- Author
-
Bentz, D. P.
- Title
- Influence of Silica Fume on Diffusivity in Cement-Based Materials. II. Multi-Scale Modeling of Concrete Diffusivity.
- Coporate
- National Institute of Standards and Technology, Gaithersburg, MD
- Journal
-
Cement and Concrete Research,
Vol. 30,
No. 7,
1121-1129,
July 2000
- Distribution
- For more information contact: Website: http://ciks.cbt.nist.gov/bentz/csfdiff2/csfdiff2.html
- Keywords
-
cements
|
concretes
|
diffusion
|
hydration
|
silica fume
- Abstract
- Based on a set of multi-scale computer models, an equation is developed for predicting the chloride ion diffusivity of concrete as a function of water-to-cement (w/c) ratio, silica fume addition, degree of hydration and aggregate volume fraction. Silica fume influences concrete diffusivity in several ways: (1) densifying the microstructure of the interfacial transition zone (ITZ) regions, (2) reducing the overall (bulk and ITZ) capillary porosity for a fixed degree of cement hydration, and (3) producing a pozzolanic C-S-H gel with a relative diffusivity about 25 times less than that of the C-S-H gel produced from conventional cement hydration. According to the equation and in agreement with results from the literature, silica fume is most efficient for reducing diffusivity in lower w/c ratio concretes (w/c < 0.4). In these systems, for moderate additions of silica fume (e.g., 10%), the reduction in concrete diffusivity may be a factor of 15 or more, which may substantially increase the service life of steel-reinforced concrete exposed in a severe corrosion environment.