Evaluation of Warm Asphalt Evaluation of Warm Asphalt TechnologiesTechnologies

Brian D. Prowell, P.E.Brian D. Prowell, P.E.Graham C. HurleyGraham C. Hurley

We Can Reduce Temperatures We Can Reduce Temperatures Today with No AdditivesToday with No Additives

•• PrePre--Superpave Superpave –– typical compaction typical compaction temperature 275 temperature 275 °°FF

•• Place Thicker Lifts Place Thicker Lifts –– NCHRP 9NCHRP 9--2727–– 3 x NMAS for fine graded3 x NMAS for fine graded–– 4 x NMAS for coarse graded4 x NMAS for coarse graded

•• Tarp TrucksTarp Trucks•• Drier Aggregate Drier Aggregate –– pave under stockpilespave under stockpiles

Time Available for Compaction

0

5

10

15

20

25

30

35

40

45

50

240 260 280 300 320 340Delivery Temperature, F

Tim

e, m

inut

es

1.5 in2.0 in2.5 in

Based on MultiCool

Why Warm Asphalt?Why Warm Asphalt?

Research by Stroup-Gardiner and Lange at AUIndicates increased emissions with increased temp.

Why Warm Asphalt?Why Warm Asphalt?

•• Reduce production and laydown Reduce production and laydown temperaturestemperatures

•• Reduce emissionsReduce emissions•• Reduce energy costsReduce energy costs•• Reduce aging of binderReduce aging of binder•• Other Possible Benefits:Other Possible Benefits:

–– Cool weather paving (extend season)Cool weather paving (extend season)–– Compaction aid for stiff mixesCompaction aid for stiff mixes

Comparison of Visible EmissionsComparison of Visible Emissions

311 °F 230 °F

Courtesy of Shell/Kolo Veidekke

What are Warm Asphalt What are Warm Asphalt Mixes?Mixes?

Several process have been developed to Several process have been developed to improve mixture workability allowing improve mixture workability allowing lower production and laydown lower production and laydown temperaturestemperatures–– WAM Foam WAM Foam –– Shell/Shell/KoloKolo VeidekkeVeidekke–– Zeolite Zeolite –– Eurovia/Hubbard ConstructionEurovia/Hubbard Construction–– Sasobit Sasobit –– SasolSasol Int./Moore and Int./Moore and MungerMunger–– Evotherm Evotherm -- MeadWetvacoMeadWetvaco

WAMWAM--FoamFoam•• Two Phase addition of asphaltTwo Phase addition of asphalt

–– Aggregate coated with Aggregate coated with ““softsoft”” asphaltasphalt–– Hard asphalt foamed to mix with preHard asphalt foamed to mix with pre--coated coated

aggregateaggregate–– Soft asphalt controls minimum placement Soft asphalt controls minimum placement

temperaturetemperature–– Material placed as low as 80 C (176 F), 50 Material placed as low as 80 C (176 F), 50 –– 60 C 60 C

(90 (90 –– 108 F) reduction108 F) reduction–– Requires plant modification for foaming, estimated Requires plant modification for foaming, estimated

at $50,000 at $50,000 -- $70,000. No additional costs $70,000. No additional costs thereafterthereafter

–– Special asphalt feeds may be requiredSpecial asphalt feeds may be required

bitumensoft

bitumenhard

mineral aggregates

mixer

Courtesy IFTA GmbH

Two phase bitumen mixing methodTwo phase bitumen mixing method

WAM Foam Installation in WAM Foam Installation in Hot Mix Asphalt PlantHot Mix Asphalt Plant

Courtesy of Shell/Kolo Veidekke

ZeoliteZeolite

•• Zeolites are crystalline hydrated aluminum Zeolites are crystalline hydrated aluminum silicatessilicates

•• asphaaspha--minmin®®, is a special Zeolite added to the , is a special Zeolite added to the hot mix asphalt in the temperature range of 100 hot mix asphalt in the temperature range of 100 to 200 to 200 °°C (212 to 392 C (212 to 392 °°F)F)

•• When the Zeolite is heated, it gives up its When the Zeolite is heated, it gives up its internal moisture, approximately 21% by weight, internal moisture, approximately 21% by weight, microscopically foaming the asphaltmicroscopically foaming the asphalt

Addition of Addition of asphaaspha--minmin®®

•• AsphaAspha--min is typically added at an addition min is typically added at an addition rate of 0.3% by weight of mixrate of 0.3% by weight of mix

•• Expected to increase mix cost by Expected to increase mix cost by approximately $1.50 per tonapproximately $1.50 per ton

•• Can be added to the mineral filler or fed Can be added to the mineral filler or fed separatelyseparately

•• Can be added directly into the Can be added directly into the pugmillpugmill of a of a batch plant, orbatch plant, or

•• Can be blown into a drum plant using a Can be blown into a drum plant using a specially built feederspecially built feeder

Granulated Granulated asphaaspha--minmin®®

Sasobit/SasoflexSasobit/Sasoflex

•• FischerFischer--TropschTropsch synthetic waxes synthetic waxes –– SasobitSasobit–– Produced from gasification of coal or natural gas Produced from gasification of coal or natural gas

feed stocksfeed stocks–– Added to binderAdded to binder–– Can incorporate an SBS modifier using special Can incorporate an SBS modifier using special

crosscross--linking agent (linking agent (SasoflexSasoflex))–– Does not require highDoes not require high--shear blendingshear blending–– May negatively impact low temperature propertiesMay negatively impact low temperature properties

Temperature, C

Vis

cosi

ty, c

P

Control PG 64-22 Sasobit PG 64-22

0.1

1

10

52 58 88 100 150 165 180 200

Mixing Range

Compaction Range

64 76 8270 120 135

100

500

SasobitSasobit31 degree F reduction in compaction temperature

SasobitSasobit

EvothermEvotherm

•• Emulsion Emulsion –– approximately 70% binder approximately 70% binder residueresidue

•• Includes adhesion promoters (e.g. antiIncludes adhesion promoters (e.g. anti--stripping agents)stripping agents)

•• Storage at 80 Storage at 80 °°C (176 C (176 °°F)F)•• Some steam liberated upon mixingSome steam liberated upon mixing

Project Partners (To Date)Project Partners (To Date)

NCAT

NAPA Env. Survival Fund

Eurovia/Hubbard

SasolInternational

FHWA

Mead-Westvaco

Study ObjectivesStudy Objectives

•• Evaluate Warm Asphalt Technologies Evaluate Warm Asphalt Technologies for U.S. Paving Practicesfor U.S. Paving Practices–– High productionHigh production–– Rapid TurnRapid Turn--over to trafficover to traffic

•• Potential ConcernsPotential Concerns–– ““CuringCuring”” TimeTime–– Increased Potential for Moisture DamageIncreased Potential for Moisture Damage–– Binder effectsBinder effects

Design Gradations

1.18

2.36

4.75 9.5

12.5 19

0.07

50.

15 0.3

0.6

0

10

20

30

40

50

60

70

80

90

100

Sieve Size (mm)

Perc

ent P

assi

ng

Granite

Limestone

How Do You Measure How Do You Measure Compaction in Lab? Compaction in Lab?

•• Superpave gyratory compactor is not Superpave gyratory compactor is not sensitive to reduced temperature sensitive to reduced temperature ––control mix produces the same voidscontrol mix produces the same voids

•• Field Compaction, Marshall and Field Compaction, Marshall and Vibratory (PTI) Compaction sensitive Vibratory (PTI) Compaction sensitive to temperature/workability changesto temperature/workability changes

Limestone - SGC

0.0

1.0

2.0

3.0

4.0

5.0

6.0

190 230 265 300Compaction Temperature, F

Air

Void

s, %

PG 58-28 Aspha-min PG 58-28 Control PG 64-22 Aspha-min PG 64-22 Control

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

300F 265F 230F 190F

Air

Voi

ds, %

Control Zeolite Sasobit Evotherm

Vibratory Compaction Vibratory Compaction –– GraniteGranite

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

300F 265F 230F 190F

Air

Voi

ds, %

PG 64-22 PG 64-22 2.5% Sasobit PG 70-22 4% Sasoflex PG 76-22 PG 76-22 4% Sasoflex

Vibratory Compaction Vibratory Compaction -- GraniteGranite

Summary of Laboratory Summary of Laboratory CompactionCompaction

•• AsphaAspha--min Evotherm and Sasobit min Evotherm and Sasobit improved compaction with both the SGC improved compaction with both the SGC and vibratory compactor. For PG 64and vibratory compactor. For PG 64--22:22:–– Evotherm reduced air voids Evotherm reduced air voids 1.5%1.5%–– Sasobit reduced air voids Sasobit reduced air voids 0.9%0.9%–– AsphaAspha--min reduced air voidsmin reduced air voids 0.8%0.8%

•• Warm asphalt additive may reduce design Warm asphalt additive may reduce design asphalt contentasphalt content

German Autobahn PavingGerman Autobahn Paving

Cure Time Cure Time –– Early ConcernEarly Concern

•• In Germany, traffic may not be In Germany, traffic may not be immediately returned to trafficimmediately returned to traffic

•• When does Warm asphaltWhen does Warm asphalt’’s workability s workability end?end?

•• Will pavements rut if traffic allowed on Will pavements rut if traffic allowed on an hour or so after placement?an hour or so after placement?

European Cure Time European Cure Time ExperienceExperience

•• Sasobit being used for Sasobit being used for repaving Frankfurt Airport. repaving Frankfurt Airport. –– Placing 24 inches of HMA in 7.5 Placing 24 inches of HMA in 7.5

hour window (approx. 1,500 tons)hour window (approx. 1,500 tons)–– Opening to jet aircraft at 85 C Opening to jet aircraft at 85 C

(185 F)(185 F)

•• WAM Foam Paving SMA on WAM Foam Paving SMA on ring road around Oslo Norway ring road around Oslo Norway –– Night work opened for rush Night work opened for rush hour traffichour traffic

Strength Gain ExperimentStrength Gain ExperimentZeolite Strength Gain

0

20

40

60

80

100

120

140

2 Hours 4 Hours 2 Hours +1 Day

2 Hours +3 Days

2 Hours +5 Days

Tens

ile S

tren

gth,

psi

WarmControl

Sasobit Limestone - Strength Gain

0

20

40

60

80

100

120

140

2 Hours 4 Hours 2 Hours + 1 Day 2 Hours + 3 Days 2 Hours + 5 Days

Tens

ile S

treng

th, p

si

Sasobit Control

Resilient ModulusResilient Modulus

Would the use of Warm Asphalt effect Would the use of Warm Asphalt effect pavement thickness design?pavement thickness design?

Agg

C or W

Temp

Binder

64-2

258

-28

WC 300

265

230

190

400000

320000

240000

400000

320000

240000

400000

320000

240000

AggGraniteLMS

Binder58-2864-22

C or WCW

Interaction Plot for Resilient Modulus

APA Rut TestingAPA Rut Testing

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

20.00

Control Zeolite Sasobit Evotherm

Rut

Dep

th, m

m

300F 265F 230F 190F

APA Rut Depth for PG 64APA Rut Depth for PG 64--22 22 -- GraniteGranite

Granite - APA

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

PG 64-22 PG 64-22 2.5%Sasobit

PG 70-22 4%Sasoflex

PG 76-22 PG 76-22 4%Sasoflex

Rut

Dep

th, m

m

300F 265F 230F 190F

Summary of Stiffness and Summary of Stiffness and Permanent DeformationPermanent Deformation

•• No evidence of required No evidence of required ““cure timecure time”” based on based on indirect tensile strength after various aging indirect tensile strength after various aging periodsperiods

•• Statistical Analysis indicated that the inclusion Statistical Analysis indicated that the inclusion of warm asphalt additives did not effect of warm asphalt additives did not effect modulus or APA rut depthmodulus or APA rut depth–– Decreased temperature did decrease modulus Decreased temperature did decrease modulus

and increase rut depth. This may be related to and increase rut depth. This may be related to decreased aging of the binderdecreased aging of the binder

–– Higher density generally resulted in higher Higher density generally resulted in higher modulusmodulus

Moisture SusceptibilityMoisture Susceptibility

Simulating a Drum PlantSimulating a Drum Plant

Failure ModesFailure Modes

Adhesive Cohesive

PG 64-22 Granite

0.0

2.0

4.0

6.0

8.0

10.0

12.0

14.0

16.0

18.0

20.0

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000

Cycle

Ham

burg

Rut

Dep

th, m

m

Control Sasobit

Test Terminated

Moisture SusceptibilityMoisture Susceptibility•• All technologies evaluated to date and control All technologies evaluated to date and control

have in some cases indicted moisture have in some cases indicted moisture susceptibilitysusceptibility

•• Tests at Tests at ““normalnormal”” temperatures have not temperatures have not indicted a problemindicted a problem

•• TSR and Hamburg do not always agree, TSR and Hamburg do not always agree, Hamburg sometimes indicates better Hamburg sometimes indicates better performanceperformance

•• Problems can be mitigated with antiProblems can be mitigated with anti--stripping stripping agents. agents.

Field SectionsField Sections

Laydown of Polymer Modified Laydown of Polymer Modified Warm Asphalt with Zeolite at 250 FWarm Asphalt with Zeolite at 250 F

4 passes of Rubber Tire,

followed by 4 vibratorypasses, followed by static finish roller

94% Gmm55 F Air Temp.

U.S. Drum Plant Addition of U.S. Drum Plant Addition of AsphaAspha--minmin

Seeing is Believing!Seeing is Believing!

Hot Mix 314 F Aspha-min Mix 254 F

138.1 pcf 138.5 pcf

Evotherm Field TrialEvotherm Field TrialNear Indianapolis, INNear Indianapolis, IN

July 2005July 2005

MD SMA Sasobit Trial MD SMA Sasobit Trial Capital BeltwayCapital Beltway

SummarySummary•• Three warm asphalt processes used in Three warm asphalt processes used in

Europe for up to 6 yearsEurope for up to 6 years•• Allow compaction at lower temperaturesAllow compaction at lower temperatures•• SGC not sensitive to compaction temperatureSGC not sensitive to compaction temperature•• Data indicates warm asphalt additive could Data indicates warm asphalt additive could

reduce optimum asphalt contentreduce optimum asphalt content•• Minimum temperature to which compaction is Minimum temperature to which compaction is

improved is dependent upon technology improved is dependent upon technology ––ranges from 265 to less than 190 ranges from 265 to less than 190 °°FF

SummarySummary•• Rutting susceptibility of warm asphalt mixtures similar Rutting susceptibility of warm asphalt mixtures similar

to hot mix produced at the same temperatureto hot mix produced at the same temperature–– Some technologies improve rutting susceptibilitySome technologies improve rutting susceptibility–– Rutting tends to increase with reduced production Rutting tends to increase with reduced production

temperatures due to decreased aging of the bindertemperatures due to decreased aging of the binder–– May need to use a stiffer binder below mixing temperatures May need to use a stiffer binder below mixing temperatures

of 275 of 275 °°FF•• Lower production temperatures may increase Lower production temperatures may increase

potential for moisture damage due to incomplete potential for moisture damage due to incomplete drying of the aggregatedrying of the aggregate–– Certain technologies may increase moisture susceptibilityCertain technologies may increase moisture susceptibility–– Moisture susceptibility can be mitigated with appropriate Moisture susceptibility can be mitigated with appropriate

additivesadditives

RecommendationsRecommendations

•• At this time, determine optimum asphalt At this time, determine optimum asphalt content content withoutwithout warm asphalt additivewarm asphalt additive

•• If mixing temperature is below 275 If mixing temperature is below 275 °°F, F, consider using stiffer binder gradeconsider using stiffer binder grade

•• Conduct Tensile Strength Ratio Tests at Conduct Tensile Strength Ratio Tests at anticipated production temperaturesanticipated production temperatures

•• Consider use of Hamburg wheel Consider use of Hamburg wheel tracking test in lieu of TSRtracking test in lieu of TSR

A Word About CostA Word About Cost•• Most additives, warm asphalt or other, are Most additives, warm asphalt or other, are

expected to increase the price of the HMAexpected to increase the price of the HMA•• Some processes or additives may require Some processes or additives may require

plant/production modificationsplant/production modifications•• It is not anticipated that the fuel savings will It is not anticipated that the fuel savings will

totally offset these coststotally offset these costs•• This project is a look ahead to make sure that This project is a look ahead to make sure that

we can continue paving, even in nonwe can continue paving, even in non--attainment areasattainment areas