MnROAD Update Current Benefits and Future Direction
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Transcript MnROAD Update Current Benefits and Future Direction
PERFORMANCE TESTING OF
ASPHALT PAVEMENTS
SPECIFYING LOW-TEMPERATURE
CRACKING PERFORMANCE FOR
HOT-MIX ASPHALT
January 22, 2012
TRB Workshop
Tim Clyne, MnDOT
Presentation Topics
Brief Project History
Phase I Major Findings
Phase II Research
Mixture LTC Specification
The Road Ahead
Affects Ride Quality
Project History
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
Pooled Fund Project Phase I
National TAP – August 2003
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
2 Aggregate Sources
Limestone and Granite
2 Air Void Levels
Neat and Modified, PG 58-40 to 64-22
4% and 7%
2 Asphalt Contents
Optimum Design and + 0.5%
Pooled Fund Project Phase I
Field Samples
13
pavement sections around region
Experimental Modeling
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
Asphalt Binder Testing
Bending Beam Rheometer
Direct Tension
Double Edge Notched Tension
Dilatometric (Volume Change)
Phase I Major Findings
Fracture Mechanics Approach
Asphalt Mixture Testing
Binder gives a good start, but doesn’t tell whole story
Binder Grade
Modified vs. Unmodified
High temperature grade
Aggregate Type
Granite generally better than Limestone
Air Voids
Lower air voids = slightly better performance
Binder Content
More asphalt = better performance
Phase II Research
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
DCT vs. SCB
Item
DCT
SCB
Even
Equipment needed
x
Cost of test setup
x
Test time
requirement
Ease of sample
preparation
Repeatability of
results
Loading mode
Loading rate
Lab vs. Field
Ability to test thin
lifts in field
OVERALL CHOICE
x
x
x
?
?
x
x
DCT vs. SCB
DCT vs. SCB
DCT vs SCB for 4% void specimens
800
PGLT+10C
35
700
34
SCB [J/m2]
600
20
77
500
33 21
400
22
300
Pearson's r = 0.41
200
200
300
400
500
600
DCT [J/m2]
700
SCB = DCT if you remove creep!
800
Reproducibility
Reproducibilty of DCT test
1000
900
UIUC UMN
800
Gf [J/m2]
700
600
500
400
300
200
100
0
20-7-18
21-4-18
21-4-28
22-7-24
22-7-34
Equipment Cost
Item
Loading fixtures
X‐Y Tables to facilitate coring and sawing
CMOD Extensometer (Epsilon)
Temperature‐Chamber
Temperature modules and thermocouples
PC for Data Acquisition
Labview Based Interface Board
Coring barrels (qty = 5)
Labview Software for Data Acquisition
Labview Programming
Dual water cooled masonry saws
Dual saw system for flat face and notching
TOTAL
Cost
$3,000
$1,500
$1,400
$20,000
$400
$1,000
$700
$500
$1,500
$3,000
$10,000
$7,000
$50,000
Phase II Major Findings
Conditioning / Aging
None
Binder Modification
SBS
> Elvaloy > PPA
RAP
No
> Long Term Lab = Field
RAP > RAP = FRAP
Air Voids not significant
Test Temperature was significant
ILLI-TC Model
Modeling can provide:
True
performance
prediction (cracking vs.
time)
Input for maintenance
decisions
Insight for policy
decisions
LTC Specification
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 > 350 J/m2
Make adjustments if mix fails & retest
Specification Limit
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
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 (begin spring
2012)
Extend to other types of cracking
Fatigue,
Top Down, Reflective
Thank You!
Tim Clyne
651-366-5473
[email protected]
www.mndot.gov/mnroad