- Author
- Clifton, J. R. | Knab, L. I. | Garboczi, E. J. | Xiong, L. X.
- Title
- Chloride Ion Diffusion in Low Water-To-Solid Cement Pastes.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Sponsor
- Nuclear Regulatory Commission, Washington, DC
- Report
- NISTIR 4549, April 1991, 30 p.
- Distribution
- Available from National Technical Information Service
- Keywords
- cements | chloride ion | concretes | corrosion | diffusion coefficient | fly ash | service life
- Abstract
- Diffusion coefficients of 0.3 water to solids ratio (w/s) hydrated portland cement paste specimens were measured using a conventional diffusion cell. Specimens were made from both ASTM Type I and Type II portland cements and blends containing mineral admixtures (fly ash, granulated blast furnace slag, or silica fume). The average diffusion coefficient for the portland cement paste specimens was 14x10(-13) m(2)/s. The diffusion coefficients for the specimens containing mineral admixtures were much more variable than those for the portland cement paste specimens. A probable cause of the variability in the test results was the presence of cracks observed in the test specimens. The effects of the depth of concrete cover over reinforcing steel and of the chloride ion diffusion coefficient on the service life of reinforced concrete exposed to chloride ions were predicted based on a diffusion model. Based on the model, the effect of the cover was shown to be proportional to the square of the cover depth. A 10-fold decrease in the diffusion coefficient of concrete was predicted to result in a 10-fold increase in the predicted service life. Based on the results of the present study, it is recommended that a new chloride diffusivity test should be developed which is applicable to concrete. A candidate test method is proposed.