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3The corrugated drainage pipe market in the United States consumes in excess of a billion pounds of virgin high-density polyethylene (HDPE) annually. At the same time, millions of pounds of recyclable HDPE are generated each year. Industry- funded research has demonstrated the feasibility of blending recycled and virgin HDPE to manufacture corrugated drainage pipe. The working hypothesis is that good quality pipe can be manufactured from such blends if critical material properties that affect pipe performance and durability, such as strength and structural properties, density, melt index, environmental stress-crack resistance, and thermal stability are consistently maintained at specified levels in the blends. At present, AASHTO specifications do not permit the use of recycled HDPE in the production of corrugated drainage pipe. Research was needed to 1. Determine if there are blends of virgin and recycled HDPE that meet the current material property requirements spec- ified by AASHTO and defined in ASTM D3350; 2. Perform post-production tests on pipe manufactured with blends of virgin and recycled HDPE to assure its long-term stress-crack resistance and antioxidant effectiveness are equivalent to that of pipe made from virgin HDPE, as cur- rently specified in AASHTO M294 or M252; 3. Identify whether contaminants present in recycled HDPE will adversely affect the long-term service life of finished pipe; 4. To the extent possible, evaluate the performance of existing installations of corrugated drainage pipe produced from blends of virgin and recycled HDPE; and 5. If warranted, develop specifications and test methods to support the use of recycled HDPE in the manufacture of corrugated drainage pipe. The objectives of this study were to 1. Determine the availability, properties, and consistency of recycled HDPE intended for use in the manufacture of corrugated drainage pipe; 2. Prepare blends of recycled HDPE with virgin corrugated pipe resins and determine the properties of the blends; 3. Select candidate resin formulations containing recycled HDPE and manufacture 12-in.-diameter, dual wall, cor- rugated pipe from the blends; 4. Determine the short- and long-term properties of the blends and evaluate if the currently used design standards can be used for recycled-containing pipe; and 5. Prepare specifications and standard test methods for resins and pipe that contain recycled HDPE. C H A P T E R 1 Introduction
