Warm Mix for a Cold Climate

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Warm Mix for a Cold Climate

• Colorado DOTs
• 2007 WMA Project

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CDOT WMA Background

• CDOT interested in assessing WMA
• Proper compaction achieved at other WMA trials
• Concerns about moisture susceptibility of mix
• WMA test sections installed to assess performance
  in extreme mountain conditions
• Cold nighttime temperatures in our mountains
• Night Construction mandated when restricted to
  one through-lane on I-70 west

3
CDOT WMA Site Information

• Project Location
• I-70, 70 miles west of Denver
• Mountain terrain elev. 8,800 to 11,100

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CDOT WMA Site Information (2)

• Increasing Congestion in I-70 West
  CorridorCritical to Industry and Tourism

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CDOT WMA Project Summary

• Traffic30,000 AADT, 10 trucks, 4.85M ESALS
  (10-yr.)
• Extreme winter conditions (truck chain area)

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CDOT WMA Project Summary

• Climate35 annual precipitationover 200
  annual snowfall150 - 200 freeze/thaw cycles per
  year
• Cool summer conditions (construction)

July at lowest elevation on the projectWinds
avg. 8-21mph
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CDOT WMA Project Summary
West Portal of Eisenhower-Johnson Memorial Tunnel
on I-70 WMA Job ended here and began down in
Silverthorne
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Project Mixture Details

• Project scope of work
• Mill surface distress 2.5 and fill with 2.5 HMA
• Thick existing pavement
• 12 HMA over R75 fill
• Superpave dense graded mix specified
• ½-inch nominal max (Colorado SX mix)
• PG58-28 binder
• 75 gyration design
• Volumetric Acceptance for pay (Voids, VMA, AC,
  mat density, joint density)

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Project Mixture Details

• Contractors mixture design with CDOT approval
• Fine graded mix design by Everist Materials
• Production targets Voids 3.6 (/-1.2) VMA
  16.8 (/-1.2) AC 6.3 (/-0.3)
• Acceptance testing also included Stability
  TSR Min. Stability allowed 28, Min. TSR 70

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WMA Summary

• SAME mix design for WMA from HMA
• CDOT spec based on NCATs WMA protocol
• 3 additives
• Advera WMA
• Sasobit
• Evotherm DAT
• 1000 tons each, 1 mile for each section

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WMA Summary

• 3 lanes each direction
• WMA in middle lane
• WMA sections placed nearly adjacent toeach other
  to ensure similar site conditions
• Testing by QC, CDOT, FHWA
• Data collection by NCAT per WMA protocol
• production and placement equipment, weather
  conditions, compaction temps, etc.

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Construction Highlights

• WMA pre-paving meeting was critical
• final additive placement order (who goes first!)
• I.D. key personnel lots of visitors
• Safety precautions on site
• Test section paving hours each night
• Sampling/transport/testing plan
• Plant production details

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Construction Highlights

• WMA produced at 250 F, HMA at 280 F
• Same for lab testing temperatures
• Same roller configuration used for all 4 mixes

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Advera-WMA feed system - Similar to Sasobit feed
system - blown in like SMA fibers
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Evotherm DAT injected into AC feed line here
Advera WMA and Sasobit blown in here
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Same haul, placement and compaction equipment
used for WMA as for HMA sections
WMA 240F behind the paver no fumes
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Construction Highlights
Mix Type Property Control 7-24-07 Advera WMA Control 7-26-07 Sasobit Control 8-13-07 Evotherm
Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending. Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending. Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending. Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending. Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending. Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending. Results are from the CDOT QA lab QC results were comparable FHWAs mix flow number, dynamic modulus and binder test data are pending.
AC () 6.23 6.38 6.41 6.32 6.04 6.38
Voids () 3.1 1.8 3.0 2.4 3.6 2.2
VMA () 16.5 15.7 16.5 15.9 16.3 15.8
Mat Density ( Rice) 94 94 94 94 94 94
TSR () 100 83 97 111 94 80
Stability 36 34 35 36 35 34
Hamburg (mm rut) 9.46 9.79 17.31 10.49 10.10 14.86
Average of other control mix tested on the job.
Regardless of Hamburg Rut Depth, Moisture damage
more prevalent in the WMA samples than the
control samples see following pictures
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Hamburg Advera WMA
CDOT Hamburg History75 gyration mixtures
typically fail Hamburg, but fail primarily due to
plastic flow rutting rather than
stripping/moisture damage
CONTROL
ADVERA
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Hamburg Sasobit
CONTROL
SASOBIT
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Hamburg Evotherm DAT
CONTROL
EVOTHERM DAT
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WMA Monitoring

• NCAT under contract for WMA project support
• Field data collection during construction
• Long term tracking (3 years)
• Interim and final reports
• Due to harsh site conditions, we anticipate
  useful performance data within 3 years

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Conclusions

• WMA decreased voids in lab compaction
• WMA field compaction comparable at lower temps
• Hamburg moisture damage visibly more in WMA
• Early WMA performance equal to HMA on the job
• No rutting, no early distresses
• Confident that WMA facilitates cold temp.
  placement
• Will use more WMA in this corridor if performance
  is comparable to HMA

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Questions, Please