Obtaining More From the Electrical Chloride Test

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Title: Obtaining More From the Electrical Chloride Test

Author(s): P. A. Claisse and T. W. Beresford

Publication: Special Publication

Volume: 170

Issue:

Appears on pages(s): 1119-1132

Keywords: Chlorides; concretes; diffusion; electrical properties; pozzolans.

Date: 7/1/1997

Abstract:
The electrical chloride test was developed some years ago and is carried out by driving chlorides through concrete samples using electric fields with high voltages up to 60 V. In the test, the total current passing through the sample in a few hours is used as an estimate of the transport properties of the chlorides in the concrete. This test has major advantages that it is rapid, and can be used insitu; and, it has been accepted by the ASTM. It has been criticised in the literature and has, for example, been found to give misleading results when pozzolanic materials are present. It has been pointed out by the author that if silica fume is added to the concrete, the current falls during the test. However, in plain concretes it normally rises. This paper is based on the premise that the current test procedure only makes use of part of the available data . Therefore, it provides only part of the possible results for evaluation and analysis. By analys in the shape of the current-time curve, mu’c h more information about the constituents and properties of the concrete may be obtained. For the data presented in this paper, a large number of samples were tested and computer analysis of the shape of the current-time transients was used to identify the causes of the different attributes of the current-time transients. This analysis is of particular importance in Europe where new Eurocodes for cement permit addition of pozzolanic materials to almost all cements.