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

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 4 th cycle

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5 5 Lab Testing

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

Benefits of OGFC: safety, noise, smoothness Lowering N design 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

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

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

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Track Layout 11

2009 Thinner Structural Test Sections 12

13 Perpetual Pavement on Soft Clay N8 Strain = e *Temperature R 2 = 0.96 N9 Strain = e *Temperature R 2 = Mid-Depth Temperature, F Tensile Microstrain N8N9 10” 14”

14 Perpetual Pavement on Soft Clay Visible Cracks on Pavement Surface Cracks appear on surface

15 Perpetual Pavement on Soft Clay 14” pavement looks great after 16.2 million ESALs 10” pavement recently rehabilitated for 2 nd time – In need of 1 st 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

Perpetual Pavements 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

17 Layer Coefficient Recalibration 18.5% Thinner

Layer Coefficient Recalibration 18 Technology has improved since AASHO Road Test Need to recalibrate coefficients Increase a 1 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

Group Experiment (+)

Group Experiment (+)

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

Group Experiment – High RAP (N10 & N11) Control HMA Section 50% RAP Section 50% RAP WMA Section

PFC Surface Cracks (Tack Method) 23

24 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)

25 PFC Surface Permeability

26 PFC Surface Noise

27 SBS vs GTR Mill/Inlay: Rutting GTR SBS

28 Pavement Preservation (S13)

29 Temperature Reduction (S13)

30 Reflective Cracking (S13)

Web Performance Reports 31

Profiler Certification Program 33

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 34

Thank You