Time dependent chloride diffusion coefficient - field studies of concrete exposed to marine environment in Norway
Chloride ingress in concrete results in a chloride profile illustrating the time and depth dependent distribution chloride content within the concrete. The apperent chloride diffusion coefficient calculated from the chloride profile is time dependent and reduces over time due to increased concrete maturity and tightening of the exposed concrete surface layer. In service life calculations this time dependency of the diffusion coefficient is taken into account byn an ageing factor. From earlier tests this age effect was found to obey a straight line in a double logarithmic coordination system. However, the data for this ageing exponent are scare. moreover, the achieved service life is very sensitive to the chloice of this value. The present paper deals with a survey of available Norwegian test data on concrete exposed to maine environment. the most reliable data in this survey show significant difference between concrete with CEM I binder anc concrete with silica fume and/ or CEM II binders, as the ageing factor is much larger for the latter concrete types. Most of the data only represents the development over a few years after exposure, and the amount of reliable data and long term exposure (> 10 years) is limited. The investigations does, however, also include reliable data for concrete exposed for 10 years, and these data indicate that the chloride diffusion coefficient reduction declines after approximately 5-10 years.
- Gro Markeset
- Ola Skjølsvold
- SINTEF Community / Architecture, Materials and Structures
2nd International Symposium on Service Life Design for Infrastructure
04.10.2010 - 06.10.2010