Making Inroads

Recycling and reusing materials helps to extend limited natural resources. Approximately 2 billion tons of aggregate are used annually, and the demand is expected to increase 25 percent by the year 2020. New sources of quality aggregates are difficult to find, and it is even more difficult to obtain permits to mine them. It is reasonable to assume that if quality materials were used originally, quality materials should exist when they are recycled back into the same product, or into a different product.

Furthermore, given the size of the nation’s transportation network, large volumes of potential materials available for recycling exist. Waste disposal areas are also difficult to find, especially in crowded urban areas. Recycling can therefore help reduce costs in some instances. In addition, from an environmental stewardship viewpoint, recycling is simply the right thing to do.

Understanding the roles of all stakeholders is important in order to develop the partnership. A materials engineer with a state DOT has the ultimate responsibility for the quality of materials and manufactured products incorporated into the state’s transportation system. Therefore, when making decisions about the use of a new recycled material, the materials engineer seeks to understand the facts, any performance models and the probability of success.

The AASHTO Subcommittee on Materials is comprised of the state materials engineers from all states and is responsible for the annual publication of materials specifications, recommended practices and test methods. These are routinely referenced and included in project specifications for state DOTs and are referenced by many municipalities and other organizations.

Recent approvals include glass cullet for aggregate base; reclaimed concrete for aggregate base and two standards for using compost for erosion control applications. Pending actions include: reclaimed concrete aggregate for use in PCC; coal fly ash embankments; recycled asphalt shingles in HMA and a recommended practice for evaluating the engineering and environmental suitability of recycled materials.

The AASHTO Subcommittee on Materials created a Recycling Task Force in 2002 to help guide the development of specifications and test methods. The task force serves as a focal point for other efforts, such as the FHWA Recycling Team, the Recycled Materials Resource Center, industry ideas and various research efforts. The task force is charged with helping to implement standards for recycled materials considering engineering principles, environmental stewardship and economic feasibility.

Industry serves a critical role in successfully utilizing recycled materials. Manufacturers, producers and contractors are encouraged to bring innovative ideas to states for consideration.

States need some type of proof of concept from research or trials when presented. Experience in the use of recycled materials and products in non-transportation venues needs to be shared with the states to showcase how they can be successfully used. States may be open to some type of cooperative effort to evaluate a new product. Industry should approach a state armed with an understanding of the benefits as well as any limitations of their material or product, including any environmental concerns, and communicate openly with the state.

I believe that all stakeholders, including the environmental agencies, have similar mutual goals. We all want a quality product that meets the specification requirements in an economical and environmentally sound way.

Communication is the key. All stakeholders should seek to understand each other’s viewpoints, timetables and needs. If we truly do that, I am convinced that continued progress will be made and more recycled materials will be used. My goal is to see more recycled products being recognized as an industry standard, with desirable properties that are equal to, or exceed those of virgin materials.

Success stories exist where recycled materials have certainly become the industry standard and are more economical than without recycling. Hot mix asphalt (HMA) is one such example. Approximately 80 percent of HMA is recycled back into highways and, according to FHWA, is the single most recycled material in the world. It is a proven technology that is economically sound and used by most states. It can also include other recycled materials, such as shingles, glass, crushed concrete and rubber.

Concrete is another successfully recycled material. It is believed to be the second most recycled material in the world with approximately 120 million tons of concrete debris available annually. It can be used as an aggregate base course material as well as incorporated into new concrete.

Many other recycling opportunities exist, such as coal fly ash. It can be used as a substitution for portland cement in concrete, which enhances the longevity and durability at a reduced cost. It can also be used as mineral filler in HMA, in flowable fill material and in the construction of embankments.

Tires can be shredded and used in embankments, as crumb rubber in HMA and noise walls, as ballast for traffic drums and can be used as rubber mulch.

Other products such as foundry sand, glass cullet, recycled plastic and compost are routinely used. The use of recycled materials has unlimited potential.

I believe that if we talk to each other and really seek to understand each other’s needs, more successful uses of recycled materials will be the result. Opportunities exist for innovative uses to provide materials that will become a future industry standard, with enhanced properties that will be the economic choice of agencies specifying materials. My challenge is this: Let’s all work together to close the loop and make it happen.