Part 7: Culverts and Hydraulic Structures: Stress Crack Resistance of Corrugated High-Density Polyethylene Pipes in Different Test Environments and Temperatures

Abstract

Corrugated high-density polyethylene (HDPE) pipe 36 in. (900 mm) in diameter was evaluated for its stress crack resistance with the notched constant ligament stress test (ASTM F 2136). Test specimens were taken directly from the pipe liner to include the processing effects. In addition to the standard test condition of 10% Igepal solution at 50°C, tests were performed in water and air at temperatures of 60°, 70°, and 80°C. The test data were analyzed with the ISO 9080 method to define the transition point and ductile-to-brittle curve. The results indicate that the 10% Igepal solution greatly accelerates the stress cracking process, whereas the stress cracking behavior in water and in air is aggressive and practically the same. Activation energies in both ductile and brittle portions of the curve are in general agreement with the literature for HDPE resins. The results indicate that the rate processing method is an accurate model with which to extrapolate data from elevated test temperatures to lower service temperatures. However, Popelar's shift method tends to overestimate the failure times.