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Warm Mix Asphalt Warm Mix Asphalt Evaluation ProtocolEvaluation Protocol
Brian D. Prowell, P.E.Brian D. Prowell, P.E.Graham C. HurleyGraham C. Hurley
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 Benefits:Other Benefits:
–– Cool weather paving (extend season)Cool weather paving (extend season)–– Compaction aid for stiff mixesCompaction aid for stiff mixes–– Reduce bumps from preReduce bumps from pre--existing crack sealantexisting crack sealant
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 lower improve mixture workability allowing lower production and laydown temperaturesproduction and laydown temperatures–– WAM Foam WAM Foam ––KoloKolo VeidekkeVeidekke–– Zeolite Zeolite –– Eurovia/Hubbard ConstructionEurovia/Hubbard Construction–– Sasobit Sasobit –– Sasol International/Sasol AmericasSasol International/Sasol Americas–– Evotherm Evotherm –– MeadWestvacoMeadWestvaco–– Low Energy Asphalt Low Energy Asphalt -- FaircoFairco–– New Products under developmentNew Products under development
L.E.AL.E.A’’s sequential mixings 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
How does an Agency know How does an Agency know whether a new WMA whether a new WMA
additive/process or any new additive/process or any new asphalt additive will perform?asphalt additive will perform?
By using a robust evaluation By using a robust evaluation protocol based on protocol based on performance performance
testingtesting
How can a WMA product effect How can a WMA product effect performance?performance?
•• Binder propertiesBinder properties•• Mix designMix design•• Rutting performanceRutting performance•• Cracking potentialCracking potential
–– FatigueFatigue–– Low TemperatureLow Temperature
•• Moisture damageMoisture damage•• Field CompactionField Compaction
Specific ConcernsSpecific Concerns
•• Does the WMA improve field compaction Does the WMA improve field compaction (their purpose)?(their purpose)?
•• If the aging of the binder is reduced due to If the aging of the binder is reduced due to lower production temperatures, is rutting lower production temperatures, is rutting more likely?more likely?
•• If WMA improves field compaction, when If WMA improves field compaction, when does that improvement end, e.g. what does that improvement end, e.g. what happens if you dump traffic on the road at happens if you dump traffic on the road at 6:00 AM while it is still hot?6:00 AM while it is still hot?
Specific Concerns (Continued)Specific Concerns (Continued)
•• Is moisture damage more likely if the Is moisture damage more likely if the aggregates are not completely dry due aggregates are not completely dry due to lower temperatures?to lower temperatures?
•• Will a wax additive increase the Will a wax additive increase the likelihood for low temperature cracking?likelihood for low temperature cracking?
•• Is mixture stiffness (modulus) reduced Is mixture stiffness (modulus) reduced by decreased aging of the binder?by decreased aging of the binder?
NCAT, with the assistance of Dr. NCAT, with the assistance of Dr. Mary StroupMary Stroup--Gardiner from AU, Gardiner from AU,
developed an evaluation protocol developed an evaluation protocol to address these questionsto address these questions
A separate standardized field data A separate standardized field data collection/evaluation protocol has been collection/evaluation protocol has been
developed by the FHWA/NAPA Warm Mix developed by the FHWA/NAPA Warm Mix Asphalt TWGAsphalt TWG
Evaluate Potential for Low Evaluate Potential for Low Temperature CrackingTemperature Cracking
•• Low temperature cracking potential is primarily Low temperature cracking potential is primarily related to the binder propertiesrelated to the binder properties
•• Used AASHTO MPUsed AASHTO MP--1A to evaluate low temperature 1A to evaluate low temperature cracking potentialcracking potential
•• Probably overly conservative if product used to Probably overly conservative if product used to reduce production temperaturesreduce production temperatures
•• Lower production temperature Lower production temperature --> reduced aging of > reduced aging of the binder the binder --> reduced stiffness for some period of > reduced stiffness for some period of timetime
•• Superpave IDT test included in field evaluation Superpave IDT test included in field evaluation protocol on reheated materialprotocol on reheated material
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
Evaluate Effect on Mix DesignEvaluate Effect on Mix Design
•• Chose a virgin mix design with a granite Chose a virgin mix design with a granite aggregate used by a contractor supplying one aggregate used by a contractor supplying one of the additivesof the additives–– Original mix design was Ndesign = 125Original mix design was Ndesign = 125–– Coarse gradedCoarse graded
•• Replicated mix design with limestone Replicated mix design with limestone aggregateaggregate
•• Aged and compacted samples at 190, 230, Aged and compacted samples at 190, 230, 265 and 300265 and 300°°F, samples mixed 35F, samples mixed 35°°F higher F higher temperaturetemperature
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
Measuring Field Measuring Field CompactabilityCompactability
•• Not SGC Not SGC –– Constant shear deviceConstant shear device•• Constant stress device better simulates a Constant stress device better simulates a
roller in the fieldroller in the field–– Rolling wheel compactorRolling wheel compactor–– PTI vibratory compactorPTI vibratory compactor
•• NCAT used vibratory compactor since we did NCAT used vibratory compactor since we did not have a rolling wheelnot have a rolling wheel
•• Used vibratory compactor to produce Used vibratory compactor to produce performance specimens since density effects performance specimens since density effects performanceperformance
ModulusModulus•• Stiffness of HMA input for MStiffness of HMA input for M--E pavement E pavement
designdesign•• Dynamic modulusDynamic modulus
–– Recommended for field evaluation protocolRecommended for field evaluation protocol–– Preparing samples in field without reheating can Preparing samples in field without reheating can
be hit or missbe hit or miss•• Resilient modulusResilient modulus
–– DiametralDiametral test used in test used in NCATNCAT’’ss laboratory laboratory evaluationsevaluations
–– Testing variability can mask differencesTesting variability can mask differences
Test Samples for SPT TestsTest Samples for SPT Tests
150 mm tall by 100 mm diameter, cored from SGC
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
Rutting SusceptibilityRutting Susceptibility
•• Simple Performance TestSimple Performance Test–– Repeated load permanent deformationRepeated load permanent deformation–– Field protocol recommends testing at Field protocol recommends testing at
climatic high temperature climatic high temperature -- 66°°, e.g. 64 , e.g. 64 –– 6 = 6 = 5858°°C and 600 C and 600 kPakPa
•• Torture TestTorture Test–– Asphalt Pavement Analyzer at climatic high Asphalt Pavement Analyzer at climatic high
temperaturetemperature–– Hamburg TestHamburg Test
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
Strength GainStrength Gain•• WMA materials improve compactionWMA materials improve compaction•• What happens, if anything, if you open What happens, if anything, if you open
roadway to traffic while WMA is still hot?roadway to traffic while WMA is still hot?•• Basically looking at a change in binder Basically looking at a change in binder
properties with timeproperties with time•• For example, true emulsion mixes will For example, true emulsion mixes will ““curecure””
to a higher strengthto a higher strength•• Indirect tensile strength sensitive to binder Indirect tensile strength sensitive to binder
stiffnessstiffness
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
Moisture SusceptibilityMoisture Susceptibility
•• Laboratory moisture susceptibility tests Laboratory moisture susceptibility tests typically performed on oven dry aggregatestypically performed on oven dry aggregates
•• Lower production temperatures used in WMA Lower production temperatures used in WMA may result in incomplete drying of aggregatesmay result in incomplete drying of aggregates
•• Need to simulate field conditions in laboratoryNeed to simulate field conditions in laboratory•• For field trials,For field trials, samples prepared in the samples prepared in the
field without reheatingfield without reheating
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
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
Stripping Inflection Point
Granite Hamburg Stripping Granite Hamburg Stripping Inflection PointInflection Point
AdditiveAdditiveSSD+ in SSD+ in
Bucket Mixer Bucket Mixer at 250Fat 250F
Bucket Mixer Bucket Mixer WithWith
AntiAnti--StripStrip
AntiAnti--Strip Strip AgentAgent
HMAHMA 6500*6500* NANA
8500*8500*
>10,000>10,000
NANA
0.75% LOF 0.75% LOF 65006500
ZeoliteZeolite 39753975 1.5% Lime1.5% Lime
SasobitSasobit 34503450 0.4% 0.4% MagnabondMagnabond
EvothermEvotherm >10,000>10,000 EvothermEvotherm
* One of two samples did not have striping inflection point in 10,000 cycles
Thoughts on Moisture Thoughts on Moisture SusceptibilitySusceptibility
•• Many do not Many do not ““trusttrust”” TSR testTSR test•• Hamburg is severe alternativeHamburg is severe alternative•• If mixtures pass Hamburg, they should If mixtures pass Hamburg, they should
perform in the fieldperform in the field•• Environmental conditioning system and Environmental conditioning system and
SPT for future?SPT for future?
Field SectionsField Sections
Numerous U.S. sections to dateNumerous U.S. sections to dateWorld wide in denseWorld wide in dense--grade, SMA and OGFCgrade, SMA and OGFC
Seeing is Believing!Seeing is Believing!Orlando, FL Orlando, FL -- 20042004
Hot Mix 314 F Aspha-min Mix 254 F
138.1 pcf 138.5 pcf
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
1
2
3
4
5
6
7
8
Wearing Control Wearing PG 67-22Evotherm
Wearing PG 67-22Evotherm with 3% Latex
AP
A R
ut D
epth
, mm
NCAT Test Track NCAT Test Track -- APAAPA
The Lab/Field DisconnectThe Lab/Field Disconnect
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
Elements for Field TrialsElements for Field Trials•• Samples of raw materialsSamples of raw materials•• Mix DesignMix Design
–– Aggregate propertiesAggregate properties•• TrafficTraffic•• Volumetric propertiesVolumetric properties
–– Without reheating (contractor)Without reheating (contractor)–– Reheated (agency)Reheated (agency)
•• Performance testsPerformance tests–– Rutting Rutting –– APA and SPTAPA and SPT–– E*E*–– TSR and/or HamburgTSR and/or Hamburg–– Fatigue (should be better)Fatigue (should be better)–– Low Temperature IDTLow Temperature IDT
•• InIn--place densityplace density–– Bond strengthBond strength–– Change in density with timeChange in density with time
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
Burner Fuel?
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
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?
The Bottom LineThe Bottom Line
What ever we add to HMA or however What ever we add to HMA or however we decide to make HMA differently, we we decide to make HMA differently, we need a means to evaluate the change need a means to evaluate the change to ensure that it will give us equal or to ensure that it will give us equal or
better performancebetter performance
Performance Tests: WhatPerformance Tests: What’’s s Needed (Circa 2004)Needed (Circa 2004)
•• Accurate and precise performance tests Accurate and precise performance tests we are confident inwe are confident in
•• Timely resultsTimely results•• User friendlyUser friendly•• Relationship between the test results Relationship between the test results
and field performanceand field performance•• Relationship between reduced field Relationship between reduced field
performance and costperformance and cost
For More Information:www.ncat.usNCAT 05-04 Aspha-minNCAT 05-06 SasobitNCAT 06-02 Evotherm