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