Influence of Core Dimensions on Mean Compressive Strength Results and Their Dispersion

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Title: Influence of Core Dimensions on Mean Compressive Strength Results and Their Dispersion

Author(s): Arlindo Goncalves

Publication: Special Publication

Volume: 128

Issue:

Appears on pages(s): 529-542

Keywords: compressive strength; concretes; cores; curing; dispersions; standard deviation; Materials Research

Date: 11/1/1991

Abstract:
During a comprehensive research program on in situ determination of concrete strength, the influence of core dimensions on mean compressive strength results and their dispersion was studied. Tests were conducted on 14, 11, 9, and 5 cm diameter cores, usually with a length/diameter ratio l/d = 1; cores with l/d less than 1 were also tested. Cores were drilled from 20 cm cast concrete cubes, stored in a moist room. When using 5 cm diameter cores, the curing conditions of the cubes were varied. The 28-day strength results showed that dispersion increases with increases in concrete strength, maximum aggregate size, and reduction of core diameter. A good correlation was found between the mean compressive strengths of cubes and cores, both for the results of cores with l/d = 1 and l/d = 0.6. The mean compressive strengths of cores were the same as those for cubes and were not influenced by the core diameter. Thus, the use of small diameter cores may be possible. In this case, however, the concrete from the surface must be removed when preparing the cores, if the concrete was not moist-cured.