2011 Volume 65 Issue 1 Pages 360-367
The purpose of this study is to improve the concrete durability by using silica fume. The apparent diffusion coefficients of chloride ion of silica fume concrete were measured. Silica fume was effective in reduction of apparent diffusion coefficients of chloride ion. The replacement ratio of silica fume 8％ was more effective in reduction of apparent diffusion coefficients of chloride ion than 4％. In order to clarify this mechanism, the diffusion coefficients of oxygen and pore size distribution were measured. There is a good correlation between apparent diffusion coefficients of chloride ion and diffusion coefficients of oxygen. From this result, it was confirmed that the reduction of apparent diffusion coefficients of chloride ion was brought about by microstructural change by using silica fume. Silica fume was effective in reduction of pore volume which had more than 10nm in diameter. The reduction of apparent diffusion coefficients of chloride ion was caused by reduction of the pore volume. In addition, the time to steel corrosion initiation in silica fume concrete was estimated by using apparent diffusion coefficients of chloride ion which was measured in this study. In this estimation, the critical total chloride concentration was calculated using Cl－/OH－ ratio, OH－ ion concentration in pore solution and chloride binding capacity. As a result, the time to steel corrosion initiation in silica fume concrete was longer than the time in OPC concrete.
