The purpose of this study was to conduct a field evaluation of polypropylene pipes in order to assess their potential suitability for drainage applications. The specific objectives were (1) to document the product handling during installation, and (2) to evaluate the in-situ performance under service conditions.
The Virginia Department of Transportation (VDOT) selected five test locations on low-volume rural roads in Albemarle County where the field evaluation would occur. Installation of the pipes was carried out by a VDOT maintenance crew. In all cases, polypropylene drainage pipes replaced the existing corrugated metal and concrete pipes that had reached the end of their service life. No material testing of any kind was carried out on the pipes. It was understood that the limited scope of the study would not result in any conclusive assessment regarding the particular product’s potential long-term performance.
The dual and triple wall plastic pipes with nominal diameters of 30 and 48 in were supplied by ADS, Inc. The installation process was documented, and periodic field observations were conducted during the subsequent 1 year of service. As part of the evaluation, cross-sectional measurements were conducted at 2.5-ft intervals on all installed pipes.
The results indicated that after 1 year of service, the maximum deformations of all pipes were less than 5 percent, satisfying current VDOT post-installation inspection requirements. No signs of crushing, buckling, or material degradation were detected.
The results of the study indicate that polypropylene pipe offers a number of potential benefits when used in drainage applications. The durability of a plastic pipe must be resolved adequately in order to facilitate widespread product usage. In the case of polypropylene pipe, the issue of degradation attributable to material oxidation is extremely important. For many transportation projects, the owner must have a reasonable degree of assurance that the material will perform satisfactorily for at least 50 years. Fortunately, test methods for the durability assessment are currently available. It is possible that as users become more familiar with polypropylene pipe, they will increasingly regard it as a viable alternative in terms of life cycle costs. The product appears to lend itself to further evaluation as a promising innovative design.
The report provides recommendations regarding the potential future acceptance protocol for polypropylene pipes on culvert and storm sewer projects. The recommendations include a durability assessment by an independent laboratory and a field verification of performance on the VDOT network.