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Chapter 3
Designing for Environmental Stewardship in Construction & Maintenance
3.12. Design and Specification for Recycling

3.12.1 The Growing Need for and Importance of Waste Minimization and Recycling

Recycling means reintroducing waste material into the production process, to supplement primary resources. The use of waste as a raw material saves resources and primary raw material, reduces air and water pollution, and extends limited landfill life. Recycled products can also save financial resources through lower material costs and lower disposal costs. In some cases, using recycled products can improve material performance as well. Consequently, using recycled materials is a key aspect of more efficient and environmentally sensitive highway design and construction. [N]

Recycling also saves energy. A quantitative assessment of environmental impacts on life cycle of highways found that most energy is consumed in the manufacturing stage of construction materials, with consumption of 1,525 tons of oil equivalent (TOE)/functional unit (1 km and 4 lanes of highway). [N] Energy consumption in the maintenance and repair stage was also fairly high among the life cycle stages; the next highest consumption was for the construction and demolition stage. Through the whole life cycle of 20 years, 2,676 TOE of energy/functional unit was consumed, and this corresponds to SO2, NOx, and CO2 emissions of 62.1 tons, 17.1 tons, and 2,438.5 T-C, respectively. [N]

The United States spends approximately $13 billion annually (1999 dollars) on highway construction and repairs, requiring nearly 350 million tons of both natural and manufactured construction materials. [N] Approximately 4.1 billion metric tons of non-hazardous solid waste materials are generated annually. The majority of these materials are being landfilled in many states; however, landfills and access to materials are increasingly limited by growing environmental regulations and permitting requirements, restrictive zoning laws, land uses, and other economic considerations. Community opposition has restricted the expansion of and forced the closure of existing landfills, quarries, and gravel pit operations. The latter has created localized shortages of construction aggregates and borrow materials in some areas, further adding incentive to explore alternatives in order to alleviate such shortages and to conserve natural resources.


3.12.2 Common Recycling Applications in the U.S. and Europe
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Research into new and innovative uses of waste materials is continually advancing. Many highway agencies and private organizations have completed or are in the process of completing studies and projects concerning the feasibility, environmental suitability, and performance of using recycled products in highway construction. Reduction of waste material at its source and reuse of construction waste complement recycling efforts.

Recycled materials are typically used in such applications as bituminous pavements, Portland cement concrete (PCC) pavements, road base, embankments and fills, flowable fills, landscaping, bicycle paths, parking lots, and appurtenances such as signs, fencing, barriers, traffic delineators, etc. Some of the most notable uses of recycled materials in the highway environment over the last 20 years have included recycled asphalt pavement (RAP), reclaimed concrete pavement, coal fly ash and blast furnace slag. A few states and local governments have passed legislation to promote recycling in road construction. In some case beneficial use determination processes (BUDs) evaluate uses though a wide range of approaches are used; California, Illinois, Massachusetts, New Jersey and Pennsylvania are working to standardize the BUD process and create reciprocity. State DOTs and state environmental protection agencies (State EPAs) are also trying to balance the desire for increased use of recycled materials with concerns about potential environmental impacts of leaching from recycled materials.

FHWA produced a review of the use of recycled materials in highway construction in the early 90s, a summary of which is included below. [N]

Table 11 : FHWA Summary of Known Uses in Waste Applications

Table 11 Thumbnail
Adobe Acrobat file View Table 11: FHWA Summary of Known Uses in Waste Applications

NCHRP Synthesis of Highway Practice 199, Recycling and Use of Waste Materials and By-Products in Highway Construction. [N] developed a methodology for assessing the suitability and practicability of specific waste resource materials in transportation applications, determining appropriate uses, developing design and construction guidelines, and evaluating long-term in-service performance and applied the methodology to a spectrum of waste resource materials. The project developed a comprehensive CD-database including material and engineering properties; environmental information; legislative, regulatory, and litigation information; history of past use and performance; references to existing specifications and guidelines; information on material generation (source, quantity, existing inventory); and information on ongoing research and demonstration projects. [N]

Congress has supported development of a Recycled Materials Resource Center (RMRC) at the University of New Hampshire to perform research and outreach to reduce barriers to recycling in a highway environment. FHWA and RMRC produced a 2001 manual to provide guidance to assist transportation agencies in the maintenance of high-quality roads that perform to high engineering standards over their design life, without future problems, and to promote cooperative efforts with environmental agencies to ensure that present and future environmental problems do not arise when recycled materials are used in highway infrastructure. Read the Framework for Evaluating Use of Recycled Materials in the Highway Environment online. [N] . The private sector is also developing innovations in processing and applications.

In 1999, FHWA, AASHTO, and NCHRP sponsored an international scan tour to Denmark, Sweden, Germany, the Netherlands, and France to review and document innovative policies, programs and techniques in Europe and make recommendations that would lead to the reduction of barriers to recycled material use. In particular the scanning team sought applications in highway construction in the ROW (e.g., roads, shoulders, medians, bridges, culverts, swales, appurtenances) though activities associated with highway construction can also result in use of recycled materials outside the highway ROW. In Europe, government policies and regulations such as bans on landfilling, landfill taxes, and natural aggregate taxes support recycling. Generally, clear and unambiguous engineering and environmental test methods and performance standards help to reduce uncertainty and allow recycled materials to compete with natural materials. Where tests and standards do not exist, governments often support recycling by sharing risk.

In the U.S. there are widespread needs for clear engineering and environmental test methods and performance standards. The owner or contractor generally assumes risk. The States, academia and the private sector are conducting significant research. In the U.S. some recycled materials like RAP, coal fly ash and blast furnace slag are widely used in a true free market situation because of their excellent performance and competitive costs. Other materials are used more locally in response to more specific local market forces. There is little federal government involvement, except for construction procurement guidelines for materials like coal fly ash. Rather, the situation is driven at the state level. For example, the State of Pennsylvania has adopted legislation to promote recycling in the highway environment. RMRC's Report for the International Scan Tour on Recycling Techniques, is available on-line. [N]


3.12.3 General Recommendations for DOTs with Regard to Recycling and Waste Management
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The International Scan Tour Report generated a number of recommendations for AASHTO's Standing Committee on the Environment and Subcommittee on Materials that are pertinent to recommended practices for state DOTs: [N]

  • Include a recycling strategy in the sustainability aspect of strategic plans and long range research priorities.
  • Create a framework to consider the use of recycled materials in project planning, alternatives analysis, and mitigation analysis.
  • Encourage long term materials supply plans and recycled materials availability plans.
  • Develop clear engineering and environmental guidelines at the State and Federal level that are available for suppliers and decision-makers.
  • Develop courses on recycling.
  • Evaluate contractors with respect to use of recycled materials or environmental protection during contract performance reviews.
  • Develop and implement the use of warranty and performance based specifications. [N]

The following practices are also recommended to facilitate environmental stewardship in materials management: [N]

Materials should be used in the most effective way possible.

  • Structures should have long lives.
  • Materials should be recyclable.
  • Consumption of energy in the construction development should be optimized.
  • Alternatives for conventional resources should be considered.


3.12.4 Life Cycle Cost-Benefit Analysis
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The most recent TRB research needs meeting called for an expansion of life cycle analysis to reduce waste, prevent pollution, and encourage recycling. [N]

FHWA's Highway Economic Requirements System (HERS) is an example of a tool that supports tradeoffs between preservation and improvement projects. The HERS application is based on the Highway Performance Monitoring System (HPMS) database, and is intended to replace HPMS as the source of biennial federal needs studies submitted to Congress. The HERS algorithms address both highway capacity and pavement preservation needs. Thus, state application of HERS or HERS/ST are uniquely suited to asset management studies that are more comprehensive than those addressed by individual management systems (e.g., pavement management and congestion management) and can explore tradeoffs between system preservation and system improvement or expansion.


3.12.5 Areas for Recycling Applications
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Areas for recycling applications in maintenance, many of which are applicable for other parts of the organization, are described in detail in Section 10.13.


3.12.6 Specifications for Recycled Materials in Transportation Applications
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Available AASHTO or DOT specifications for the recycled materials covered in ensuing sections are included as web links within those sections, and more specifications are being developed all the time. The Recycled Materials Resource Center (RMRC) has a project underway to Develop and Prepare Specifications for Recycled Materials in Transportation Applications. Participants in the project - Caltrans, FDOT, Illinois DOT, Mass Highway, Michigan DOT, Mn/DOT, NHDOT, NJDOT, NYSDOT, NCDOT, Ohio DOT, PennDOT, TxDOT, and WisDOT - identified the recycled materials of greatest interest to DOTs and assisted in the development of specifications. Six material/application combinations are underway. The first of these, a specification for glass cullet use as an aggregate base course, was published in 2001 (M-318-01). This past year, a second specification, "M-319-02, Reclaimed Concrete Aggregate for Unbound Soil-Aggregate Base Course," was published in the 22nd edition of the AASHTO's Standard Specifications for Transportation Materials and Methods of Sampling and Testing. A third specification, "Use of Recycled Concrete as an Aggregate Substitute in PCC Pavements," is under review by the AASHTO Technical Section. A specification for coal fly ash in embankments has been tabled by the Technical Section, while a draft specification for reclaimed asphalt pavement as an aggregate in asphalt concrete has been prepared for submission to the Technical Section. The last specification on the use of roofing shingle scrap as an aggregate for asphalt concrete is in preparation.

See also:

As of February, 2004, specifications under development via RMRC projects include the projects listed in the Appendix. RMRC keeps an updated list at their RMRC Resources and Specifications site. [N]


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Continue to Section 3.13 »
Table of Contents
Chapter 3
Designing for Environmental Stewardship in Construction & Maintenance
3.1 Beyond Mitigation: Projects to Achieve Environmental Goals
3.2 Context Sensitive Design/Solutions
3.3 Avoiding Impacts to Historic Sites
3.4 Designing to Accommodate Wildlife, Habitat Connectivity, and Safe Crossings
3.5 Culverts and Fish Passage
3.6 Stream Restoration and Bioengineering
3.7 Design Guidance for Stormwater and Erosion & Sedimentation Control
3.8 Drainage Ditches, Berms, Dikes, and Swales
3.9 Design for Sustainable, Low Maintenance Roadsides
3.10 Designing to Reduce Snow, Ice, and Chemical Accumulation
3.11 Designing to Minimize Air Quality Problems
3.12 Design and Specification for Recycling
3.13 Designing to Minimize Noise
3.14 Lighting Control/Minimization
3.15 Design for Sustainability and Energy Conservation
3.16 Safety Rest Areas, Traveler Services, and Parking Area Design
Lists: Examples | Tables | Figures
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