ISSN: 0149-6123
Page Count: 4

A Comparison of Two Methods for Measuring the Chloride Ion Permeability of Concrete
Detwiler, RJ
Assistant professor and graduate student, University of Toronto, Ontario

Fapohunda, CA
Assistant professor and graduate student, University of Toronto, Ontario

Abstract

The AASHTO T 277 test (recently adopted as ASTM C 1202) for chloride permeability is widely used. However, a number of researchers have criticized it for various reasons: (1) it is sensitive to differences in pore solution chemistry and therefore exaggerates the effectiveness of supplementary cementing materials in reducing permeability; (2) the relation between electrical conductivity and ion diffusion varies with the type of diffusion, making the test sensitive to small defects in the concrete; and (3) the measurement is taken before steady-state flow is achieved. This paper reports the results of parallel tests on 18 different concretes using both AASHTO T 277 and a modified version called the Norwegian test. The latter test provides a direct measure of the migration of chloride ions over time. The results show that although both tests lead to the same broad conclusions, they do not rank a series of concretes in the same order. The differences can be attributed largely to differences in pore solution chemistry. However, the AASHTO T 277 test has several advantages over the Norwegian test. Provided the results are interpreted correctly, it could be the more appropriate method in many cases.

Keywords:
AASHTO T 277, chloride, concrete corrosion, permeability, test methods

Paper ID: CCA10589J
DOI: 10.1520/CCA10589J
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