AbstractThe predominant mechanism of transport of chloride ions into concrete is diffusion. The rate of diffusion is largely controlled by the chloride diffusivity or chloride diffusion coefficient of the concrete. The determination of this parameter requires a long test duration and, hence, migration test methods have been developed. The principle of migration tests is to accelerate the transport of chlorides through concrete by the application of an electrical potential difference. However, no migration test has been developed to assess the chloride diffusivity of concrete on site. Therefore, the objective of this research was to develop an in-situ chloride migration test to determine the chloride diffusivity of concrete on site.
To achieve the above objective a portable apparatus was developed that enabled the in-situ migration coefficient of concrete to be determined. The test was standardised and validated by carrying out comparative chloride diffusion tests, using a range of Portland cement concrete mixes. The effectiveness of the new test for on site applications was investigated by carrying out tests on the Dickson Bridge, Montreal.
The in-situ chloride migration test enabled the chloride diffusivity of concrete to be determined in one working day. The in-situ migration coefficient correlated well with the effective and the apparent diffusivity determined from the long-term diffusion tests. The new test was found to be suitable for use on site, where the in- situ migration coefficient correlated well with the chloride content at the level of the reinforcement and the rate of corrosion. These results showed that the new in-situ chloride migration test could accurately determine the chloride diffusivity of concrete.
|Date of Award||Sep 1999|
|Supervisor||P.A.M. Basheer (Supervisor) & D.J. Robinson (Supervisor)|