Influence of Silica Fume on Diffusivity in Cement-Based Materials. II. Multi-Scale Modeling of Concrete Diffusivity.
Influence of Silica Fume on Diffusivity in Cement-Based
Materials. II. Multi-Scale Modeling of Concrete
Diffusivity.
(924 K)
Bentz, D. P.
Cement and Concrete Research, Vol. 30, No. 7,
1121-1129, July 2000.
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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.
