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Project Update SD2008-03 Evaluation of Warm Mix Asphalt Concrete
Pavement in South Dakota Conditions
John FosterSDDOT Office of Research
Pierre, SD
PI-Peter Sebaaly, University of Nevada-Reno
Connecting South Dakota and the Nation
2012 SD Asphalt ConferenceBest Western - Ramkota Pierre, SDMarch 28-29, 2012
WMA Review
WMA is a process of producing bituminous mixture for pavements at a significantly ( 50-100° F) lower temperature than conventional HMA.
Reduce temperature requirements in production from 275-325 deg. F. (HMA) to 200-275 deg. F. (WMA)
Addition or combination of additives or modifiers to lower binder viscosity, promote coating of particles at lower temps
In excess of 15 WMA technologies currently available, at least 10 in the US.– Fiber/Organic– Chemical– Physical– Foamed/Foaming Agents
Limited use in United States until 2005• Nebraska, Colorado, Wyoming 2007• Used Widely in Europe
** Reduced viscosity allows the aggregate to be fully coated at a lower temperature than what is traditionally required in HMA production.
WMA Review It’s All About Lowering the Temps…. ( 50-100° F)
– Reduced burner fuel/energy consumption– Preservation of binder properties - enhanced pavement life– Reduced emissions, odors/fumes at plant and job sites– Compliance- large metropolitan areas w/air quality restrictions
(non-attainment areas).– Improved working conditions, reduced hazards to workers– Improved workability– Enhanced in-place density under adverse conditions – Extend workability
• Longer haul distances• extended paving season
– More uniform mix - decreased thermal segregation– Potential for increased use of RAP
Double Barrel Green, Aquafoam, Gencor Ultrafoam GXTM
Foaming nozzles inject water into the mixing chamber~One pound of water per ton of mix
Water-Based TechnologiesProcess- Water injection at point where binder enters drum promotes asphalt foaming to coat particles
Water-Fixating Additives
2/28/2014
Advera – Hydrated Synthetic Zeolite (18-21% water)– 0.25-0.3% of mix (5 lb’s) Advera per ton of AC– Captured moisture released as steam - produces
time-release foaming of the asphalt binder – Steam droplets improve workability
Chemical Additive
EvothermEvotherm 3G (third generation) - water-free form of Evotherm can be introduced at the mix plant or asphalt terminal.
– In-line injection with the binder-- added capabilities– 5% by weight of binder recommended– Evotherm -modified binder performance matches, or may surpass
qualities of conventional HMA binder – Allows higher percentages of recycled asphalt (RAP) to be used.
2/28/2014
Warm Mix Asphalt (WMA)Topics of Special Interest to SDDOT
– Allowance for SD’s Construction Season, Materials, & Environment• More effective late season paving• Flexibility in portable plant setups…longer hauls
– Cost Savings• Burner fuel usage• Equipment fuel usage• Gained efficiencies >>increased flexibility in project planning• Potential for expanded use of RAP
– Long term benefits:• Extended pavement life• Improved Pavement Quality
– Possible Winter Season Wearing Course– Cold Weather Patching– Air Quality & Jobsite Exposure Issues
SD2008-03 Project Goals
Problem: Assess Performance Evaluate the suitability of Warm Mix Asphalt (WMA) in SD
conditions (aggregates, binders, additives, climate extremes) Assess WMA suitability in all paving applications (e.g. overlays,
leveling, interim, patching) Evaluate WMA properties (material components & mixture) Evaluate WMA pavement integrity, durability & workability
characteristics relative to HMA over time Evaluate emissions of WMA /vs. HMA during paving & production Link to thermal imaging applications (construct maps, correlate
thermal properties with other data) Cost - benefit analyses relative to the constructability,
performance, environmental factors, other considerations Link to ongoing MEPDG activities (strength/mechanistic
properties) Link to increased recycled asphalt pavement material usage
Project Review (cont)
Research Approach– Literature & Process Evaluation- Build Off of Existing Regional
Experience (Wyo.-YNP, Colorado- I 70, Nebraska – NE12)– Laboratory Designs/Protocol/Testing– Preliminary Demonstrations in 2009– Test Sections for Performance Evaluation 2010, 2011– Extended Test Section Performance Evaluations for 2
years– Emissions Testing Phase– Generate Final Report, Formulate Recommendations – Develop Implementation Plan – Duration 4/5 years– Budget: $140,000
Perspective: Approx. $150MM-$200MM invested in HMA Pavements in SD Annually
Mix Type None Advera Evotherm Foamed
LimestonePG64-28
X X X X
Quartzite PG64-28
X X X X
Nat. Gravel PG64-28
X X X X
Test Matrix
Milestones Completed WMA processes researched & evaluated, 3- technologies
selected
WMA research and literature identified & evaluated
Technical panel meetings & progress reports
Developed lab protocol & testing plan - preliminary lab results
Developed field testing evaluation protocols
Test sections constructed at three locations using three WMA technologies, side-by-side control sections
Preliminary emissions data
Laboratory Evaluation Western Regional Superpave Center
Evaluate suitability of various WMA technologies using South Dakota aggregate sources and binder types in various applications. Assess:
• optimum WMA temperatures• aggregate blend gradation • number of gyrations (for mixture classifications Q1-Q5)• binder content • verify coating • moisture sensitivity at selected design binder content • rutting resistance - Asphalt Pavement Analyzer (APA) test and the Flow
Number (FN) test.• mechanical properties - dynamic modulus |E*| is an indicator of resistance
to fatigue cracking and rutting.
Preliminary WMA Trials in 2009
Access roads and tie-in to parking lot - Turtle Creek Store, Mission, SD Nov, 2009 Mix produced by Morris plant , Pierre 100 mile haul Evotherm (0.5%) added to extend compaction window Results promising
Shoulder Reconstruction - I90 near Cactus Flats Nov, 2009 IM-0902(145)112-Shoulder Reconstruction Mix produced by Hills Materials 60 mile haul-long cycle time E mix-30% RAP PG 58-28 Terex Foaming Unit
– No production rate control of water addition-nominal setting Results - some degree of pavement failure
Hwy 73 Project
Hwy 73 Test Section
•Contractor- Border States•Cloudy, breezy, some rain, ambient ~60°F•PG64-28 binder (5.7%)•Aggregate moisture 3% - 4.4% •Standard Gyratory QA/QC protocols•HMA: 275-315°F •WMA: initially at 275°F, dropped to 250-270°F•WMA Foamed (Gencor Ultra EX) - 2500 tons
•WMA Evotherm 3G – 2400 tons•HMA control sections side-by-side •10-mile haul: 250-275°F at plant, 230-260°F front of paver, 225-255 °F behind paver•Grid layout for nuclear readings at random core locations(1000 ton sublot)•Avg. HMA fuel usage – 1.79 gal/ton < > Avg. WMA fuel usage – 1.87 gal/ton•HMA lab densities 95% < > WMA lab densities 94.5%•Consistent roller pattern (target +140°F):
• Breakdown- majority of compaction• intermediate 1% per pass •finish 0.5%
• Roller operator noted improved workability•Maintenance patching: HMA @85.1 & 87.8%, WMA 86.4%
Hwy 73 Project – Spring, 2010
Hwy 20 & Hwy 79 Projects
Hwy 20 & Hwy 79 WMA Test SectionsBison, SD
Contractor- Anderson Western Late May, 2010 Cloudy, very windy, ambients 60-70°F PG64-28 binder (5.3%) Class Q2 mix Aggregate moisture content high (?%) HMA: 275-315°F WMA: initially at 275°F, dropped to 250-270°F HMA control sections at either end and along side 0 – 40 mile haul: 275°F at plant, 260°F front of paver, 255 °F behind paver Standard gyratory QA/QC testing protocols Fuel usage – HMA -1.82 gal/ton, Evotherm WMA 1.62 gal/ton, Foamed WMA 1.72 gal/ton. Total
burner fuel savings $4800 density achieved with less effort, fewer roller passes Roller operators noted that the Evotherm WMA felt softer than the HMA and the Foam WMA. Bumps
are less sharp. Finish rolling temperatures as low as 135 (Evotherm) to140 ( Foamed). Rollers were able to remove
marks at even lower temps.
Hwy 20 & 79 – Bison, SD
Pine Ridge/Oglala - Shannon CountyHwy 18 Demonstration
Pine Ridge/Oglala - Shannon CountyHwy 18 Demonstration
Contractor- Border States Jul- late Oct, 2011 WMA- Later Oct; Cloudy, windy, cold (ambients 14-65°F) Oct 26th : 14°F at 07:30 AM, start paving at 10:30 (~32?) Some problems at startup PG64-34 binder (~5.3%) Class Q2 mix Aggregate moisture content ranged from 4%-5.5% HMA: 275-315°F WMA: 250-275°F at plant, 260°F front of paver, 255 °F behind paver HMA control sections at either end and along side 0 – 15 mile haul Standard gyratory QA/QC testing protocols Fuel usage – rough est. > HMA 1.8-2 gal/ton, WMA 1.4-1.6 gal/ton Stack testing – AET 1st experience w/Thermal Maps Results –bumpy start for Evo
Advera Injection Setup
WMA Technology
Aqua Foam Unit
Emissions Monitoring
Stack Testing:• Stack emissions during production runs• U.S. EPA stack emissions testing protocols• Certified tester (AET- Minneapolis)• 60 min test runs• HMA and WMA comparative test runs• QA/QC Program• Test for:
• NOx (Method 7E)• CO2 (Method 3A)• VOC (Method 25A)
Operating Parameters Monitored:• average production rate (tons/hr)• drag slat amperage• fuel usage• stack gas volumetric flow rates• temperature• moisture content
NOx is a generic term for the mono-nitrogen oxides NO and NO2 (nitric oxide and nitrogen dioxide). They are produced from the reaction of nitrogen and oxygen gases in the air at high temperatures. NOx eventually forms nitric acid, which contributes to acid rain.� CO2 -- carbon dioxide is one of the most significant causes of globalwarming. Asphalt binder contains carbon, which, when combusted, bonds with oxygen and forms carbon dioxide that enters the atmosphere.� VOCs are volatile organic compounds which are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, including benzene, toluene, and xylenes, some of which may have short and long-term adverse health effects.
Run 1 Run 2 Run 3 Average
HMA Emissions (PG64-22, Production Temp = 290F) – Tuesday, Oct. 18th 2011NOx( lbs./hr) 11.6 10.7 11.0 11.1 CO2 ( lbs./hr) 11,928 12,692 12,554 12,391
VOC (lbs./hr) as propane 55.4 109.7 62.3 75.8 WMA-Advera Emissions (PG64-34, Production Temp = 260F) – Wednesday, Oct. 19th 2011
NOx( lbs./hr) 11.3 11.0 11.6 11.3 CO2 ( lbs./hr) 11,986 10,349 11,051 11,129
VOC (lbs./hr) as propane 71.8 57.7 57.3 62.3 WMA-Advera Emissions (PG64-34, Production Temp = 270F) – Thursday, Oct. 20th 2011
NOx( lbs./hr) 14.1 10.8 9.5 11.5 CO2 ( lbs./hr) 11,985 12,260 12,056 12,100
VOC (lbs./hr) as propane 70.1 63.8 71.2 68.4
• NOx levels fairly equivalent for HMA & WMA • Decrease in measured CO2 and VOC observed with
decrease in production temperatureTest Results
Stack Emissions
Job Site Emissions - plan
Quantify asphalt fume emissions in vicinity of paver – Traditional gravimetric procedures (NIOSH Method 5042) Airborne total particulate (TP) material and benzene-soluble fraction (BSF) Clip-on monitors Monitor atmospheric conditions - wind speed/direction, air temp, humidity
Impact on Emissions
EmissionPercent Reductions relative to HMA
Norway Italy Netherlands France Canada SD∆T=30º F
Carbon dioxide: CO2 31.5 30-40 15-30 23.0 45.8 18
Sulfur dioxide: SO2 NA 5.0 NA 18.0 41.2 NA
Volatile organic compounds: VOC NA 50.0 NA 19.0 NA 47%
Carbon monoxide: CO 28.5 10-30 NA NA 63.1 NA
Oxides of nitrogen: NOx 62.5 60-70 NA 18.0* 58.0 0
Dust 54.0 25-55 NA NA NA NA2/28/2014
WMA Hwy 18 – Pavement Density Check
Station Lane Point Offset Density Gauge UW
Est. Density (%)
250+00 EB 1.5 ft. Right 148.6 96.4
“” “” 6.5 ft. Right 147.9 96.0
“” “” 12.5 ft. Right
147.0 95.4
205+00* EB 1.5 ft. Right 144.7 93.9
“” “” 6.5 ft. Right 147.9 96.0
“” “” 12.5 ft. Right
146.4 95.0
204+00* EB 12.5 ft. Right
147.4 95.6
203+00* EB 12.5 ft. Right
147.5 95.7
Evotherm
MOBA Pave IREstablished relationship between thermal signature and density
Mapping of Thermal Profiles • Easy to retrofit • User friendly• Built rugged for mobile applications• Can retrofit to any screed
Data from US 18 Ogallala-Pine Ridge Border States Paving: 10/23/2011 (Foamed WMA)
Lab Experimental Plan
12/28/2011 University of Nevada Reno, www.wrsc.unr.edu 29
Mechanical Properties Evaluated:1. Resistance of the mixtures to moisture damage
(stripping). TSR ratio2. Resistance of the mixtures to rutting APA & FN 3. Mixtures dynamic modulus (ІE*І)
Experimental Plan (PG64-28)- Process (1.5% by weight of binder) Advera (0.3% by TWM)- Evotherm 3G (0.5% by weight of binder)- Plant Foaming
12/28/2011 University of Nevada Reno, www.wrsc.unr.edu 30
* Not Tested (short on materials)
Mixture
Aggregate source Short‐Term Oven Aging Conditions
Quartzite LimestoneNatural Gravel
Volumetric Performance
HMA X X X 2hrs @ Comp. Temp 4hrs @ 275 °F
WMA‐Advera X X X 2hrs @ Comp. Temp 2hrs @ Comp. Temp
WMA‐Evotherm X X X 2hrs @ Comp. Temp 2hrs @ Comp. Temp
WMA‐Foaming X X X 2hrs @ Comp. Temp 2hrs @ Comp. Temp
HMA‐2hrs STOA X X NT* 2hrs @ Comp. Temp 2hrs @ 275 °F
HMA‐Low Temp X X X2hrs @ WMA Comp.
Temp2hrs @ WMA Comp.
Temp
Comments- Prelim. Lab Data
12/28/2011 University of Nevada Reno, www.wrsc.unr.edu 31
• Reduced mixing and compaction temperatures were achieved - up to 75°F below typical HMA production temps.
• WMA mixtures found to be workable and easy to compact compared to HMA mixtures.
• Lower production temperature and short-term conditioning had significant influence on the mixtures performance.
Resistance to Moisture Damage> WMA & HMA mixtures exhibited satisfactory moisture resistance> HMA mixtures stiffer (higher ITS) than WMA mixtures> Quartzite aggregate mixes slightly stiffer (higher ITS) than the other aggregates
12/28/2011University of Nevada Reno, www.wrsc.unr.edu32
Natural Gravel Aggregate
143
105 105 98 104
125
89 9080
93
87 85 8582
90
0
10
20
30
40
50
60
70
80
90
100
0
20
40
60
80
100
120
140
160
180
200
HMA WMA‐Advera WMA‐Evotherm WMA‐Foaming HMA‐low Temp
Tensile
Stren
gth Ra
tio at 7
7°F (25°C), %
Tensile
Stren
gth ITS at 77°F (25°C), p
si
Mixture Type
Dry ITS, psi Wet ITS, psi Tensile Strength Ratio (TSR)
Resistance to RuttingDifferent WMA mixtures exhibited acceptable rut resistance inboth APA and FN tests compared to HMA mixtures under same conditions
12/28/2011University of Nevada Reno, www.wrsc.unr.edu33
APA Test Results (AASHTO TP63)
3.91
5.14
3.96
5.92
3.57
4.29
2.32
4.16 4.21 4.03
2.45
4.36
2.56
3.28 3.27
4.41
3.43
0.0
1.0
2.0
3.0
4.0
5.0
6.0
7.0
8.0
HMA WMA‐Advera WMA‐Evotherm WMA‐Foaming HMA‐2hrs STA HMA‐low Temp
APA Ru
t Dep
th at 1
47°F (6
4C), m
m
Quartzite Lime Stone Natural Gravel
4.5 ± 0.5 % air voids.
Max. Rut depth for Q2 mix class is 7.0 mm.
Test Temperature = 64°C
12/28/2011University of Nevada Reno, www.wrsc.unr.edu34
Limestone Aggregates
1
10
100
1,000
10,000
1.E‐03 1.E‐02 1.E‐01 1.E+00 1.E+01 1.E+02 1.E+03
Dynam
ic M
odulus |E*| at 70F, ksi
Reduced Frequency, Hz
HMA Advera Evotherm Foaming HMA‐2hrs STA HMA‐Low Temp
Evotherm
HMA
stiffer
Dynamic ModulusIn general, the dynamic modulus of WMA mixes was lower (less stiff) compared to HMA mixtures, but similar or higher (more stiff) than HMA-Low Temp
WMA Activities in the Region
Similar to SD, Nebraska has full-blown research project….– SD > extended performance monitoring– SD> emissions testing
Montana, ND, Wyoming, & MN sponsoring demonstrations or already SOP
Lessons Learned…..
There seems to be no single WMA technology that is ideal in every situation…..
Selection of technology involves trade-offs…. • Foaming >>Up front capital outlay, no material costs • Evotherm >>No equipment costs, higher material cost,• Evotherm >superior performance under extremes• Foaming> utility at the cost of moderate performance
Adverse conditions >> less forgiving ….. • Better handle on project constraints - narrowed paving window, freeze-up• Logistical things (materials, haul distance, equipment, personnel)• Plant production – increased sensitivity to interruptions
Budget – increased life cycle benefit comes at a price
Yet to Be Verified….
Resistance to long-term rutting and cracking…..”jury still out”
Cost effective?…. Encouraging indications “short term” > production increases, extended
paving window, workability, increased flexibility in operations, hazards to workers, emissions, fuel savings
“long term” > aging factor,
Challenges Project selection continues to be a “dynamic’ process Operational constraints of plants
• Need to maintain temperatures• Aggregate bin freezeup• Monitoring of fuel usage
Representative samples for lab analysis (foamed)? Need for better planning/communication under adverse
conditions Emissions monitoring results > perplexing Overcoming convention – “why fix it?”
Planned 2012 Activities? Concentrate on long-term performance
monitoring, characterization of cores Convene technical panel to review project Continue data collection activities- lab/field
– More emissions testing?– Fatigue, rutting, surface profiling, etc.
Construct additional test sections??<Requirements>
– Virgin quartzite aggregate (no RAP in mix)– performance grade binder (PG64-28/PG64-34)– Q2 mix– Sufficient quantities for reasonable test
Technical Panel Bill Anderson, Pennington Co. Dave Anderson, Local Govt. Kevin Carlson, Jebro Wayne Cramer, SDDOT-Aberdeen Region Brett Hestdalen, FHWA Ryan Johnson, SDDOT-Operations Support Daris Ormesher, SDDOT-Research Rick Rowen, SDDOT-Materials & Surfacing Ken Skorseth, SDLTAP Jason Smith, SDDOT-Materials & Surfacing Ken Swedeen, DAPA
Questions?????