STUDY OF UNIFORMITY OF CONCRETE FLEXURAL STRENGTH TEST RESULTS.

The following tentative conclusions are based on the tests conducted, which were comparatively limited in scope Considerable variation in flexural strength test results may be expected for specimens taken from the same concrete mix, even under the best controlled conditions of preparing, curing and testing of the specimens. A variation in flexural strength of 10 percent from the average value is not considered to be a satisfactory criterion for rejection of individual test results. A variation in flexural strength of 15 percent from the average value may be considered significant when the difference cannot be attributed to variations in the concrete mix. The rejection of individual values under any of the criteria considered has only a minor effect on the average strength of a group of specimens, and the effect becomes less as the number of specimens in the group increases. Author