How Soon is Soon Enough? Revisited


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Title: How Soon is Soon Enough? Revisited

Author(s): Bryant Mather

Publication: Special Publication

Volume: 141


Appears on pages(s): 1-10

Keywords: age-strength relation; building codes; concrete construction; concretes; fresh concretes; mix proportioning; quality control; specifications; tests; General

Date: 12/1/1993

The customary criterion for establishing grades of structural concrete is the crushing strength measured in an arbitrary manner on a standardized specimen stored in a stipulated fashion for approximately a month after making. In some parts of the world, the specimen is a cube, and in other parts of the world, the specimen is a cylinder. There have been debates as to how the strength at 28 days can be predicted from procedures performed at early ages, especially 24 hr, on the grounds that a month is not soon enough. The intent of this paper is to suggest that the only time that really is "soon enough" to know that the grade of the concrete in any batch is correct is before the concrete is discharged from the concrete mixer into the forms. It is suggested, therefore, that effort would preferably be expended upon insuring that the materials used are those intended and the proportions in which they are used are those that were intended. If this is the case, the grade of concrete will be proper at all ages, and testing at any age is merely confirmation.