Feasibility Study of the Development of an In Situ Chloride Migration Test
P. A. Muhammed Basheer, Peter R. V. Gilleece,
Robin Andrews, and Adrian E. Long
Appears on pages(s):
chlorides; diffusion; electrical resistance; nondestructive tests
The resistance of concretes to the transport of chloride ions is defined generally by the coefficient of diffusion. This, combined with a knowledge of the exposure of concrete to chlorides, can be used to estimate the depth of penetration of chlorides over a period of time. Therefore, an indication as to the likelihood of chlorides reaching reinforcement can be determined, and, if there is a risk of corrosion, preventive measures can be taken. The procedure to find the coefficient of diffusion from a standard diffusion test is well established. However, such a test may need several months to finish, depending on the quality of the concrete and the thickness of sample tested. As a consequence this is not a practicalmethod, and different organisations have conducted research to determine the coefficient of diffusion (D) more rapidly. The approach adopted has been to force chlorides through the test sample by applying a voltage, and such tests are known as accelerated chloride migration tests. By using this principle, and following from early studies by Whiting, a new test method for determining the chloride migration coefficient of the near surface concrete in-situ is being developed at Queen’s. This test makes use of a set up similar to the well established Autoclam permeability system. The results of an investigation carried out with this new apparatus is presented in this paper along with a description of the new test method. Early results indicated that this new test method could form the basis to determine the chloride diffusivity of the near surface concrete on site.