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TR N EW S 28 8 SE PT EM BE Râ O CT O BE R 20 13 30 The author is Assistant Director, Design, Delaware Department of Transportation, Dover. Recycling Materials and Techniques to Improve Sustainability Delaware Department of Transportationâs Model J I M P A P P A S From project development through delivery,the Delaware Department of Transportation(DOT) works to maintain and develop an infrastructure that is a sustainable asset for current and future use. One of the goals advanced in Delaware DOTâs Mission Statement of Excellence in Transportation is to âminimize the environmental impact of the stateâs transportation system.â The agency is committed to protecting the environment and to planning, constructing, and maintaining a transportation network with increased sustainability. For Delaware DOT, sustainability is defined as economic development that meets the needs of the present generation without compromising the abil- ity of future generations to meet their own needs (1). Most people may not associate highway con- struction with sustainable practices. Sustainability typically conjures up images of recycling house- hold items such as newspapers, plastic and glass bottles, cardboard, batteries, and the like. Yet the road and bridge building industry is a beneficiary of recycled materials and industrial byproducts. Incor- porating these materials into construction projects provides economic, environmental, and engineer- ing benefits for the projects and ultimately for the users of the infrastructure by providing long-lasting roadways. Materials and Technology For example, for the past 20 years, Delaware DOT projects have made use of recycled asphalt pavement and more recently have incorporated other recycled materials, including asphalt shingles, concrete aggre- gate, tire-derived aggregate, crumb rubber, cellulose fibers, and plastic from bottles. The agency also has used industrial byproducts, such as ground, granu- lated blast furnace slag, silica fume, and fly ash in the portland cement concrete placed on projects. In addition, in the past decade, Delaware DOT has specified in-place roadway reclamation and recycling operations for maintaining roadways. The process keeps pavements in place for pulverizing, stabilizing, and reshaping. The reclaimed and recycled pave- ment provides a base course as a stable construction platform for the overlay of pavement materials designed for the roadway. The overlay could be a surface treatment for a low-volume road or a major structural overlay for a higher-volume facility. Delaware DOT has used two in-place reclama- tion and recycling techniques: full-depth reclama- tion and cold in-place recycling. Both techniques pulverize the pavement section to a specified depth and add a stabilizerâsuch as portland cement or emulsified asphaltâto produce a stabilized base for overlays appropriate to the traffic needs. Environmental Sustainability in Transportation P H O TO : B LO G.U D O T.U TA H.G O V Emulsion being added to crushed asphalt in full- depth, in-place asphalt reclamation. Delaware DOT has used this and other materials recycling techniques to âminimize the environmental impacts of the stateâs transportation system.â
TR N EW S 288 SEPTEM BERâO CTO BER 2013 31 Partners and Benefits The success of these recycled materials, industrial byproducts, and in-place reclamation and recycling technologies was achieved with support from indus- try partners, contractors, and the Federal Highway Administration (FHWA), which not only has pro- vided funding but technical support. FHWA is com- mitted to recycling; in February 2002, FHWA formalized a policy that ârecycled materials should get first consideration in overall materials selectionâ (2). Although not a regulation or requirement, the FHWA policy encourages states to use recycled mate- rials or at least to review and consider the possibil- ity of use on projects. Like many other states, Delaware DOT has determined that the use of recy- cled materials, industrial by-products, and in-place reclamation and recycling techniques is beneficial and has incorporated these materials and methods into projects whenever feasible. These environmentally supportable options, how- ever, also are key as Delaware DOT manages limited funding. The department has a fiscal responsibility to the taxpayers of the state to use funds in the most fis- cally responsible way. Over the years, Delaware DOT, like many other agencies, has realized the economic benefits of an extensive recycling programâfor example, significant savings have resulted from using recycled materials and industrial byproducts instead of virgin mixes with no recycled content. Three-E Framework The âtriple bottom lineâ of sustainability balances economic progress, social responsibility, and envi- ronmental protection. Within the transportation industry, the phrase also refers to the three benefits of a recycling program: environment, economics, and engineeringâor the three Eâs. The success of a recycling program is to integrate the three Eâs into the planning, design, construction, operation, and main- tenance of a transportation network to meet the goals of an agency and the needs of the traveling public. Delaware DOTâs recycling program follows the three-E framework: u EnvironmentâBy using in-place materials or reusing materials, Delaware DOT reduces aggregate mining and saves precious natural resources, reduces asphalt refining and cement production, and reduces trucking costs and emissions. Reuse saves the costs of extracting, processing, and transporting virgin materials. u EconomicsâUsing materials that have already been paid for reduces the costs of exporting or importing and handling. The time savings translates to additional monetary savings; moreover, the reduced exposure of workers in a construction zone increases safety. u EngineeringâThrough in-place reclamation and recycling, Delaware DOT can address deterio- rated pavements by stabilizing and strengthening the underlying base pavements; the stable base for over- lays increases long-term pavement performance. Recycled materials and industrial byproducts, more- over, have demonstrated engineering benefitsâfor example, slag cement reduces the permeability of portland cement concrete. Combining environmental, economic, and engi- neering benefits into the project delivery process can have a significant benefit for the transportation infra- structure. Delaware DOT understands the benefits of reusing materials in highway construction and looks for every opportunity to meet the needs of the trav- eling public and to apply sustainable materials and construction practices. This not only benefits users today but users in the futureâa primary goal of a sustainable program. References 1. Epstein, M. J. Making Sustainability Work: Best Practices in Managing and Measuring Corporate Social, Environmental, and Economic Impacts. Berrett-Koehler Publishers, San Francisco, California, 2009. 2. Formal Policy on the Use of Recycled Materials. Federal Highway Administration, 2002. www.fhwa.dot.gov/legsregs/ directives/policy/recmatmemo.htm. Delaware DOT incorporates industrial byproducts such as fly ash (left) and silica fume (right)âboth shown under the microscopeâ into portland cement concrete used in road projects. Recycled materials such as asphalt shingles can be used in asphalt pavement projects. P H O TO S: LEFT, Z EISS M IC R O SC O PY; R IG H T, S ILIC A M A N/W IK IM ED IA C O M M O N S PH O TO : M IS SO U R I D O T