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Title: Investigation of Compressive Strength of Molded Cylinders and Drilled Cores of Concrete

Author(s): Bryant Mather and William O. Tynes

Publication: Journal Proceedings

Volume: 57

Issue: 1

Appears on pages(s): 767-778

Keywords: none

Date: 1/1/1961

Abstract:
This work was done to obtain information on methods being used to estimate the 28-day compressive strength of concrete. Its primary purpose was to determine the rela- tion between the 28-day compressive strength of 6 x 12-in cylinders molded from samples of concrete mixtures from which aggregate larger than 1 1/2 in. had been removed, and that of 6-. 8-. and 10-in. diameter cores drilled from test structures and containing aggregate graded to 3-in. or 6-in. size. A secondar purpose of the study was to determine the strength re ations of 6 x 12-in. concrete l cylinders cured in the field and comparable cylinders cured in the laboratory under standard conditions. The results suggest that estimates of the 28-day compressive strength of concrete containing 3- or 6-in. aggre- gate will not be significantly different whether based on results of compressive strength tests of similarly cured 6 x 12-in. cylinders of the same concrete wet-screened over a 1 X-in. sieve, or on results of tests of 6-, 8-, or IO- in. diameter cores drilled from the structure and having a height equal to twice the diameter. The results suggest, however, that the smaller the core diameter, the larger the number of test cores should be to yield results of a given precision. It is indicated that cores should be more than 11 in. in diameter to give as precise an estimate of strength as that given by an equal number of 6 x 12-in. cylinders. As has been indicated by many previous studies, compari- son of the Field-cured and standard-cured cylinders showed that concrete cured at lower temperatures has a lower compressive strength than concrete cured under standard conditions.