Warm Mix for a Cold Climate Colorado DOT’s 2007 WMA Project.
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Transcript of Warm Mix for a Cold Climate Colorado DOT’s 2007 WMA Project.
Warm MixWarm Mix for a for a Cold Cold ClimateClimate
Colorado DOT’s2007 WMA Project
CDOT WMA BackgroundCDOT 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
CDOT WMA Site CDOT WMA Site InformationInformation
• Project Location:– I-70, 70 miles west of Denver– Mountain terrain – elev. 8,800’ to
11,100’
CDOT WMA Site CDOT WMA Site Information (2)Information (2)
• Increasing Congestion in I-70 West CorridorCritical to Industry and Tourism
CDOT WMA Project CDOT WMA Project SummarySummary
• Traffic30,000 AADT, 10% trucks, 4.85M ESALS (10-yr.)
• Extreme winter conditions (truck chain area)
CDOT WMA Project CDOT WMA Project SummarySummary
• 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
CDOT WMA Project CDOT WMA Project SummarySummary
West Portal of Eisenhower-Johnson Memorial Tunnel on I-70
WMA Job ended here and began down in Silverthorne
Project Mixture DetailsProject 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)
Project Mixture DetailsProject 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%
WMA SummaryWMA 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
WMA SummaryWMA 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.
Construction HighlightsConstruction 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
Construction HighlightsConstruction Highlights
• WMA produced at 250 °F, HMA at 280 °F – Same for lab testing temperatures
• Same roller configuration used for all 4 mixes
Advera-WMA feed system -
Similar to Sasobit feed system
- blown in like SMA fibers
Advera WMA and Sasobit blown in here
Evotherm DAT injected into AC feed line here
Same haul, placement and compaction Same haul, placement and compaction equipment used for WMA as for HMA equipment used for WMA as for HMA
sectionssections
WMA ~240°F behind the paver – no fumes
Construction HighlightsConstruction Highlights Mix Type
Property
Control 7-24-07AdveraWMA
Control 7-26-07Sasobit
Control 8-13-07Evotherm
Results are from the CDOT QA lab – QC results were comparable FHWA’s 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
MatDensity
(% 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
Hamburg Advera WMAHamburg Advera WMA
CONTROL
ADVERA
CDOT Hamburg History:75 gyration mixtures typically fail Hamburg, but fail primarily due to plastic flow rutting rather than stripping/moisture damage
Hamburg SasobitHamburg Sasobit
CONTROL
SASOBIT
Hamburg Evotherm DATHamburg Evotherm DAT
CONTROL
EVOTHERM DAT
WMA MonitoringWMA 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
ConclusionsConclusions
• 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
Questions, PleaseQuestions, Please