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PERFORMANCE TESTING OF ASPHALT PAVEMENTS SPECIFYING LOW-TEMPERATURE CRACKING PERFORMANCE FOR HOT-MIX ASPHALT Tim Clyne, MnDOT January 22, 2012 TRB Workshop.

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Presentation on theme: "PERFORMANCE TESTING OF ASPHALT PAVEMENTS SPECIFYING LOW-TEMPERATURE CRACKING PERFORMANCE FOR HOT-MIX ASPHALT Tim Clyne, MnDOT January 22, 2012 TRB Workshop."— Presentation transcript:

1 PERFORMANCE TESTING OF ASPHALT PAVEMENTS SPECIFYING LOW-TEMPERATURE CRACKING PERFORMANCE FOR HOT-MIX ASPHALT Tim Clyne, MnDOT January 22, 2012 TRB Workshop

2 Presentation Topics Brief Project History Phase I Major Findings Phase II Research Mixture LTC Specification The Road Ahead

3

4 Affects Ride Quality

5 Project History

6 Initial Studies Low Temperature Cracking of Asphalt Concrete Pavements Introduced SCB test method Developed models for crack spacing and propogation Low Temperature Cracking Performance at MnROAD Evaluated field performance of ML and LVR cells Investigation of the Low-Temperature Fracture Properties of Three MnROAD Asphalt Mixtures PG 58-28, 58-34, 58-40

7 Pooled Fund Project Phase I National TAP – August 2003

8 Pooled Fund Project Phase I Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study TPF-5(080) 16 Authors from 5 entities! Large Laboratory Experiment 10 Asphalt Binders Neat and Modified, PG 58-40 to 64-22 2 Aggregate Sources Limestone and Granite 2 Air Void Levels 4% and 7% 2 Asphalt Contents Optimum Design and + 0.5%

9 Pooled Fund Project Phase I Field Samples 13 pavement sections around region Experimental Modeling

10 Laboratory Test Procedures Indirect Tensile Test (IDT) Test protocol AASHTO T 322-03 Semi Circular Bend (SCB) Proposed AASHTO Test Disk Shaped Compact Tension ASTM D 7313-06

11 Asphalt Binder Testing Bending Beam Rheometer Direct Tension Double Edge Notched Tension Dilatometric (Volume Change)

12 Phase I Major Findings

13 Fracture Mechanics Approach

14 Asphalt Mixture Testing Binder gives a good start, but doesnt tell whole story

15 Binder Grade Modified vs. Unmodified High temperature grade

16 Aggregate Type Granite generally better than Limestone

17 Air Voids Lower air voids = slightly better performance

18 Binder Content More asphalt = better performance

19 Phase II Research

20 Objectives Develop LTC mix specification Test field additional field samples Various mix types, binder grades & modifiers, RAP Supplementary data from 12 MnROAD mixtures and 9 binders from 2008 SCB, IDT, BBR, DTT, DENT Porous, Novachip, 4.75 mm Superpave, WMA, Shingles Improved modeling capabilities

21 DCT vs. SCB ItemDCTSCBEven Equipment needed x Cost of test setup x Test time requirement x Ease of sample preparation x Repeatability of results x Loading mode ? Loading rate ? Lab vs. Fieldx Ability to test thin lifts in field x OVERALL CHOICE

22 DCT vs. SCB

23 SCB = DCT if you remove creep!

24 Reproducibility

25 Equipment Cost ItemCost Loading fixtures$3,000 X Y Tables to facilitate coring and sawing $1,500 CMOD Extensometer (Epsilon)$1,400 Temperature Chamber $20,000 Temperature modules and thermocouples$400 PC for Data Acquisition$1,000 Labview Based Interface Board$700 Coring barrels (qty = 5)$500 Labview Software for Data Acquisition$1,500 Labview Programming$3,000 Dual water cooled masonry saws$10,000 Dual saw system for flat face and notching$7,000 TOTAL$50,000

26 Phase II Major Findings Conditioning / Aging None > Long Term Lab = Field Binder Modification SBS > Elvaloy > PPA RAP No RAP > RAP = FRAP Air Voids not significant Test Temperature was significant

27 ILLI-TC Model Modeling can provide: True performance prediction (cracking vs. time) Input for maintenance decisions Insight for policy decisions

28 LTC Specification

29 Draft Mixture Specification Prepare sample during mix design Eventually perform on behind paver samples Prepare specimens at 7% air voids Long term condition per AASHTO R 30 Perform 3 replicate tests at PGLT + 10°C Average G f > 350 J/m 2 Make adjustments if mix fails & retest

30 Specification Limit

31 Possible Mixture Adjustments Binder grade Reduce Low PG (-34 vs -28) Different modifier or supplier Aggregate source Granite/taconite instead of limestone/gravel Reduce RAP/RAS content Aggregate gradation Finer gradation Increase binder content

32 Whats Next? Use pilot spec on select projects in 2012 or 2013 Implement in cooperation with Bituminous Office HMA Performance Testing project – University of Minnesota Duluth Phase I – Review of Literature & State Specifications Phase II – Lab Testing & Field Validation (begin spring 2012) Extend to other types of cracking Fatigue, Top Down, Reflective

33 Thank You! Tim Clyne 651-366-5473 tim.clyne@state.mn.us www.mndot.gov/mnroad


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