Evaluation of Warm Asphalt Evaluation of Warm Asphalt TechnologiesTechnologies

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

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

While achieving the same or better density!

What is Warm Mix Asphalt?What is Warm Mix Asphalt?

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 –– MeadWestvacoMeadWestvaco–– Low Energy Asphalt Low Energy Asphalt -- FaircoFairco–– New Products under developmentNew Products under development

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

–– Aggregate coated with “soft” asphaltAggregate coated with “soft” asphalt–– 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

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 Zeolites are crystalline hydrated aluminum silicatesaluminum silicates

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

•• AsphaAspha--min is typically added at 0.3% by min is typically added at 0.3% by TWMTWM

Granulated Granulated asphaaspha--minmin®®

SasobitSasobit®®//SasoflexSasoflex

•• 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 binder or directly into mixAdded to binder or directly into mix–– 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

SasobitSasobit®®31 degree F reduction in compaction temperature

Sasobit Binder TestsSasobit Binder Tests

Test PG58-28 Base

PG64-22

Control

PG64-22 Sasobit®

PG70-22 Sasoflex

PG76-22

PG76-22 Sasoflex

Modifier None None 2.5% Sasobit® 4% Sasoflex None 4% Sasoflex

Test Temp., °C 58 64 64 70 76 76

Original DSR, G*/sin δ, kPa 1.015 1.815 1.790 2.689 1.290 1.461

RTFO DSR, G*/sin δ, kPa 2.781 3.868 3.950 4.548 3.096 2.682

Test Temp., °C 19 25 25 28 31 31

PAV DSR. G*sinδ, kPa 4138 3554 2906 2448 1059 2635

Test Temp., °C -18 -12 -12 -12 -12 -12

BBR Creep Stiffness (S), MPa

248 208 164 153 165 251

BBR m-value 0.316 0.317 0.306 0.328 0.315 0.292

SasobitSasobit®®

EvothermEvotherm®®

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

•• Chemical package provides mixing, Chemical package provides mixing, coating, workability, compaction and coating, workability, compaction and adhesion adhesion (e.g. anti(e.g. anti--stripping agents)stripping agents)

•• Some steam liberated upon mixingSome steam liberated upon mixing

L.E.A’s sequential mixingL.E.A’s sequential mixing

C o a rs e a g g r e g a te s a r e c o a te d

b y a ll th e a s p h a lt

H o t a s p h a lt

D r y , h o t c o a rs e a g g r e g a te s

M o is tu re f ro m f in e a g g re g a te s t r ig g e rs a s p h a lt fo a m in g

F o a m e d a s p h a lt e n c a p s u la te s f in e a g g re g a te s

T h e rm a l e q u ilib r iu m re a c h e dA ll a g g r e g a te s u n ifo rm e ly c o a te d

1 2 0 ° /1 5 0 °C 1 7 0 °C

1 0 0 °C

9 0 °C

P H A S E 1 P H A S E 2

P H A S E 3 P H A S E 4 P H A S E 5

Courtesy of Fairco

Product EvaluationsProduct Evaluations•• Evaluate Warm Asphalt Technologies for U.S. Paving Evaluate Warm Asphalt Technologies for U.S. Paving

PracticesPractices–– CompactionCompaction–– Quick “turnQuick “turn--over” to trafficover” to traffic–– RuttingRutting–– Resilient modulus (for pavement design)Resilient modulus (for pavement design)–– Moisture damageMoisture damage

•• Products EvaluatedProducts Evaluated–– AsphaAspha--min zeolitemin zeolite–– SasobitSasobit–– EvothermEvotherm

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

Samples mixed 35F above compaction temperature

Limestone

0

1

2

3

4

5

6

13.5 14 14.5 15 15.5 16VMA, %

Air

Voi

ds, %

Control Zeolite Sasobit Evotherm

190F

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

Air Voids Resilient Modulus APA Rutting 265 230 265 230 265 230

None = (0.8895)

= (0.1161)

= (0.9695)

= (0.9969)

= (0.3071)

< (0.0002)

Zeolite = (0.2250)

> (0.0122)

= (0.9968)

= (0.9391)

< (0.0025)

< (0.0420)

Sasobit > (0.0006)

> (0.0059)

= (1.0000)

= (0.8911)

= (0.9926)

= (0.9752)

Evotherm > (0.0000)

> (0.0001)

= (0.9801)

= (0.9987)

= (0.9833)

< (0.0087)

Comparison of Additives to Comparison of Additives to Hot Mix Produced at 300FHot Mix Produced at 300F

Moisture SusceptibilityMoisture Susceptibility

Simulating a Drum PlantSimulating a Drum Plant

Failure ModesFailure Modes

Adhesive Cohesive

Granite TSRGranite TSR

AdditiveAdditiveDry Dry

AggregateAggregate300F300F

SSD+ in SSD+ in Bucket Bucket Mixer at Mixer at

250F250F

Bucket Bucket Mixer WithMixer WithAntiAnti--StripStrip

AntiAnti--Strip Strip AgentAgent

HMAHMA 0.970.97 1.161.16 0.860.86

0.870.87

0.94*0.94*

NANA

0.75% LOF 0.75% LOF 65006500

ZeoliteZeolite 0.810.81 0.670.67 1.5% Lime1.5% Lime

SasobitSasobit 0.68 (250F)0.68 (250F) 0.710.71 0.4% 0.4% MagnabondMagnabond

EvothermEvotherm NANA 0.960.96

* Dry Strength 17.5 psi, wet strength 16.5 psi

Field SectionsField Sections

More than ten U.S. sections to dateMore than ten U.S. sections to dateWorld wide in denseWorld wide in dense--grade, SMA and OGFCgrade, SMA and OGFC

MD SMA Sasobit Trial MD SMA Sasobit Trial Capital Beltway Capital Beltway -- 20052005

OGFC with Sasobit OGFC with Sasobit Beijing, China Beijing, China -- 20052005

•Breakdown - 95°C (203°F)

•Finish - 75°C (167°F)Courtesy of Don Watson

Evotherm Test SectionsEvotherm Test SectionsNovember 2005 November 2005

E9E9N1N1N2N2

19.0 mm NMAS w/ 19.0 mm NMAS w/ Evotherm PG 67Evotherm PG 67--2222

19.0 mm NMAS w/ 19.0 mm NMAS w/ Evotherm PG 67Evotherm PG 67--2222

2”2”

2”2”

1”1”9.5 mm NMAS9.5 mm NMAS

HMA Control PG 67HMA Control PG 67--2222 Evotherm PG 67Evotherm PG 67--22 22 + 3% Latex+ 3% Latex Evotherm PG 67Evotherm PG 67--2222

NNdesigndesign = 80= 80for all mixesfor all mixes

Evotherm Wearing Course with LatexEvotherm Wearing Course with LatexMix Produced 7:00 PMMix Produced 7:00 PM Mix Loaded out 1:30 PM Mix Loaded out 1:30 PM –– next daynext day

Mix held inMix held insilo at 240Fsilo at 240Fovernightovernight

Mix Placed at 3:15 PMMix Placed at 3:15 PM Traffic Returned at 5:00 PMTraffic Returned at 5:00 PM

Evotherm Test Track Pavement DensitiesEvotherm Test Track Pavement Densities

86

88

90

92

94

96

98

Base Binder PG 67-22Surface

PG 67-22Surface w/ Latex

Den

sity

, % G

mm

Evotherm HMA

226F

311F

225F

328F

225F

205F

280-240F

Evotherm Field Rut Depths - NCAT Test Track

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

1.60

1.80

PG 67-22 Control Evotherm PG 67-22 Evotherm PG 67-22 w/ 3%Latex

Rut

Dep

th, m

m

Rut Depths after 500,000 ESALs

Missouri NMissouri Ndesigndesign VTMVTM

0

1

2

3

4

5

6

7

300 250 250 250 225 225 250 250 225 225

Compaction Temperature F

SG

C A

ir V

oids

, %

Compacted Hot Reheated

Control Sasobit Evotherm

Average of six samples

Missouri APA Rut DepthMissouri APA Rut Depth

0

1

2

3

4

5

6

7

300 250 250 250 225 225 250 250 225 225

Compaction Temperature F

APA

Rut

Dep

th, m

m

Compacted Hot Reheated

Control Sasobit Evotherm

Average of six samples

Missouri TSRMissouri TSR

Average of six samples

0.00

0.20

0.40

0.60

0.80

1.00

1.20

300 250 250 250 225 225 250 250 225 225

Compaction Temperature F

TSR

Compacted Hot Reheated

Control Sasobit Evotherm

NA

What Have We Learned?What Have We Learned?

•• WMA additives improve compaction, WMA additives improve compaction, both in the lab and in the fieldboth in the lab and in the field

•• In the lab, rutting increases with lower In the lab, rutting increases with lower temperatures temperatures –– may not translate to the may not translate to the fieldfield

•• Moisture, trapped in the aggregates and Moisture, trapped in the aggregates and introduced into the mix, still a concern. introduced into the mix, still a concern. LongLong--term affects unclear. Can mitigate term affects unclear. Can mitigate effect in lab.effect in lab.

Things We Need to Go ForwardThings We Need to Go Forward

•• Larger trials Larger trials –– Ongoing!Ongoing!•• A robust product evaluation protocol A robust product evaluation protocol –– Draft Draft

Developed!Developed!•• Better understanding of effect on rutting and Better understanding of effect on rutting and

moisture damage moisture damage –– Lab vs. FieldLab vs. Field•• Procedures for mix design and QC/QA (Do Procedures for mix design and QC/QA (Do

they need to be different?)they need to be different?)•• A way for Agencies to specifyA way for Agencies to specify

–– Temperature reduction?Temperature reduction?–– Binder grade?Binder grade?

Vision?Vision?•• Started with: Is it possible? Started with: Is it possible? –– Yes!Yes!•• Tool for the toolboxTool for the toolbox

–– Compaction aid for stiff mixesCompaction aid for stiff mixes–– Extend paving season (cold weather)Extend paving season (cold weather)–– Allow longer haul distancesAllow longer haul distances–– Address emissions and odor concerns in limited Address emissions and odor concerns in limited

urban areasurban areas

•• A future solution to changes in emissions or A future solution to changes in emissions or worker exposure requirements, worker exposure requirements, if necessaryif necessary

For More Information:www.ncat.usNCAT 05-04 Aspha-minNCAT 05-06 SasobitNCAT 06-02 Evotherm