A novel test procedure for evaluating the performance of composite cured-in-place-pipe liners in water pressure pipe rehabilitation

The cured-in-place pipe (CIPP) is a pipe rehabilitation technique that is becoming increasingly popular due to its cost advantages, reduced environmental impact, and decreased time requirements compared to traditional pipe replacement. However, some CIPP rehabilitation projects have revealed deficiencies in predicted liner performance. This paper proposes and validates the Inner Balloon Pressure Test, a new test procedure for the quality control of CIPP rehabilitation liners. The test is intended to replicate the working stress conditions of an installed CIPP liner, and is proposed as an alternative to the curved specimen bending test recommended by the current CIPP standard and which has been shown to overestimate the ultimate stresses of cured CIPP liner specimens by more than 200%. Consequently, in a liner of DN 385 and 6 mm of thickness, a burst pressure of 138.2 bar was predicted through the bending test, whereas 62.8 bar was deducted from tensile tests. The experimental evidence provided in this study can significantly impact the design of CIPP pressure pipe liners. Inadequate sizing of the structural reinforcement can compromise the liner functionality and the rehabilitation of the pipeline. Therefore, this study provides a novel test that reduces uncertainties related to the strength analysis of CIPP liners. Furthermore, it contributes to optimizing and advancing existing design and quality control techniques.