Chloride diffusion coeficient determination for specifications

The chloride diffusion resistance of reinforced concrete can have a major influence on durability. A move to performance-based specifications is therefore to be encouraged in the case of highway structures, where the client expects a long trouble-free service life. The introduction to practice of service life modelling and performance-based specifications requires a parallel development in user-friendly test methods. This paper reports on experience with three techniques used to determine apparent chloride diffusion coefficients: long-term immersion tests with chloride analysis by Volhard titration, tests of medium duration with chloride analysis by an internal-calibration potentiometric method and short-term Nordtest rapid migration tests. Concrete compositions tested included Portland cement, pfa and ggbs mixes. It was found that medium and long-term tests were consistent, but care is needed with early age tests.