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Warm Mix for a Cold Climate

Warm Mix for a Cold Climate. Colorado DOT’s 2007 WMA Project. 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

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Warm Mix for a Cold Climate

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  1. Warm Mix for a Cold Climate Colorado DOT’s 2007 WMA Project

  2. 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’

  4. CDOT WMA Site Information (2) • Increasing Congestion in I-70 West CorridorCritical to Industry and Tourism

  5. CDOT WMA Project Summary • Traffic30,000 AADT, 10% trucks, 4.85M ESALS (10-yr.) • Extreme winter conditions (truck chain area)

  6. 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

  7. CDOT WMA Project Summary West Portal of Eisenhower-Johnson Memorial Tunnel on I-70 WMA Job ended here and began down in Silverthorne

  8. 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)

  9. Project Mixture Details • Contractor’s 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%

  10. WMA Summary • SAME mix design for WMA from HMA • CDOT spec based on NCAT’s WMA protocol • 3 additives – • Advera WMA • Sasobit • Evotherm DAT • ~1000 tons each, ~1 mile for each section

  11. 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.

  12. 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

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

  14. Advera-WMA feed system - Similar to Sasobit feed system - blown in like SMA fibers

  15. Evotherm DAT injected into AC feed line here Advera WMA and Sasobit blown in here

  16. Same haul, placement and compaction equipment used for WMA as for HMA sections WMA ~240°F behind the paver – no fumes

  17. Construction Highlights * 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

  18. Hamburg Advera WMA CDOT Hamburg History:75 gyration mixtures typically fail Hamburg, but fail primarily due to plastic flow rutting rather than stripping/moisture damage CONTROL ADVERA

  19. Hamburg Sasobit CONTROL SASOBIT

  20. Hamburg Evotherm DAT CONTROL EVOTHERM DAT

  21. 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

  22. 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

  23. Questions, Please

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