Evaluation of Corrugated HDPE Pipes Manufactured with Recycled Content underneath Railroads

Corrugated high-density polyethylene (HDPE) pipes are an attractive product for culvert and drainage applications in the railroad industry due to their resistance to corrosion and abrasion, long service life, and flexibility. Railroad specifications currently require these pipes to be manufactured with 100% virgin materials. However, due to the push for more sustainable and cost-effective engineering materials and practices, the railroad industry would benefit from using pipes made with recycled content provided their long-term performance was equivalent to pipes made with virgin materials. To evaluate the performance of corrugated HDPE pipes made with recycled content in rail applications, a pilot study was conducted with the Southeastern Pennsylvania Transit Authority (SEPTA). The study was funded cooperatively by SEPTA and the National Cooperative Highway Research Program (NCHRP) Project 4-39. Two 30-inch diameter corrugated HDPE pipes, one manufactured with 100% virgin materials and one manufactured with post-consumer recycled content, were installed underneath a regional commuter rail line in northeast Philadelphia with 2 feet of cover from the top of the pipe to the bottom of the railroad tie. The pipes were instrumented with strain gages and extensometers to record live-load data and monitor the pipes over time. A laboratory study was also developed to assess the long-term durability of pipes made with recycled content with regards to cyclical live loads. The pipes have been in service for over 1 year and are performing as designed, with no change in performance since the date of installation. This was a groundbreaking study as it included the first corrugated HDPE pipe manufactured with post-consumer recycled content installed underneath one of SEPTA's regional commuter lines. The research project is a key component of SEPTA's ongoing sustainability initiatives.