The Cylinder Tests - Reliable in Former or False Prophet?

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Title: The Cylinder Tests - Reliable in Former or False Prophet?

Author(s): James M. Shilstone, Sr

Publication: Concrete International

Volume: 2

Issue: 7

Appears on pages(s): 63-68

Keywords: compacting; compression; compressive strength; concretes; cylinders; density (mass/-volume); ultrasonic tests; vibrators (machinery).

Date: 7/1/1980

Abstract:
The concrete cylinder test is the prime means for assessing concrete strength. Despite years of use, controversy still exists about its accuracy. The paper discusses measured variations within specimens which lead to low results. The problems discussed are: (1) elongated or flat particles becoming vertically oriented in the rodding process resulting in artificial vertical planes of weakness within the cylinders, and (2) compacting of cylinders resulting in nonuniform density. In both cases, the test result is not indicative of the potential strength of the in-place concrete. Tests have indicated results as much as 20 percent below the true strength potential of the concrete. Recommendations are made for the use of vibrators to make cylinders and ultrasound to nondestructively scan a percentage of test cylinders before testing so that results may be properly interpreted.