An Accelerated Method for Measuring the Effective Chloride Diffusion Coefficient of Concrete


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Title: An Accelerated Method for Measuring the Effective Chloride Diffusion Coefficient of Concrete

Author(s): J. G. Cabrera and K. E. Hassan

Publication: Special Publication

Volume: 170


Appears on pages(s): 1551-1576

Keywords: Concretes; diffusion; durability; performance.

Date: 7/1/1997

This paper presents a laboratory accelerated method for measuring the effective chloride diffusion coefficient of concrete using the static diffusion cell technique. The method is based on initially saturating specimens with chlorides before testing them, in order to accelerate the time required to achieve steady state diffusion. The effective diffusion coefficient can be obtained after 7 to 10 weeks. Saturation of specimens was achieved by two procedures. The first one was simple vacuum-saturation, the second method was saturation by the applied voltage technique using 30V or 40V potential difference. The results of these experiments showed that saturating the specimens with chlorides does not affect the diffusion process, as indicated from the chloride concentration profiles across the specimens before and after testing in the diffusion cells. The steady state condition during the diffusion test is only achieved at 10 to 14 days of diffusion time. This is a relatively short time when compared to the time that it takes to obtain results using the conventional method. The total test period was reduced to 7 weeks to obtain the effective diffusion coefficient through relatively thick concrete and mortar specimens (25 mm). Data obtained for a wide range of mortars treated with surface coating compounds and for high performance concrete is compared with values of diffusion coefficients obtained from the unsteady state ponding method. A reasonable statistical conversion equation is proposed in order to compare or convert values of one test to another.