According to the Plastics Pipe Institute, nearly 1 billion pounds of corrugated high-density polyethylene (HDPE) pipe was produced in 2002. This product is noted for its corrosion resistance, high strain allowances, and light weight (equating to easier construction). However, some engineers still are wary of specifying it, citing concerns about requirements for special devices to join the pipe with fittings and valves and about thermal expansion and contraction, among other factors. Regardless of individual opinion, the fact is that the specification of HDPE pipe for drainage applications is on the rise.
For years, the HDPE pipe industry has debated the use of recycled materials in virgin resins. The major concerns are the quality assurance of the materials constituting recycled resins, and therefore the potential for performance variability. Currently, the standard for typical highway applications of drainage pipe, the American Association of State Highway and Transportation Officials (AASHTO) M294, does not allow the use of recycled resin. But that may not always be the case.
According to Bill Bailey, assistant state materials engineer for Virginia and vice-chairman of Technical Section 4B: Flexible and Metallic Pipe under the AASHTO Sub- Committee on Materials, AASHTO is ¬ďnot dead set against recycled resins.¬” He explained that appropriate finished product performance criteria for corrugated HDPE pipe in general are not yet developed (although research indicates that the industry's understanding of the material is ¬ďgetting close¬”). He said, ¬ďYou have to walk before you can run,¬” meaning that fundamental properties have to be understood and standardized finished product tests have to be developed before AASHTO can consider incorporating recycled resins into the standards.
Even as AASHTO continues research and development of tests and standards for HDPE pipe in general, it is moving ahead with efforts to understand recycled resins. In fact, last month AASHTO funded research based on Problem Statement 2006D-2004, ¬ďPerformance and Quality Control of Corrugated Polyethylene Pipe Manufactured from Recycled Polyethylene Material.¬” The ultimate goal of this two- to three-year study is to incorporate findings into the specifications.
While research and standards development continue, along with the debate, manufacturers are producing pipe using recycled resins to satisfy client requests. What's the impetus for interest in such materials? It is the push to incorporate green building practices on all aspects of land development projects. Since more municipalities are setting goals and instituting green standards, the popularity of these alternatives will rise. Check out the cover story, ¬ďMunicipalities LEEDing the way¬” on page 30 to learn the latest trends in municipal sustainability initiatives. Specifying corrugated HDPE pipe made of recycled resins is one example of how project team members can ensure they meet sustainable design initiatives. To learn more about this example, see the feature article, ¬ďRecycled building materials on the rise¬” (page 34), which discusses Hancor, Inc.'s EcoFirst pipe product.
Keep in mind that corrugated HDPE pipe made from recycled resins is just one example of how stormwater collection systems can achieve sustainable design goals. In fact, a popular alternative to corrugated HDPE pipe - concrete pipe - has green advantages as well. Concrete pipe that incorporates re-used byproducts such as fly ash or blast furnace slag are environmentally friendly options.
And, concrete itself is a recyclable material, and therefore can be a good choice for a green product.
As the building industry makes strides to be green, civil engineers must learn to serve their clients and their neighbors in new ways. CE News will be your sustainable education partner. In fact, CE News is sponsoring the Land Development Conference and Expo in Baltimore (May 2005) and Phoenix (November 2005), which highlight sustainable issues.