Advancements in the Experimental Study for the Design and Classification of Cured In Place Pipe (CIPP) Liners

Abstract

Thermoset Cured In Place Pipe (CIPP) liners have been used extensively in North America to rehabilitate aging buried gravity and watermain pipe networks. The design and performance assessment of CIPP requires a good understanding of its short- and long-term material properties. Unfortunately, the material properties of CIPP have not been studied extensively. This study presents the results of the experimental investigations completed on reinforced and non-reinforced CIPP liners to better understand some of their material properties such as Long-Term Flexural Strengths (LTFS), Strength Retention Factors (SRF), Short-Term Burst Strengths, and Long-Term Hydrostatic Burst properties. Short-term flexural tests and 10,000-hour flexural creep-rupture tests were completed on both reinforced and non-reinforced CIPP flat coupon specimens and the results were plotted and extrapolated to determine their short-term flexural strengths and 50-year (expected service life) LTFS respectively. The LTFS for non-reinforced CIPP liners was determined to be 83.3% - 84.4% of the first break stress. Reinforced CIPP test samples were found to sustain applied stress without failure up to 5% strain limit, and that creep failure will not occur in reinforced CIPP specimens load to 95 percent of the ASTM D790 short-term yield stress. The long-term SRFs of both reinforced and non-reinforced CIPP are greater than the typically applied 50% retention factor. Full-scale reinforced CIPP pressure liners used for the renovation of watermains were tested using a University of Waterloo designed, built, validated, and commissioned burst testing facility. Short-term burst tests were completed on 150mm and 200mm OD CIPP pressure liners and their short-term burst pressures were determined. Long-term hydrostatic tests were completed on the 200mm OD CIPP pressure liners using the Hydrostatic Design Basis (HDB) standard testing methods. This is in line with the industry-recognized design and classification standard used for other watermain renovation products such as PVC, HDPE, and GRP. The long-term material properties of CIPP pressure liners such as Long-term Hydrostatic Strengths (LTHS), Hydrostatic Design Basis (HDB) stress, Hydrostatic Design Stress (HDS), and Pressure Rating (PR) were determined. The long-term hydrostatic properties of CIPP pressure liners compared well with those of other watermain renovation products. This establishes the HDB design and classification approach as appropriate for designing and classifying CIPP pressure liners. HDB testing found that the CIPP liners is approximately 4 times lower than the short-term burst value.