Laboratory Evaluations of Corrugated HDPE Pipes Containing Postconsumer Recycled Material under Constant Deflection Conditions

In recent years, incorporation of recycled material in the production of large-diameter plastic drainage pipes for nonagricultural purposes has gradually increased. With this new development, AASHTO began allowing corrugated high-density polyethylene (HDPE) pipes manufactured with postconsumer recycled (PCR) materials to be installed as culverts under major highways, despite the fact that such pipes may contain impurities and their long-term behavior still is not fully understood. This paper presents a test program in which HDPE pipes with varied recycled material contents were subjected to forced long-term constant vertical deflection of 20%. Eight HDPE pipe specimens with inside diameter of either 610 mm (24 in.) or 762 mm (30 in.) were kept in a compressed state in the laboratory for 2 years. The maximum tensile strain was found to be about 3% for all pipes. No cracks were seen in the 0% and 49% PCR-content pipes during the 2-year test duration. However, the 98% PCR-content pipe developed longitudinal cracks at the crown position inside after 101 days and additional longitudinal cracks at the springline position outside after 131 days. In addition, tensile strength tests were performed on dog-bone specimens taken from untested HDPE pipe specimens with PCR contents of 0%, 49%, and 98%. The results showed that the tensile test behaviors were similar in the 0% and 49% PCR-content HDPE materials, but the material ductility significantly diminished at 98% PCR content.