Solid LinesAt Field Observed p200 = Dashed Lines

Reduction in AC at 4.0% AV = 0.8% due to +1.5% p200

Reduction in AV at Opt AC = 1.8% due to +1.5% p200

Aggregate Breakdown Mix Design to Post-Plant (Lab to Field) Must Consider in

Mix Design Process Production Start-up Gradation Acceptance

Does Breakdown in Lab Mixer and SGC = Breakdown in Drum or Dryer and Pugmill?NO

What Gradation Should be Used in Mix DesignStockpile, Hot Bin, Coldfeed?

What Gradation Should be Used for Acceptance?Coldfeed, Hot Bin, or Post-Plant?

24

What About Production? Lab Mix Design to Field Production

Differences are Real – Must Address What Occurs During Production that Affects

Gradation and Volumetrics?Breakdown in the Drum (p200 ↑) If p200 ↑ Post Plant what will be Done to Maintain

4.0% Air Voids, …?Reduce %AC?

� Reduced Durability� Is this Good or Bad?

%AC

Ru

ttin

g

Du

rab

ility

Lab Mix Design to Field Production Mix Design Purpose? How to Address Δ’s - What is End Goal? End Product Quality

Field Adjust AC and Grad to Desired Volumetrics

Appropriate TV Δ’s P200 dosing in MD? Test Strip %AC, Gradation, Volumetrics – Same Sample …

Aggregate Breakdown Example

0

10

20

30

40

50

60

70

80

90

100

Percent Passing

Sieve Size ^ 0.45 Power (mm)

Hot Bin Blend

Ignition Oven Gradation

Spec Limit

Target Values

0.0750.15

0.30 0.60 1.18 2.36 4.75 9.50 12.5 19.0

Over 5% on coarse sieves and 2% on p200

Asphalt Binder Set Point Verification (Hot Drop)

Plant Set Point = Mix Design OBCIn-Spec – Go to ProductionOut-of-Spec - Repeat, Repeat, Repeat

ProductionPlant Setpoint = Mix Design OBC

Standard Process � if PSP and OBC Δ ≤ 0.4% OK� If PSP and OBC Δ ≥ 0.4% Shut Down

QC/QA � if PSP and OBC Δ ≥ 0.0% PWL Compomised� Typical σT = 0.20

Lab Mix Design to Field Production

Lab to Field No %AC Set Point Change?

Impact on Volumetrics

Impact on %AC PWL/PFσ%AC = 0.20 typical (CT, AMRL, …)Off Target, no Set Point or TV Δ

%AC Pay Factors for Spec Tolerances = ±0.4%

0.75

0.80

0.85

0.90

0.95

1.00

1.05

0.00 0.10 0.20 0.30 0.40 0.50

Standard Deviation

Pay

Fac

tor

Offset = 0Offset = 0.1Offset = 0.2Typical Variability

1.01

0.95

%AC Pay Factors for Spec Tolerances = ±0.3%

0.75

0.80

0.85

0.90

0.95

1.00

1.05

0.00 0.10 0.20 0.30 0.40 0.50

Standard Deviation

Pay

Fac

tor

Offset = 0Offset = 0.1Offset = 0.2Typical Variability

0.94

0.83

Superpave Experiences 2005

Stockpile ManagementPre-Superpave

Superpave Experiences -32

Stockpile ManagementPost-Superpave

Additional Feeder Bins RAP Fractionation 12 Bins at 1 Hot Plant?

Accurately Metering Baghouse Fines?

Wasting Baghouse Fines?

Superpave is Technology Friendly Can Technically Address in Lab

Neat, PMBRAPRASWMA…

We Can Field Produce

Field Observations NMAS

¾” has ¾” Rock in It t/NMAS ≥ 3, Max by Density Measurement

BRZ can = Segregation (everywhere) & Workability Challenges – Training and QC Critical

Density Matters!!!Get All but 1.5% ImmediatelyFewer PneumaticsTenderzone (not something new)

Truck Loading Focus MTV’s Joints

Field Observations Have Compacted up to 5.5” Lift with ¾” NMAS We Can Place and Compact Superpave Mixes

Tenderzone - special Kneeding compactors?

Training is Critical to Success!

Training Needs

Significant Training Required:Professional and TechnicalMix Designers and TechniciansEstimating StaffPlants StaffConstruction Operations Staff Inspection StaffAgency/Contractors/Engineering Firms

Consider FHWA Efforts in Early 1990’s

My Gut Importance of Training Will Be WAY Under Estimated Lab Investment will Be Too Slow - Logistics Issues? Issues with Differences in Caltrans and AASHTO and

City/County Specs – Design, Equipment, Acceptance, Mix Management, … will ExistGrad+D/A Spec, Grad +Vol Independent SamplesHWTD, Dry Tensile Strength, Lab to Field

Could Have HWTD Challenges if Not Patient Could Not Address Aggregate Breakdown and Mix

Sensitivity Some Aggregate Sources will Be Challenging Required Plant Investments will Be Underestimated There will Need to Be Specification Iterations

Moving Forward Superpave = HUGE Step ForwardSuperpave = HUGE Step Forward Late Adoption will Eliminates Others Early ChallengesLate Adoption will Eliminates Others Early Challenges InvestmentInvestment

LabsLabsPlant $ – VSI’s, RAP Feeder Bins, Baghouse ControlsPlant $ – VSI’s, RAP Feeder Bins, Baghouse Controls

Con Ops – No ProblemsCon Ops – No Problems Technology – RAP, RAS, WMA, … friendly - JDITechnology – RAP, RAS, WMA, … friendly - JDI Get Lab Equipment and Methods Right FIRSTGet Lab Equipment and Methods Right FIRST We Will All Need to Continually ImprovementWe Will All Need to Continually Improvement

Binder, Mix Design, Perf Tests, Mix to Structural Binder, Mix Design, Perf Tests, Mix to Structural Design, Test Methods and SpecificationsDesign, Test Methods and Specifications

We Will Make Better Products and That Will Be Good for We Will Make Better Products and That Will Be Good for Our IndustryOur Industry

QuestionsQuestions