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