A Route to Recycling

Features - Feature

Illinois road builders and transportation system designers have put together a road map for increased recycling opportunities.

January 18, 2011
Brian Taylor

Working in coordination, the Illinois Department of Transportation (IDOT) and the Illinois Joint Sustainability Group released a 70-page document called “I-LAST: Illinois Livable and Sustainable Transportation Rating System and Guide,” in early 2010.

The Joint Sustainability Group includes the Association of Consulting Engineers Companies - Illinois (ACEC-IL) and the Illinois Road and Transportation Builders Association (IRTBA), trade associations whose member companies design and build roads and manage other transportation projects.

Together, these groups are also working on an accompanying document called the I-LAST Construction Practices Addendum.

According to Beth Tatro of the IRTBA, “The Illinois Livable and Sustainable Transportation (I-LAST) Manual is modeled after the USGBC’s LEED green building certification program and establishes sustainability design and construction guidelines and a scoring system for road and transportation projects.”

Tatro says, “Illinois is among a few states in the forefront of providing this kind of framework for recognizing and encouraging green practices across all key aspects of road and transportation building.”

This addendum to the I-LAST Guide is under development and is likely to build on several aspects of it, including the section on materials.

More than 5 pages of the original I-LAST Guide were devoted to the subject of materials choices and ways to use materials in environmentally beneficial ways.

The section is introduced by offering the I-LAST Guide’s objectives when it comes to materials use and choices:

• preserving natural resources and protecting the environment by reducing the use of natural resources and increasing the use of recycle/reuse materials;
• finding ways to reduce emissions by minimizing hauling;
• building cost effective pavement systems by using recycled and/or reused materials; and
• providing support for innovative thinking to create sustainable pavement systems.

Several material specifications already exist within the framework of IDOT Standard Specifications, Special Provisions, District Special Provisions and other IDOT-approved provisions, the groups note.

Numerous practices involving the recycling and re-use of materials are further identified in the I-LAST Guide, including:

• Reuse of top soil, which can be accomplished by reusing top soil removed for grading and deploying it on site, “as long as it is determined non-hazardous material,” according to the Guide
• Reuse of spoils (the earthen materials beneath topsoil) within a project corridor to minimize the trucking of material into and out of the site

Each of these techniques can be considered not only environmentally beneficial, the I-LAST authors point out, but, “reducing the transportation may also reduce the construction costs.”

Several other items in the Materials section of the I-LAST Guide refer to the production of secondary aggregates and other crushing and recycling techniques.

Among the ways to earn I-LAST points as spelled out in the Guide are to allow for the crushing and recycling of concrete shoulder and concrete pavements. As with topsoils and earth, the practice can “minimize the hauling of useable construction material from the site for processing and hauling back for reuse, to potentially minimize pollution, emission, and to potentially extend the use of natural resources,” note the I-LAST authors.

Also appearing on the I-LAST list is allowing flexibility in design with the use of recycled or salvaged non-hazardous material. Among the benefits, according to the authors, is to “build cost-effective structures.”

This I-LAST Materials item is broken down into several sub-sections pertaining to specific materials, including:

• the processing of demolished concrete to reclaim scrap metals and to create useable aggregate;
• the use of milled HMA (hot mixed asphalt) pavements for capping stone;
• the use of recycled crushed pavements for temporary aggregate for areas like driveways or access roads;
• the use of recycled crushed pavements for shoulder stone;
• the use of recycled crushed pavements as aggregate for sub-grade, sub-base or base lifts;
• reclaiming sub-base granular material; and
• providing for the optional reuse of recycled-content or scrap materials for items such as metal sheeting, guard rails, etc.

Should the I-LAST document gain attention with planners of an increasing number of highway projects in Illinois (and then beyond), it should only help the cause of companies that provide concrete and asphalt crushing services.

Several other materials-related items in the I-LAST Guide pertain to methods, practices and choices that may offer further opportunities to recycled aggregates producers and mixed C&D recyclers who produce screened, recycled-content soils and filler material.

These include:

• allow the use of recycled asphalt pavement (RAP) in the construction of new hot mix asphalt pavements;
• allow the use of recycled asphalt shingles (RAS) in the production of stone matrix asphalt (SMA) mixtures;
• allowing the use of locally produced by-products (such as foundry sand) to be re-used in the construction of embankments, hot mix asphalt and portland cement concrete mixtures;
• consider providing for the use of ternary concrete mixtures that incorporate fly ash, slag cement, or micro-silica as a partial substrate to cement in the production of concrete mixtures. The use of these additional cementitious materials can help to reduce emissions, energy consumption and virgin material requirements;
• provide for the use of alternative materials in the construction of embankments as partial additions to or replacement of natural aggregates;
• allow the use of slag aggregate in the production of HMA mixtures; and
• implement a project-specific plan for the innovative reuse of waste materials other than the ones listed above.

The environmental benefits of this collection of practices are numerous, the I-LAST authors write.

The use of RAP in particular is cited as environmentally-friendly, with a number of benefits cited, including less dumping of RAP in landfills and (again) reducing pollution by minimizing trucking and hauling of material to landfills.

The hauling of materials that cannot be recycled on site not to a landfill but to a permitted recycling site can also earn a contractor points under the I-LAST guidelines. The document refers to Illinois Environmental Protection Agency-approved recycling sites as being one option, as well as the use of “contract documents that identify other state/public entities or non-profit organizations.”

Recycling companies that provide soil stabilization materials can also benefit from two points that can be earned for the use of recycled-content materials in this application.

The I-LAST Construction Practices Addendum scheduled to be completed in 2011 is likely to build upon the practices laid out in the text above.