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OutlineUse of WMA in the USAWMA Benefits/ChallengesNCHRP 9-47A- WMA vs. HMA

Projects Evaluated Energy Usage, EmissionsMix DesignEngineering PropertiesShort Term Field Performance

Summary of Findings

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Warm Mix AsphaltA process or additive designed to

reduce asphalt mix production temperatures by 30 to 70°F and maintain mix workability (non-sanctioned definition)

A key part of the asphalt industry’s strategy for Sustainable Pavements

Categories: foaming, chemical and organic additives

WMA Technologies Available in U.S.

In 2005: 3In 2014: +30

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Estimated WMA ProductionNAPA Surveys

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Economics of WMAWater-Injection systems cost $30k to $80k.

Assuming $50k cost, 120,000 tons/yr., 5-year depreciation, then foamed WMA cost about 8 /tonȼ

If only 1/3 of production is WMA, then cost is 25 /tonȼ

Popular WMA additives are reported to increase cost by $2 - $3.5/ton of mix

Some costs may be offset by energy savings and other benefits

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WMA Usage

NAPA Surveys

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WMA Benefits/ChallengesBenefitsReduced energy consumptionReduced emissionsExtended haul distanceExtended construction seasonBetter work environment

ChallengesPerformance vs. HMAStandardize Mix Design

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WMA vs. HMANCHRP 9-47A

Location Route WMA Technologies Date Const.

St. Louis, MO Hall Street Evotherm ET, Sasobit, Aspha-min May-2006

Iron Mtn., MI M95 Sasobit Sep-2006

Silverthorne, CO I-70 Advera, Sasobit, Evotherm DAT Aug-2007

Franklin, TN SR45 Astec DBG, Advera, Evotherm DAT, Sasobit Oct-2007

Graham, TX US 380 Astec DBG Jun-2008

George, WA I-90 Sasobit Jun-2008

Walla Walla, WA US-12 Maxam Aquablack Apr-2010

Centreville, VA I-66 Astec DBG Jun-2010

Rapid River, MI CR-513 Evotherm 3G, and Advera Jun-2010

Baker, MT Route 322 Evotherm DAT Aug-2010

Munster, IN Calumet Ave. Evotherm, Gencor foam, Heritage wax Sep-2010

Jeff. Co., FL, SR 30 Terex foaming system Oct-2010

Queens, NY Little Neck Pkwy Cecabase, SonneWarmix, BituTech PER Oct-2010

Case Grande, AZ SR 84 Sasobit Dec-2011

NCHRP 9-47A Projects

WMA &HMA Production Temperatures

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Energy Savings with WMA

Fuel savings for WMA is proportional to the temperature reduction.

Most contractors report burner fuel usage decrease of about 10 to 15%.

Decreasing mix production temperature by 52°F resulted in an average fuel savings of 21 % (NCHRP 9-47A)

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Emissions and Worker Exposure with WMA (NCHRP 9-47A)

Stack emissions largely result of combusted fuel, reduced fuel should result in reduced CO2 emissions

A 52°F reduction in temperature (21% reduction in fuel) in in a 20% reduction in CO2 emissions

Worker exposures to respirable fumes during paving were significantly reduced

Reduction in application temperature resulted in an average 36% reduction in TOM (total organic matter)

WMA Mix DesignAppendix to AASHTO R35:Perform design with WMA additive or lab foaming deviceMixing temp. based on coating, 95% coated,

min.Compactability: SGC N92 at comp. temp. and 30°C below the comp. temp., Ratio N92 ≤ 1.25

Moisture susceptibility-AASHTO T 283, TSR ≥ 0.80

Rutting evaluation; Flow Number: AASHTO TP79, criterion depends on traffic

None of the NCHRP 9-47A field projects were designed with the Appendix to AASHTO R35

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WMA Mix Design (NCAT Recommendation NCHRP 9-47 A)

Complete volumetric mix design without the WMA technology/additive ( drop in approach) for selecting optimum asphalt contentCheck coating, compactability, moisture resistance and

rutting resistance ( if required) using laboratory produced WMA

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In Place DensitiesTSRFN

Engineering Properties HMA vs. WMA

In Place Densities (=)

After ~2 YearsAfter Construction

TSR-AASHTO M323 (= or ↓)

FN Test Results- WMA vs. HMA

Statistical Comparison9 cases FN WMA lower than HMA5 cases no statistical differences

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FN Criteria HMA&WMAIncluded in AASHTO TP 79-13

Traffic Level, Million ESALs

Minimum FN (HMA) Minimum FN (WMA)

<3 NA NA

3 to<10 50 30

10 to <30 190 105

≥30 740 415

HMA Flow Number Results

Traffic, MESALs

Min. Flow No.

<3 NA

3 to <10 50

10 to <30 190

> 30 740

Project Route Mix Heating FN

Baker, MT Route 322 Reheated 98

Rapid River, MI CR-513 Reheated 199

Casa Grande, AZ SR 84 No 61

Jefferson Co., FL SR 30No 414

Reheated 231

Queens, NY Little Neck Pkwy No 291

Munster, IN Calumet Ave. No 561

Walla Walla, WA US-12No 332

Reheated 426

Centreville, VA I-66 Reheated 1855

HMA Fn Criteria

WMA Flow Number Results

Traffic, MESALs

Min. Flow No.

<3 NA

3 to <10 30

10 to <30 105

> 30 415

Project Route Mix Heating WMA Additive FN

Baker, MT Route 322 RH Evotherm DAT 58

Rapid River, MI CR-513RH Advera 60RH Evotherm 3G 65

Casa Grande, AZ SR 84 No Sasobit 46

Jefferson Co., FL SR 30RH Terex Foam 127

No Terex Foam 157

Queens, NYLittle Neck Pkwy

No Cecabase 115

No SonneWarmix 123

No BituTech PER 128

Munster, IN Calumet Ave.

No Evotherm 3G 177

No Gencor Foam 217

No Heritage Wax 314

Walla Walla, WA US-12No Maxam Aquablack 200RH Maxam Aquablack 227

Centreville, VA I-66 RH Astec DBG 439

NCHRP 9-43 Mix Design Criteria

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Field Performance of WMA vs. HMA

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Field Performance Evaluation Procedure

Three 200-foot sections per mix Three 6” dia. cores from in right wheelpath, and

four 6” dia cores from in between wheelpathsCores used to determine the in-place density

indirect tensile strengths, specific gravity, gradation, asphalt content, and the true binder grade for each mix.

Field Performance-New ProjectsProject Mix Rutting (mm) Cracking (m)

Walla Walla, WAHMA 5 1

Maxam Aquablack 0 0

Centreville, VAHMA 3 1

Astec DBG 3 1

Rapid River, MI HMA 0 0

Evotherm 3G 0 0Advera 0 0

Baker, MT HMA 1 0

Evotherm DAT 0 0

Munster, IN

HMA 0 4Gencor Foam 0 36Evotherm 3G 0 0Heritage Wax 0 0

Jeff. Co., FL, HMA 3 0

Terex Foam 3 0

Queens, NY

HMA - 9Cecabase <1 20

SonneWarmix - 5BituTech PER - 5

Casagrande, AZHMA 3 NA

Sasobit 0 NA

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Summary Laboratory PerformanceStatistically equivalent as-constructed densities for WMA

mixes compared to the corresponding HMATSR -82% of mixes passed 0.8 minimum criterion; 6 mixes

failed: 4 WMA and 2 HMA. Since all of the field projects performed well; adjusting the TSR criterion on plant mix samples should be considered

FN results for WMA mixes lower than HMA ( 2/3 of the comparisons)

FN criteria recommended in NCHRP Report 673 for HMA and NCHRP Report 691 for WMA seem appropriate for evaluating plant produced mixes.

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Summary Short Term Field Performance

WMA and HMA had no significant difference in ruttingNo observed moisture damage in any HMA or in WMA

sectionNo apparent differences in density between HMA and WMAWMA and HMA cracking after to years- none or low severity

and extendNo significant differences in surface texture between HMA

and WMA

NCHRP Project 9-47A

NCHRP Report 779