LOW TEMPERATURE
CRACKING
Dec 7, 2011
MAAPT
Tim Clyne, MnDOT
Presentation Topics





Project History
Phase I Major Findings
Phase II Research
Mixture LTC Specification
The Road Ahead
Affects Ride Quality
Median No. of Trans. Cracks per 305 m
(per 1000 ft.)
We’re Making Progress
70.0
60.0
50.0
PG XX-34 Avg.
1971 to 1980
40.0
1981 to 1990
30.0
1991 to 1994
1995 to 1999
20.0
Initial Superpave
10.0
Current spec
0.0
0
5
10
BAB Age, years
15
20
Project History
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
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
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
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 776
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
Indirect Tensile Test




Developed during SHRP program
In current MEPDG
Determines Creep Stiffness &
Tensile Strength
Test protocol AASHTO T 322-03
Creep & Strength Data
Semi Circular Bend



Apply constant Crack Mouth Opening Displacement
Determines Fracture Energy & Fracture Toughness
Proposed AASHTO Test Method
SCB Data
Disk Shaped Compact Tension



Similar to SCB except for geometry and loading rate
Determines Fracture Energy
Test protocol ASTM D 7313-06
DCT Data
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
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
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
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
20
77
500
DCT vs SCB 4% void specimens
33 21
400
800
22
PGLT
700
300
Pearson's r = 0.41
200
200
300
400
500
600
2
DCT [J/m ]
700
SCB [J/m2]
SCB [J/m2]
600
600
800
500
34
2021
400
77
33
35
300
22
Pearson's r = 0.32
200
200
300
400
500
600
2
DCT [J/m ]
700
800
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
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
Aging Plays a Role
DCT Fracture Energy
Conditioned and Field vs., Non-Conditioned
1000
900
800
Non-Conditioned
Conditioned
Field
Gf [J/m2]
700
600
500
400
300
200
100
0
20
21
22
33
34
35
77
WIS
NY
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 > 400 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
 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 (proposed fall
2011)

Extend to other types of cracking
 Fatigue,
Top Down, Reflective
Thank You!
Tim Clyne
651-366-5473
tim.clyne@state.mn.us
www.mndot.gov/mnroad