low temperature cracking
DESCRIPTION
Low Temperature Cracking. Tim Clyne, MnDOT. Dec 7, 2011 MAAPT. Presentation Topics. Project History Phase I Major Findings Phase II Research Mixture LTC Specification The Road Ahead. Affects Ride Quality. We’re Making Progress. Initial Superpave. Current spec. Project History. - PowerPoint PPT PresentationTRANSCRIPT
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LOW TEMPERATURE CRACKING
Tim Clyne, MnDOTDec 7, 2011MAAPT
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Presentation Topics
Project History Phase I Major Findings Phase II Research Mixture LTC Specification The Road Ahead
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Affects Ride Quality
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We’re Making Progress
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0 5 10 15 20
Med
ian
No
. of T
ran
s. C
rack
s p
er 3
05 m
(p
er 1
000
ft.)
BAB Age, years
PG XX-34 Avg.
1971 to 1980
1981 to 1990
1991 to 1994
1995 to 1999
Current specCurrent spec
Initial SuperpaveInitial Superpave
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Project History
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Initial Project
Low Temperature Cracking of Asphalt Concrete Pavements (1999-2004)
Mihai Marasteanu, Xue Li, Timothy Clyne, Vaughan Voller, David Timm, David Newcomb
Introduced SCB test method Developed two models
Crack spacing Damage and crack propagation
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Phase I Field Performance
Low Temperature Cracking Performance at MnROAD Brief for 2007 MnROAD Lessons Learned
project Tim Clyne, Ben Worel, Mihai Marasteanu Evaluated field performance of ML and
LVR cells
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LVR Superpave Cells
Investigation of the Low-Temperature Fracture Properties of Three MnROAD Asphalt Mixtures
University of Minnesota Xinjun Li, Adam
Zofka, Xue Li, Mihai Marasteanu, Timothy R. Clyne
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Pooled Fund Project Phase I
National TAP – August 2003
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Pooled Fund Project Phase I
Investigation of Low Temperature Cracking in Asphalt Pavements National Pooled Fund Study 776
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%
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Pooled Fund Project Phase I
Field Samples 13 pavement sections around region
Experimental Modeling
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Indirect Tensile Test
Developed during SHRP program
In current MEPDG Determines Creep Stiffness &
Tensile Strength Test protocol AASHTO T 322-
03
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Creep & Strength Data
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Semi Circular Bend
Apply constant Crack Mouth Opening Displacement
Determines Fracture Energy & Fracture Toughness
Proposed AASHTO Test Method
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SCB Data
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Disk Shaped Compact Tension
Similar to SCB except for geometry and loading rate
Determines Fracture Energy Test protocol ASTM D 7313-06
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DCT Data
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Asphalt Binder Testing
Bending Beam Rheometer Direct Tension Double Edge Notched Tension Dilatometric (Volume Change)
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Phase I Major Findings
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Fracture Mechanics Approach
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Asphalt Mixture Testing
Binder gives a good start, but doesn’t tell whole story
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Binder Grade
Modified vs. Unmodified High temperature grade
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Aggregate Type
Granite generally better than Limestone
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Air Voids
Lower air voids = slightly better performance
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Binder Content
More asphalt = better performance
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Phase II Research
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Work Plan
Updated literature review Test additional field samples
Various mix types, binder grades & modifiers, RAP
Develop LTC mix specification Improved modeling capabilities Model thermal cycling effects Validate new mixture specification Final Report
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Supplementary Data
Asphalt Mixture and Binder Fracture Testing for 2008 MnROAD Construction
University of Minnesota Mihai Marasteanu, Ki Hoon Moon, Mugurel
Turos Tested 12 MnROAD mixtures and 9
binders, reported data SCB, IDT, BBR, DTT, DENT Porous, Novachip, 4.75 mm Superpave,
WMA, Shingles
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DCT vs. SCB
Item DCT SCB EvenEquipment
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. Field x Ability to test
thin lifts in field
x
OVERALL CHOICE
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DCT vs. SCB
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20
21
22
33
34
35
77
200
300
400
500
600
700
800
200 300 400 500 600 700 800
SC
B [J
/m2 ]
DCT [J/m2]
DCT vs SCB for 4% void specimens
PGLT+10C
Pearson's r = 0.41
2021
22
33
34
35
77
200
300
400
500
600
700
800
200 300 400 500 600 700 800
SC
B [J
/m2 ]
DCT [J/m2]
DCT vs SCB 4% void specimens
PGLT
Pearson's r = 0.32
DCT vs. SCB
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Equipment Cost
Item CostLoading 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
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0
100
200
300
400
500
600
700
800
900
1000
20-7-18 21-4-18 21-4-28 22-7-24 22-7-34
Gf[J
/m2 ]
Reproducibilty of DCT test
UIUC UMN
Reproducibility
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0
100
200
300
400
500
600
700
800
900
1000
20 21 22 33 34 35 77 WIS NY
Gf[J
/m2 ]
DCT Fracture Energy Conditioned and Field vs., Non-Conditioned
Non-ConditionedConditionedField
Aging Plays a Role
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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
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ILLI-TC Model
Modeling can provide: True performance
prediction (cracking vs. time)
Input for maintenance decisions
Insight for policy decisions
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LTC Specification
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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 Gf > 400 J/m2
Make adjustments if mix fails & retest
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Specification Limit
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Possible Mixture Adjustments
Binder grade Reduce Low PG (-34 vs -28) Different modifier or supplier
Aggregate source Granite/taconite instead of limestone Reduce RAP/RAS content
Aggregate gradation Finer gradation Increase binder content
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What’s 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
(proposed fall 2011) Extend to other types of cracking
Fatigue, Top Down, Reflective