Rationale

ASTM C497 does not refer to “failure” as the test itself doesn’t establish passing or failing, rather it determines the 3EB strength of the pipe at the time of testing. Similarly, ASTM C39 does not refer to “failure” as the test itself doesn’t establish passing or failing, rather it determines the concrete’s compressive strength at the time of testing. However, ASTM C76 penalizes the manufacturer should they test pipe early and fail: they are then required to test and pass two pipe for every pipe that “failed”. This methodology does not account for any strength gain in the pipe between “failing” and “passing” tests. Based on literature, concrete gains strength rapidly at early ages (28 days), with the rate of strength gain continuing after 28 days, but at a slower rate. Accordingly, we believe that pipe tested at 28 days of age or less should be exempt from additional testing if retested more than 24 hours after the initial test. This exemption should not apply to pipe tested beyond 28 days of age, when significant strength gain is no longer expected. Therefore, for pipe tested prior to 28 days of age we propose that if the manufacturer waits a minimum of 24 hours prior to a retest, the requirement to test two pipe for each “failed” pipe would no longer apply.