Making Good Environmental AND Economic Decisions Through … · 2017-05-02 · Recycled asphalt...
Transcript of Making Good Environmental AND Economic Decisions Through … · 2017-05-02 · Recycled asphalt...
Making Good Environmental AND
Economic Decisions Through Sustainable Pavement Practices
Thomas Van Dam, P.E., Ph.D.
Principal Engineer
May 21, 2013
2013 IBTTA O&M Congress Portland, Maine
Conceptually, sustainability is not difficult to understand A sustainable activity can be done for
perpetuity without diminishing the resource or degrading the environment
Often it is defined as a balance between economic, environmental, and social factors
In practice, a clear and simple definition is elusive
What is Sustainability?
Keeping It Simple
Sustainability balances: Economic factors Environmental factors Social factors
Must consider these factors over the life-cycle Pavement life is most often
assumed to be 50 years in most analyses
EconomicGrowth
EnvironmentalStewardship
SocialProgress
Sustainable
Sustainability It is simply good engineering It entails working with limited resources to
achieve design objectives It is not about perfection, but instead about
balancing competing, and often contradictory, interests
The Life Cycle: A Key Concept
Renewal
Is Asphalt or Concrete a More Sustainable Paving Material?
Yes It depends on the context and how
sustainability is defined The models currently lack the accuracy to
make a definitive choice All studies have caveats and limitations
The situation is dynamic This is the wrong question!
The Right Question Is “How Can We Make Pavements Better?”
New Manual of Practice for Sustainable Pavements is
Under Development
FHWA Sustainable Pavements Program
Long-life/durable Use of recycled and industrial byproduct
materials Smooth, quiet, and safe over the life-
cycle Maintenance/Preservation
Cost effective, environmentally sound, and community friendly
Attributes of Pavements Consistent With Sustainability
Sustainability is not an accident Purposefully design sustainable features into
the pavement Must think cradle to cradle
Understand and design for the needs of the stakeholders Context sensitive design
Design for what you need using the best tools available
Design to be Sustainable
Long-life pavements 40 years or more Consider future maintenance,
rehabilitation, and recycling Use AASHTO Pavement ME Design Guide
for Highways Sensitive to climate, traffic, and materials
Design to be Sustainable
Example: Two-Lift Concrete Pavement
Example: Perpetual Asphalt Pavement
Maximize the use of recycled/industrial byproduct materials Binder replacement is most effective
Maximize the use of local materials Good economically and good
environmentally as long as performance is not compromised
Remember: Transportation is energy and emissions
Material Choices
Recycled asphalt pavement (RAP) Crumb tire rubber Recycled asphalt shingles (RAS) Warm-mix asphalt (WMA)technologies Potentially huge environmental benefits and
enhanced performance Must consider all upstream environmental
costs Improved asphalt Thinner pavements Increased longevity
Asphalt Options
Recycled concrete aggregates and RAP Reduce cement content of concrete
paving mixtures through improved design Increase use of SCMs such as fly ash and
slag cement Blended cements
Reduce concrete Better design Increased longevity
Concrete Options
Cement Content and CO2 Po
unds
CO
2/yd
3
Energy use and emissions from vehicles has the largest environmental impact over the pavement’s life
Vehicle fuel consumption is impacted by the pavement Pavements should be smooth Pavement stiffness impacts rolling
resistance at slow speeds
Vehicle Operating Costs
Desire low maintenance and long life Low impact preventive maintenance that
keep pavements smooth, quiet, and safe are ideal e.g. microsurfacing asphalt and diamond
grinding concrete has large potential Overlays are an excellent rehabilitation
alternative to extend pavement service life Both concrete and asphalt
Pavement Renewal
Typical pavement performance curve showing ideal times for the application of pavement preservation, rehabilitation, and reconstruction (Smith, Hoerner, and Peshkin 2008)
Pavement Renewal Concepts
Preventive Maintenance Concept
Milling and resurfacing Can do very thin overlays if pavement
structure is sound Reduce noise and increase friction
Microsurfacing can be effectively used Consider surface reflectivity? Concrete overlays becoming more
common
Asphalt Options
Applied after partial-depth, full-depth repair and load transfer restoration
Diamond embedded blades remove a thin layer of concrete from the surface
Treatment removes faulting, wheel path wear, warping/curling, and irregularities
Restores pavement ride quality, improves skid resistance, and very quiet
Concrete Option: Diamond Grinding
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Background
Why Quantify? If it is not quantified, it is not valued Without value there is no incentive Without incentive, it won’t get done
Without quantifying it, it cannot be improved upon
Must quantify economic, environmental, and social impacts
A rigorous LCCA will include ALL cost incurred over the pavement’s life Uses a discount rate to account for the time
value of money Economic elements of the sustainability
framework addressed through LCCA
Economics: Life Cycle Cost Analysis (LCCA)
Environmental and social impacts can be assessed using rating systems Greenroads™, INVEST, GreenLITES Gaining popularity
Tools for environmental life cycle assessment (LCA) are emerging Illinois Tollway is currently developing in-
house system
Assessing Environmental and Social Impacts
Comparison of Alternatives Using LCA
1. Alt #1 2. Alt #2
GWP Human Toxicity Energy Waste
Sustainability requires balancing economic, environmental and social needs
Multiple asphalt and concrete strategies exist in design, materials, and maintenance/rehabilitation to improve sustainability Lots of low hanging fruit available Construct to maintain
Summary
Requires thought and commitment Cannot be business as usual
Quantifying sustainability over the life cycle is essential Must be able to quantify in order to
improve Not about comparing, but instead
improving
Summary
Questions