hma - the sustainable pavement choice - apam, asphalt pavement
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HMA HMA -- The Sustainable The Sustainable
Pavement ChoicePavement ChoiceCharles E. Mills, P.E.Charles E. Mills, P.E.
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What is Sustainability? What is Sustainability?
““Meeting the needs of Meeting the needs of the present without the present without compromising the compromising the ability of future ability of future generations to meet generations to meet their own needs.their own needs.”” Social contextSocial context
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Sustainable PavementSustainable Pavement
• Perpetual asphalt pavements Require less energy to construct
• Per ASCE…20% less• Less energy consumed by public• Less maintenance keeps traffic
moving
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Why is Asphalt SustainableWhy is Asphalt Sustainable
• 100% Recyclable• Can use other recycled materials• Low carbon footprint pavement• Long life & fast resurfacing• Warm-Mix Asphalt• Porous pavement for stormwater
management
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
How Does Asphalt Measure Up?How Does Asphalt Measure Up?
•• EnvironmentEnvironment–– Carbon footprintCarbon footprint–– Impact Impact
•• RecyclingRecycling•• Perpetual pavementsPerpetual pavements•• LEEDLEEDTMTM
–– Porous pavementsPorous pavements–– Urban heat islandUrban heat island
•• SummarySummary
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
HMA and the EnvironmentHMA and the Environment
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What Emissions can be What Emissions can be Produced at an HMA Plant?Produced at an HMA Plant?
• Mainly products of combustion from burning No. 2 oil, natural gas, or similar fuels to heat the aggregate, similar to that produced from your home oil or natural gas furnace or an automobile
• Dust• Steam
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
HMA Plant EmissionsHMA Plant Emissions
• As part of the Clean Air Act, the U.S. Environmental Protection Agency maintains a list of categories of major sources of Hazardous Air Pollutant (HAP) emissions
• The U.S. EPA does not include HMA plants on this list
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Ways to Reduce EmissionsWays to Reduce Emissions
• Sustainable Pavements• Warm Mix• RAP• Plant O & M• Truck and other equipment
maintenance
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Global Warming and Carbon FootprintGlobal Warming and Carbon Footprint
• Greenhouse gases, such as CO2
, have been linked with global warming
• CO2
is a byproduct of combustion• Carbon footprint describes all of the
greenhouse gases caused directly or indirectly by a given process or product
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
C/o National Academy of Science
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What is a Greenhouse Gas?What is a Greenhouse Gas?
• Gases that trap heat in the atmosphere –
Allows us to live
here• Some occur from nature, others
from anthropogenic activities
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What is a Greenhouse Gas?What is a Greenhouse Gas?
Principal greenhouse gases entering the atmosphere from human activities are:
• Carbon dioxide (CO2)• Methane (CH4)• Nitrous Oxides (N2O)• Fluorinated gases (HFCs
& PFCs)
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What the heck is a Carbon What the heck is a Carbon Footprint?Footprint?
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
A carbon footprint is defined as:A carbon footprint is defined as:
The total amount of greenhouse gases produced to directly and
indirectly support human activities, usually expressed in equivalent tons
of (CO2)
Environmental SustainabilityEnvironmental Sustainability
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Studies to Compare HMA and Studies to Compare HMA and Hydraulic Cement Concrete Hydraulic Cement Concrete
Pavements Energy UsePavements Energy Use•• Horvath and Hendrickson, 1998Horvath and Hendrickson, 1998
–– Economic input/output based lifeEconomic input/output based life--cycle cycle analysisanalysis
–– 11.8 in. HMA vs. 8.7 in. CRCP11.8 in. HMA vs. 8.7 in. CRCP–– Estimated that it takes approximately Estimated that it takes approximately ½½ the the
energy to produce a mile of HMA vs. a mile energy to produce a mile of HMA vs. a mile of CRCP pavement (0.93 million vs. 1.85 of CRCP pavement (0.93 million vs. 1.85 million kW hr.) million kW hr.)
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Energy Use by Road Material TypeEnergy Use by Road Material Type
126 142 149178 182 189 205
341
0
50
100
150
200
250
300
350
400
HMA 50%RAP
HMA 30%RAP
HMA 20%RAP
HMA 10%RAP
Warm Mix Hot-Mix ConcretePavement
ReinforcedConcretePavement
kW*h
/ton
Colas Group DataColas Group Data
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
U.S. EPA LifeU.S. EPA Life--Cycle ApproachCycle Approach•• U.S. EPA lifeU.S. EPA life--cycle approach tracks flows cycle approach tracks flows
upstreamupstream•• Sources of greenhouse gases included with Sources of greenhouse gases included with
an HMA pavement include:an HMA pavement include:–– Extraction and processing of aggregate at quarryExtraction and processing of aggregate at quarry–– Extraction of oil and refining of asphaltExtraction of oil and refining of asphalt–– Transportation of raw materialsTransportation of raw materials–– Production of HMA (heating and drying Production of HMA (heating and drying
aggregates; mixing with asphalt)aggregates; mixing with asphalt)–– Transportation to paving siteTransportation to paving site–– Placement and compactionPlacement and compaction
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Studies to Compare HMA and Studies to Compare HMA and Hydraulic Cement Concrete Hydraulic Cement Concrete
PavementsPavements
•• Swedish study (Swedish study (StrippleStripple 2001) PCC 2001) PCC pavement requires 36% more energy pavement requires 36% more energy than a comparable HMA pavementthan a comparable HMA pavement
•• Similar study using previously Similar study using previously discussed 11.8 in HMA and 8.7 in discussed 11.8 in HMA and 8.7 in CRCP sections showed HMA required CRCP sections showed HMA required 21 to 92% less energy than PCC 21 to 92% less energy than PCC ((ZappataZappata and and GambateseGambatese, 2005), 2005)
Carbon FootprintCarbon Footprint
0
2000
4000
6000
8000
10000
12000
HMA PCC PCC with 15% Fly Ash
Carbon
Dioxide
Equ
ivalen
ts, g CO
2/un
it
Use
Transportation
Manufacturing
Raw Materials
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Warm Mix AsphaltWarm Mix Asphalt
•• New technology developed in late New technology developed in late 19901990’’s which is under evaluation s which is under evaluation
•• Reduces asphalt production and lay Reduces asphalt production and lay down temperaturesdown temperatures
•• Reduced temperatures result in reduced Reduced temperatures result in reduced energy usage and reduced emissionsenergy usage and reduced emissions
•• Several technologies have been Several technologies have been developed to improve coating and developed to improve coating and workability at reduced temperaturesworkability at reduced temperatures
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
•• Present the state of Present the state of the practice for WMAthe practice for WMA–– Overview of Overview of
technologiestechnologies–– BenefitsBenefits–– Best practices for Best practices for
production and lay production and lay downdown
–– Future needsFuture needs
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Warm MixWarm Mix
• May dominate the market in < 5 years• Reduced energy consumption• Reduced emissionsEnvironmental and Occupational
• Plants compatible in congested areas• No odors
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Lower Temperature AdvantagesLower Temperature Advantages
• Lower energy consumption (≈30%)• Lower plant wear• Decreased binder aging• Early site opening –
Return to user
• Cool weather paving• Compaction aid for stiff mixes• Cooler working conditions
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
HMA and RecyclingHMA and Recycling
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Reclaimed Asphalt PavementReclaimed Asphalt Pavement (RAP)(RAP)
Recycling prevents depletion of natural Recycling prevents depletion of natural resources and reduces energy useresources and reduces energy use
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Recyclability
•• Asphalt is the No. 1 recycled materialAsphalt is the No. 1 recycled material•• 1995 FHWA Report to congress1995 FHWA Report to congress
90 Million tons reclaimed90 Million tons reclaimed
80% recycled80% recycled•• 2006 Contractor Survey2006 Contractor Survey
~69% reused in HMA~69% reused in HMA
~27% other recycling~27% other recycling
<3% discarded<3% discarded
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
020
406080
100Glass
bot
tles
Pape
rNe
wspr
int
Alum
inum
can
sSc
rap
Stee
lAs
phalt
Pvm
tPer
cent
Rec
ycle
d
FHWA / USEPA Report to Congress, EPA/600/R-93/095.
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Why Recycle RAP into HMA?
•• Best and Highest useBest and Highest use•• Reduces demand for new materialsReduces demand for new materials•• Reduces carbon footprintReduces carbon footprint•• Contains valuable materialsContains valuable materials
Aggregate ~95% >$10/tonAggregate ~95% >$10/ton
Asphalt ~5% > $600/tonAsphalt ~5% > $600/ton
Value >$39.50/ton (minus processing)Value >$39.50/ton (minus processing)
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
milling asphalt pavementmilling asphalt pavement
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
FractionationFractionation
•• RAP can be fractionated RAP can be fractionated into different sizes similar into different sizes similar to virgin stoneto virgin stone
•• Further improves Further improves consistencyconsistency
•• Finer portion contains Finer portion contains more asphaltmore asphalt
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Combining WMA and RAPCombining WMA and RAP
•• A winA win--win or Greenwin or Green--Green solution!Green solution!•• Adding 10 to 15% RAPAdding 10 to 15% RAP
– Reduces veil, increasing heat penetration, increasing bag house temperature
– Superheated virgin aggregate more likely to dry
– Lower WMA temps reduce oxidation of virgin binder –
good for RAP in terms of cracking– Aged RAP binder helps offset softer virgin
binder in terms of rutting
RAP: sustainable & carbon neutralRAP: sustainable & carbon neutralC/o Astec and NAPA
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Other Recycled Materials Used Other Recycled Materials Used in HMAin HMA
• Shingles• Crumb/Tire Rubber• Slag• Glass• Foundry Sand
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Perpetual PavementsPerpetual Pavements
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Max Tensile Strain
Pavement Foundation
High ModulusRut Resistant Material(Varies As Needed)
Flexible Fatigue ResistantMaterial 3 - 4”
1.5 - 3” SMA, OGFC or Superpave
}4”to6”
ZoneOf High
Compression
Perpetual Pavement
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
• Bottom-up Design and Construction
• Foundation
• Stable Paving Platform
• Minimize Seasonal Variability and Volume Change in Service
• Fatigue Resistant Lower Asphalt Layer
• Rut Resistant Upper Asphalt Layers
Perpetual Pavement
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
2 - 4”
Str
uct
ure
Rem
ain
s In
tact
Possible Distresses› Top-Down Fatigue
› Thermal Cracking
› Raveling
Solutions› Mill & Fill
› Thin Overlay
High Quality SMA, OGFC or Superpave
20+ YearsLater
Perpetual Pavement
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Asphalt and LEEDAsphalt and LEEDTMTM
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What is LEEDWhat is LEEDTMTM
• The U.S. Green Building Council LEED (Leadership in Energy and Environmental Design) Green Building Rating SystemTM
• Designed to encourage sustainable building and development practices
• Serves as a benchmark for the design, construction and operation of “green”
buildings
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
• USGBC LEED Program• Most popular in the nation• Preference of federal agencies• Preference of other U.S. jurisdictions• Confusing to asphalt producers• It’s only for buildings
LEEDLEEDTM TM PointsPoints
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
LEEDLEEDTMTM Rating System Rating System
CategoriesCategories
• Water efficiency• Energy and atmosphere• Materials and resources• Indoor environmental quality• Innovation in design
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
LEEDLEED--NC (New Construction)NC (New Construction)
•• Each category has certain Each category has certain prerequisites and 69 potential pointsprerequisites and 69 potential points
•• A building may be certified based on A building may be certified based on four levels of accumulated points:four levels of accumulated points:–– Certified 28Certified 28--32 points32 points–– Silver 33Silver 33--38 points38 points–– Gold 39Gold 39--51 points51 points–– Platinum 52Platinum 52--60 points60 points
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
LEEDLEEDTMTM Score Card for AsphaltScore Card for Asphalt
Rating Category
Credit Description PointsLEED-NC1 LEED-
Schools2LEED- Retail3
Sustainable SitesSS Credit 6.1 Storm Water Design: Quantity
Control1 1 1
SS Credit 6.2 Storm Water Design: Quality Control
1 1 1
SS Credit 7.X Heat Island Effect: Non-Roof 1 for 50% 1 for 50% 1 for 25%2 for 50%3 for 75%
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
LEEDLEEDTMTM Score Card for AsphaltScore Card for Asphalt
Rating Category
Credit Description PointsLEED-NC1 LEED-
Schools2LEED- Retail3
Materials and ResourcesMR 2.X Construction Waste
Management: Divert from Disposal
1 for 50%2 for 75%
1 for 50%2 for 75%
1 for 50%2 for 75%
MR 3.X Materials Reuse 1 for 10%2 for 20%
1 for 10%2 for 20%
1 for 10%2 for 20%
MR 4.X Recycled Content: (post consumer ½ pre-consumer)
1 for 10%2 for 20%
1 for 10%2 for 20%
1 for 10%2 for 20%
MR Credit 5.X Regional Materials: Extracted, processed, and manufactured Regionally
1 for 10%2 for 20%
1 for 10%2 for 20%
1 for 10%2 for 20%
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
LEEDLEEDTMTM Score Card for AsphaltScore Card for Asphalt
Rating Category
Credit Description PointsLEED-NC1 LEED-
Schools2LEED- Retail3
Innovation and Design ProcessID 1.X Exceptional Performance
Exceeding Expectations or Areas Not Addressed
1 to 4 1 to 4 1 to 4
Total Possible Points 69 79 70Possible Contribution4 13 13 15Minimum Required for Certification 26-32 29-36 26-32
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Porous PavementsPorous Pavements
Reduce storm water quantity and Reduce storm water quantity and improves water qualityimproves water quality
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Porous asphalt Pavements• Conserves water • Allows for better use of
land • Reduces runoff • Promotes infiltration • Cleans stormwater• Replenishes aquifers • Protects streams
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
What are Porous Pavements?
Open-Graded HMA ~ 2 ½”
½”
Agg. (#57) ~ 1 –
2”
Thick
Clean Uniformly Graded 2”-3”Crushed Agg. (#2) –
40% Voids
Non-Woven Geotextile
Uncompacted Subgrade
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Porous asphalt Pavements
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Porous asphalt Pavements
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Porous asphalt Pavements
Porous HMAConventional HMA
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Water Quality
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Walden Pond 1977Walden Pond 19771997 Report: “Twenty years later, a long time for one paving job on
that busy parking lot, it still looks good and works well.”
2008
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
porous streets !porous streets !
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
porous streets !!porous streets !!
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
LEEDLEEDTMTM Score Card for AsphaltScore Card for Asphalt
Rating Category
Credit Description PointsLEED-NC1 LEED-
Schools2LEED- Retail3
Sustainable SitesSS Credit 6.1 Storm Water Design: Quantity
Control1 1 1
SS Credit 6.2 Storm Water Design: Quality Control
1 1 1
SS Credit 7.X Heat Island Effect: Non-Roof 1 for 50% 1 for 50% 1 for 25%2 for 50%3 for 75%
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
SS Credit 6.2 SS Credit 6.2 –– Runoff QualityRunoff Quality
•• Must remove 80% of total suspended solids from 90% Must remove 80% of total suspended solids from 90% of rainfallof rainfall
•• Pavement surfaces can collect contaminants like oil, Pavement surfaces can collect contaminants like oil, grease, and salt, which can end up in pavement runoff grease, and salt, which can end up in pavement runoff
•• Pollutants, particularly suspended solids, can be Pollutants, particularly suspended solids, can be filtered out as the runoff passes through the pores of filtered out as the runoff passes through the pores of the porous asphalt the porous asphalt
•• A recent study conducted for Texas Department of A recent study conducted for Texas Department of Transportation (TXDOT) indicated porous asphalt Transportation (TXDOT) indicated porous asphalt produced a 91 percent reduction in total suspended produced a 91 percent reduction in total suspended solids (TSS) over a 21solids (TSS) over a 21--month sampling periodmonth sampling period
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Urban Heat Island EffectUrban Heat Island Effect
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Urban Heat IslandsUrban Heat Islands
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Urban Heat IslandsUrban Heat Islands
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Urban heat island effect Urban heat island effect is notis not a a
cause of Global Warmingcause of Global Warming
U.S. EPA argues it indirectly U.S. EPA argues it indirectly contributes due to increased air contributes due to increased air
conditioning useconditioning use
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
myth or reality ?myth or reality ?
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
reflectivity & temperaturesreflectivity & temperatures
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Solar Reflectance Index (Solar Reflectance Index (AlbedoAlbedo))
• Testing by Lawrence-Livermore National Laboratories has related Albedo
to pavement temperature
• LEEDTM
requires solar reflectance
index > 0.29 for credit SS 7.XX for > 50% of hardscape
• Solar reflectance of asphalt increases 200% over first five-years to a mean value of 0.12
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
0
5
10
15
20
25
30
35
40
New Old (~ 7 years)
Pavement Surface
SRI (
%)
HMA PCC
Tran et al., TRB 2009
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
Improving Solar Reflectance of Improving Solar Reflectance of AsphaltAsphalt
• The solar reflectance index of asphalt pavements increases with age,
• Light colored aggregates increase solar reflectance,
• Synthetic binders can be any color,• Durable surface coatings can be applied
to the asphalt surface, • Resin modified pavement, or• Porous asphalt.
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
SummarySummary
• HMA uses less energy and produces less greenhouse gases on a life-cycle basis than PCC– New technologies further reducing emissions
• Recycling HMA (RAP) saves natural resources– Synthetic, plant based binders, offer truly
sustainable concept for future
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
SummarySummary
•• Perpetual pavements = long life = reduced Perpetual pavements = long life = reduced material consumption and energy usematerial consumption and energy use
•• LEEDLEEDTMTM
–– Porous pavements reduce runoff, increase Porous pavements reduce runoff, increase infiltration and improve water qualityinfiltration and improve water quality
–– Urban heat island not a Urban heat island not a ““black or whiteblack or white”” issueissue
–– Many techniques available to improve solar Many techniques available to improve solar reflectancereflectance
HMA – The Sustainable Choice SMOOTH | DURABLE | SAFE | QUIET
HMA HMA -- The Sustainable The Sustainable
Pavement ChoicePavement Choice