Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis, December 14, 2010.

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Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis, December 14, 2010

Transcript of Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis, December 14, 2010.

Page 1: Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis, December 14, 2010.

Research Findings from the NCAT Test Track

APAI Winter ConferenceIndianapolis, December 14, 2010

Page 2: Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis, December 14, 2010.

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NCAT Pavement Test Track

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• 1.7 mile oval asphalt track• 45 experimental test sections, each 200 ft. long• A pooled-fund project with test sections 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

• Currently 60% complete with the 4th cycle

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Lab Testing

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• Fine and coarse Superpave mixes perform similarly

• Modified binders cut rutting approximately 50%, densify less under traffic, enable high binder content

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

Test Track Research Findings

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• Benefits of OGFC: safety, noise, smoothness• Lowering Ndesign is O.K.• High RAP content mixes perform well• Criteria for Lab Performance Tests

– Air voids– Asphalt Pavement Analyzer– Flow Number– Energy Ratio for top-down cracking

Test Track Research Findings

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• Mechanistic pavement models validated and calibrated – Measured vs. predicted HMA tensile stresses – Seasonal effects on pavement layers– Compressive stresses in unbound layers– Transfer functions for strain damage– Field fatigue threshold– Validation of pavement temperature models– Traffic wander– Speed vs strain / load pulse

Test Track Research Findings

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9Track Conference – 2/10/092006 Indiana Low QC Voids Study

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2006 Indiana Low QC Voids Study

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y = 98.74e-0.83x

R2 = 0.69

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5

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0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

QC Air Voids (% Gmm)

Max

imu

m M

easu

red

AR

AN

Avg

Ru

t D

epth

(m

m)

- All mixes shown produced with PG67 binder- Green control section placed in September 2006- Red treatment sections placed in October 2006- Blue replacement sections placed in February 2008- More rutting expected in blue replacement sections- Design gradations shown with round symbols- Closed gradations shown with triangle symbols- Black diamonds show PG67 RAP study sections- Yellow squares show 2000 limestone/slag mixes

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Track Layout

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2009 Thinner Structural Test Sections

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Perpetual Pavement on Soft Clay

N8 Strain = 21.487e0.0335*Temperature

R2 = 0.96

N9 Strain = 11.496e0.0298*Temperature

R2 = 0.9217

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Mid-Depth Temperature, F

Tens

ile M

icro

stra

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10”

14”

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Perpetual Pavement on Soft Clay

Visible Cracks on Pavement Surface

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0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0

IRI (

inc

hes

pe

r m

ile)

MESALs

N8 N9

Cracks appearon surface

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Perpetual Pavement on Soft Clay

• 14” pavement looks great after 16.2 million ESALs

• 10” pavement recently rehabilitated for 2nd time– In need of 1st rehabilitation after 10 million ESALs– 5” mill/inlay failed again after 3.5 million ESALs– 1.6 million ESALs on 5-3/4” high polymer inlay

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Perpetual Pavements

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• 24 inch perpetual (original) Track foundation• Designed with ‘93 Guide for MANY cycles

• Two 9 inch thick structural sections in 2003• ‘93 Guide predicted failure near 10M ESALs• 26.2M ESALs to date (perpetual expectation)

• 15 inches of wasted (excess) thickness?

• 14 inches required on N9 soft subgrade

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Layer Coefficient Recalibration

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1,000,000 10,000,000 100,000,000 1,000,000,000

ESALs

HM

A D

ep

th (

in)

a1 = 0.44a1 = 0.5418.5% Thinner

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Layer Coefficient Recalibration

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• Technology has improved since AASHO Road Test

• Need to recalibrate coefficients• Increase a1 from 0.44 to 0.54 based on all

structural sections on the Track• 18.5 percent thinner structural designs• Alabama saving $25M to $50M annually

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2009 Group Experiment (+)

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2009 Group Experiment (+)

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High RAP Mixes on the NCAT Test Track

• 2006: – 45% RAP surface mix with four different virgin

binder grades• 2009:

– 2006 high RAP sections continued– 45% RAP surface mix from Mississippi– 50% RAP HMA & 50% RAP WMA in structural

sections

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Group Experiment – High RAP (N10 & N11)

Control HMA Section

50% RAP Section

50% RAP WMA Section

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PFC Surface Cracks (Tack Method)

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PFC Surface Cracks (Tack Method)

• 2006 crack susceptible dense Superpave mix– Surface cracks after 1.9M ESALs (Rehab at 5.6M)

• 2009 PFC surface placed with conventional tack– Surface cracks after 2.2M (cracking/pumping at 6.2M)

• 2009 bonded PFC surface placed with spray paver– Surface cracks after 4.1M (very good at 6.2M)

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PFC Surface Permeability

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PFC Surface Noise

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SBS vs GTR Mill/Inlay: Rutting

GTR

SBS

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Pavement Preservation (S13)

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Temperature Reduction (S13)

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Reflective Cracking (S13)

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Web Performance Reports

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www.pavetrack.com

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Profiler Certification Program

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• 9.5 mm coarse granite PG67-22 mix (TSR ≈ 0.3!)

• Laboratory performance of plant produced mix– Flow number, dynamic modulus, APA– IDT, overlay tester, bond strength, PG grading– TSR, stripping via boiling, Hamburg (aged & unaged)

• Field performance on Pavement Test Track– Hot-mix control, immediate traffic (1 year thereafter)– Weekly rutting, roughness, macrotexture– Final report within 18 months of commitment

National WMA Certification Program

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Page 35: Research Findings from the NCAT Test Track APAI Winter Conference Indianapolis, December 14, 2010.

Thank Youwww.NCAT.us