hma - the sustainable pavement choice - apam, asphalt pavement

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


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


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


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 and the EnvironmentHMA and the Environment


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 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


Ways to Reduce EmissionsWays to Reduce Emissions

• Sustainable Pavements• Warm Mix• RAP• Plant O & M• Truck and other equipment

maintenance

Presenter

Presentation Notes

Sustainable Pavements – Perpetual Pavements, Porous Pavements and Pavements using RAP.


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


C/o National Academy of Science


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

Presenter

Presentation Notes

Anthropogenic effects, processes or materials are those that are derived from human activities, as opposed to those occurring in natural environments without human influence.


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)


What the heck is a Carbon What the heck is a Carbon Footprint?Footprint?


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


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.)


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


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


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)

Presenter

Presentation Notes

The BEES (Building for Environmental and Economic Sustainability) software brings to your fingertips a powerful technique for selecting cost-effective, environmentally-preferable building products. Developed by the NIST (National Institute of Standards and Technology) Building and Fire Research Laboratory. BEES measures the environmental performance of building products by using the life-cycle assessment approach specified in the ISO 14040 series of standards. All stages in the life of a product are analyzed: raw material acquisition, manufacture, transportation, installation, use, and recycling and waste management.

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


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


•• 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


Warm MixWarm Mix

• May dominate the market in < 5 years• Reduced energy consumption• Reduced emissionsEnvironmental and Occupational

• Plants compatible in congested areas• No odors


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 and RecyclingHMA and Recycling


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


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


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.

Presenter

Presentation Notes

Asphalt pavement is the most recycled material by percentage and total amount


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)


milling asphalt pavementmilling asphalt pavement


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


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


Other Recycled Materials Used Other Recycled Materials Used in HMAin HMA

• Shingles• Crumb/Tire Rubber• Slag• Glass• Foundry Sand


Perpetual PavementsPerpetual Pavements


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

Presenter

Presentation Notes

This is the concept underlying the perpetual pavement. Traffic stresses are highest near the surface of the pavement, so materials in the upper pavement layers must be resistant to rutting. The intermediate or binder courses should be comprised of rut-resistant material. Materials which have worked well include large-stone mixtures or others which provide a strong stone skeleton. Fatigue resistance is important in the lowest HMA layer or base layer. It is well documented that the most costly form of distress to fix in a pavement is bottom-up fatigue cracking. The pavement foundation serves as the ultimate support for the structure during construction and service, so it must be considered an integral part of the pavement.


• 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

Presenter

Presentation Notes

Bottom-up design and construction is a recognition that all the layers act in concert to determine the useful life and failure mode of a pavement. So, the pavement is treated as an interacting system. The foundation serves two very important purposes. First, it serves as a stable construction platform to support trucks, pavers and rollers, as well as providing resistance for proper compaction. Then, it must be resistant to volume change and seasonal variability during service so that weaknesses in the soil do not affect the long-term pavement performance. Fatigue resistance in the lower layer can be approached by designing the HMA to be more flexible or by ensuring that the total HMA thickness is such that bottom-up fatigue cracking does not occur. Rutting resistance in the upper pavement layers can be obtained using established practices. Materials selection and mix design must recognize the need for shear resistance in this zone of the structure. The surface may be either a stone matrix asphalt (SMA), open-graded friction course (OGFC) or a high-quality Superpave mixture.


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

Presenter

Presentation Notes

What makes the Perpetual Pavement perpetual is that, while the surface will need periodic replacement, the bulk of the pavement structure will remain intact. Depending on the type of surface material used and the environmental conditions present, the types of distress which may arise could include top-down fatigue cracking, thermal cracking and raveling.(Click mouse to activate animated cracks.) Although surface layer lives may vary, current technology allows for achieving over 20 years, if so desired. Solutions for these distresses could include milling off the old layer and replacing it with a new surface (Click to show overlay) or simply overlaying the pavement. One advantage to this approach is that new innovations in technology can be applied to the pavement surface as they become available, possibly further extending the surface life.


Asphalt and LEEDAsphalt and LEEDTMTM


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


• 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


LEEDLEEDTMTM Rating System Rating System

CategoriesCategories

• Water efficiency• Energy and atmosphere• Materials and resources• Indoor environmental quality• Innovation in design


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


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%



Rating Category



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%



Rating Category



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


Porous PavementsPorous Pavements

Reduce storm water quantity and Reduce storm water quantity and improves water qualityimproves water quality


Porous asphalt Pavements• Conserves water • Allows for better use of

land • Reduces runoff • Promotes infiltration • Cleans stormwater• Replenishes aquifers • Protects streams

Presenter

Presentation Notes

Porous asphalt pavement systems can replace impermeable surfaces for parking lots, roads, walking/biking paths, and other applications. Porous pavements can turn runoff into infiltration; restore the hydrology of a site, or even improve it; improve water quality; and eliminate the need for detention basins.


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

Presenter

Presentation Notes

A typical porous pavement has an open-graded surface over an underlying stone recharge bed. The water drains through the porous asphalt and into the stone bed, then, slowly, infiltrates into the soil. If contaminants were on the surface at the time of the storm, they are swept along with the rainfall through the stone bed. From there they infiltrate into the sub-base so that they are subjected to the natural processes that cleanse water. This slide shows a cross section of a porous HMA pavement. Keys are: Uncompacted subgrade, Clean large size crushed stone with high voids, thin layer of clean ½” crushed aggregate “choker course” that locks up surface to provide stable paving platform.


Presenter

Presentation Notes

In the natural environment, rainfall sinks into the soil, filters through it, and eventually finds its way to streams, ponds, lakes, and underground aquifers. Imagine a one acre parcel of land that receives 45” per year of rainfall. Most infiltrates and returns as evapotranspiration. A small amount runs off. Maybe 15” per year infiltrates. This is what recharges groundwater and keeps streams running.


Presenter

Presentation Notes

The built environment, by way of contrast, seals the surface. Rainwater and snowmelt become runoff which may contribute to flooding. Contaminants are washed from surfaces directly into waterways without undergoing the filtration that nature intended. After development, there is virtually no infiltration and nearly all rainfall runs off impervious surfaces.


Porous asphalt Pavements

Presenter

Presentation Notes

For these reasons, managing stormwater is a significant issue in land use planning and development. Stormwater management tools can serve to mitigate the impact of the built environment on natural hydrology. Unfortunately, however, they also can lead to unsound solutions such as cutting down stands of trees in order to build detention ponds.



Presenter

Presentation Notes

Porous asphalt pavements allow for land development plans that are more thoughtful, harmonious with natural processes, and sustainable. They conserve water, reduce runoff, promote infiltration which cleanses stormwater, replenish aquifers, and protect streams.



Porous HMAConventional HMA

Presenter

Presentation Notes

Porous asphalt pavements are fast and easy to construct. With the proper information, most asphalt plants can easily prepare the mix and general paving contractors can install it. The stone bed, often eighteen to thirty-six inches in depth, provides a tremendous subbase for the pavement. As a result, porous asphalt pavements tend not to exhibit cracking and pothole formation problems. The surface wears well. Under the stone bed is a geotextile which keeps fine particles from moving into the stone bed from below and filling in the spaces.


Water Quality


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


porous streets !porous streets !


porous streets !!porous streets !!



Rating Category



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%


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


Urban Heat Island EffectUrban Heat Island Effect


Urban Heat IslandsUrban Heat Islands

Presenter

Presentation Notes

Many urban areas are up to 10°F warmer than surrounding rural areas, particularly at night. Increased urban temperatures are believed to be caused by a number of factors, including displaced vegetation, heat trapped by tall buildings in “urban canyons,” and waste heat from cars, air conditioners, and factories. In rural areas, evaporation from moisture in soil and vegetation provides a cooling effect.


Urban Heat IslandsUrban Heat Islands


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

Presenter

Presentation Notes

Scientific American, documents that urban heat islands are not a cause of global warming. However, the U.S. EPA says that urban heat islands indirectly contribute to global warming by stimulating greater use of air conditioning, which increases demand for electricity.


myth or reality ?myth or reality ?


reflectivity & temperaturesreflectivity & temperatures


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


0

5

10

15

20

25

30

35

40

New Old (~ 7 years)

Pavement Surface

SRI (

%)

HMA PCC

Tran et al., TRB 2009


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.


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


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 HMA -- The Sustainable The Sustainable

Pavement ChoicePavement Choice

hma - the sustainable pavement choice - apam, asphalt pavement

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