How Soon is Soon Enough?


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Title: How Soon is Soon Enough?

Author(s): Bryant Mather

Publication: Journal Proceedings

Volume: 73

Issue: 3

Appears on pages(s): 147-150

Keywords: age;age-strength relationships; building codes;concrete construction; concretes; fresh concretes; mix pro-portioning;quality control; specifications; tests.

Date: 3/1/1976

The standard 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 extensive debates as to which shape is to be preferred. More recently 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 any concrete 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 such is the case, the grade of concrete will be proper at all ages and testing at any age is merely confirmation.