Mn/DOTOffice of Materials
A Crack is a Crack – Mn/DOT’s Perspective on Cracking in Asphalt Pavements
Tim Clyne, Roger OlsonMinnesota Department of Transportation
July 18, 2007
Presented at the Pavement Performance Prediction Symposium 2007
Laramie, Wyoming
Mn/DOTOffice of Materials
Typical Distresses in Minnesota
Transverse Cracking is Minnesota’s #1 concern
Top DownCracking
Transverse Cracking
Rutting Very little fatigue
cracking
Mn/DOTOffice of Materials
Low Temperature Cracking
• Single event• Thermal fatigue• Less severe event later in life (aging)
Mn/DOTOffice of Materials
MnROAD Mainline – When It Cracked
0
100
200
300
400
500
600
1994 1995 1996 1997 1998 1999 2000 2001 2002
Line
ar F
eet
Cell 1Cell 2Cell 3Cell 4Cell 14Cell 15Cell 16Cell 17Cell 18Cell 19Cell 20Cell 21Cell 22Cell 23
= 5 Year (PG 58-28)= 10 Year (PG 64-22)= 10 Year (PG 58-28)
February 2, 1996-39.4 F
• Cracking occurred in a 4 month period after 2/2/1996• Little increase since that time
Mn/DOTOffice of Materials
MnROAD Mainline – Where It Cracked
• Thickness had little effect on cracking• Class 6 had more cracks than Class 3 base• Driving lane had more thermal cracking than passing lane
• Traffic effects
0
100
200
300
400
500
600
700
1 2 3 4 14 15 16 17 18 19 20 21 22 23
Cra
ckin
g (F
eet)
Driving LanePassing Lane
PG 64-22
PG 58-28 PG 58-28
5 Year 10 Year
Mn/DOTOffice of Materials
Low Temperature Cracking 2-D Model
• Dave Timm et al, 2004• Coefficient of thermal contraction, Stiffness, Temperature Gradient• If Stress > Strength cracking will occur• Advanced 3-D models in current pooled fund study
Mn/DOTOffice of Materials
PG 58-28
PG 58-34 PG 58-40
PG 64-22
Mn/DOTOffice of Materials
Shoulder Cracking
• Cell 31 – cracks from shoulders propagate through lanes• PG 52-34 + RAP is common shoulder mix
Mn/DOTOffice of Materials
Reflective Cracking
• Besides LTC, Minnesota’s other main area of interest
• I-35 NB north of I-90Unbonded PCC overlayShoulder mix PG 52-34 + RAPNot a single crack since 1998
• Several sealer/rejuvenator treatments
Mn/DOTOffice of Materials
Top-Down Cracking of BOC
PCC joint traffic
Mn/DOTOffice of Materials
Transverse Cracking Percentage Comparision
100%
11%
38%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Percentage cracked
Percentage cracked after 5 years
Non-polymer modified overlay
Polymer Modified Overlay
Ultra Thin Bonded Wear Coarse
Mn/DOTOffice of Materials
Rehab of Full-Depth HMA
• Clean & Go• Route & Seal• Mill & Overlay
Milling depthSofter (PG -34) binderSTRATA, fabrics, etc.
• CIR (a little bit)• FDR (w/ & w/o stabilizer)• Whitetopping (GASP!)
Mn/DOTOffice of Materials
Saw & Seal
• Mixed results over the years
Tried it, Mn/DOT doesn’t do it anymoreSome Cities & Counties
• Cupping along every joint
Between joints OK
Mn/DOTOffice of Materials
St. Louis County Example - RAP
• PG 58-28, 30% RAPCracked to pieces
• PG 58-34, 20% RAPNo cracks
Mn/DOTOffice of Materials
Oil Gravel – “Poor Man’s Warm Asphalt”
Oil Gravel requires solid base
No Transverse Cracking or Rutting
Some Fatigue and Rough Ride
Similar to current “WMA” development
• mid to late 1990s
• MnROAD Cells 26, 27, 28, 32, Jalger Ave.
• County Highways: Blue Earth, Stearns, St. Louis
• real WMA job paved 7/11/07 in Olmsted County
Mn/DOTOffice of Materials
Shingle Research
• Manufactured WasteTH 10 near Rice5% shingles, 25% RAP, 2.2% new PG 64-28 AC30% RAP, 64-28 control section much better
• Manufactured Waste vs. Tear-Off Shingles (5% vs. 10%)
Hassan TownshipBetter performance
Mn/DOTOffice of Materials
Olmsted County Road 112
• WRI Binder Validation Study
PG 58-28 MarathonPG 58-28 CitgoPG 58-28 ValeroPG 58-34 MIF (RAP)PG 58-34 MIF (Virgin)
• Sealer/Binder study on SB lane
Mn/DOTOffice of Materials
Polyphosphoric Acid Study
• MnROAD Low Volume Road – 2007• FHWA, Innophos, MTE Services• Field validation of earlier lab work
PPA + SBS PPA + ElvaloyPPA onlySBS only
Mn/DOTOffice of Materials
Aging• Determination of Optimum Time for
Application of Surface Treatments to Asphalt Concrete Pavements (University of Minnesota)
Phase I – Literature ReviewPhase II – Lab & Field tests to predict aging
• Optimal Timing of Preventive Maintenance for Addressing Environmental Aging in HMA Pavements (new Pooled Fund project)
Understand mechanisms that cause agingApply right treatment at the right time
• Other ad hoc aging studies by Mn/DOT, U of M, Texas A&M, etc.
Mn/DOTOffice of Materials
Other Mn/DOT Efforts
• Asphalt Film ThicknessSpec is in place and being usedDo we get better performance than VMA spec?
• PG -28 vs. -34 studyDo we get better performance with modified binder? Is it cost-effective?
• LTC & RAP studies, etc.
Mn/DOTOffice of Materials
Thank You!
