Watertightness of CFRP Liners for Distressed Pipes

Abstract

Hydrostatic pressure tests of prestressed concrete cylinder pipe (PCCP) with bands of broken wires and lined with carbon fiber reinforced polymer (CFRP) have shown that certain CFRP laminates used as liners for remediation of distressed PCCP may not be watertight. Such test indicated the need to investigate the watertightness of CFRP laminates without expensive hydrotesting of full lengths of CFRP-lined distressed pipe. To address this need, the authors developed a special watertightness pressure chamber that allows testing of curved CFRP laminates, similar in geometry to a segment of CFRP liner installed in a rigid pipe, to pressures up to 500 psi. The pressure chamber simulates the stress state in the CFRP liner installed inside a pipe degraded to the extent that it does not resist the radial motion of the CFRP liner within a window. A number of watertightness concepts were developed, and CFRP specimens were built and tested. The results of the watertightness tests are presented along with the provisions for watertightness of CFRP liners. The procedure for qualification of different laminates for watertightness is discussed.