Michael Pluimer, Richard Thomas
Papers # 2018 Las-Vegas
Over the past decade, there have been several key research projects to evaluate the performance of corrugated HDPE pipes manufactured with post-consumer and postindustrial recycled materials for highway and railroad drainage applications. Three of these projects were recently completed and published (NCHRP Project 4-32, published as NCHRP Research Report 696; NCHRP 4-39 Published as NCHRP Research Report 870; and a PhD dissertation), and they resulted in significant changes to U.S. specifications for these pipes, which now allow the use of post-consumer and postindustrial recycled materials with the addition of several new tests and requirements. The inclusion of recycled materials into these specifications offers owners and users a more sustainable alternative for their highway and railroad drainage applications in the United States.
In 2017, new recommendations were proposed for the American Association of State Highway and Transportation Officials (AASHTO) M 294 standard specification for corrugated polyethylene pipes regarding the incorporation of post-consumer and postindustrial recycled materials into the specification. These recommendations were adopted in 2018 and based on the research and conclusions from two National Cooperative Highway Research Program (NCHRP) projects: Project 4-32, "Performance of Corrugated Pipe Manufactured with Recycled Polyethylene Content", published as NCHRP Report 696; and 4-39, "Field Performance of Corrugated HDPE Pipes Manufactured with Recycled Materials", published as NCHRP Report 870. Additionally, the author's service life prediction model developed in his PhD dissertation on the performance of corrugated HDPE pipes manufactured with post-consumer recycled materials in commuter railroad applications was used to establish minimum criteria for the stress crack resistance properties of pipes manufactured with recycled materials.
This paper provides a summary of the changes to AASHTO M 294 to incorporate the use of recycled materials into the specification, along with the basis for the proposed revisions. The revisions include new requirements for the stress crack resistance of pipes containing recycled materials, including the development of a new test method; a minimum elongation at break requirement when tested in accordance to ASTM D 638; and an OIT requirement when tested in accordance to ASTM D 3895 to ensure proper stabilization to prevent Stage III failures.
The research projects that provided the basis for these changes spanned 11 years and were budgeted for $950,000, making this the most robust body of research on recycled materials for pipe applications published to date. Over 1000 different tests were conducted on 28 different recycled materials and 75 different blends of virgin and recycled materials. 24 full-scale pipes were evaluated, and the service life prediction model was validated on several full-scale pipes in both the field and laboratory. The changes to AASHTO M 294 resulted in the incorporation of more sustainable materials into our drainage infrastructure and will have a lasting positive impact on our society