Multi-Scale Microstructural Modeling to Predict Chloride Ion Diffusivity for High Performance Concrete.
Multi-Scale Microstructural Modeling to Predict Chloride
Ion Diffusivity for High Performance Concrete.
Bentz, D. P.; Garboczi, E. J.
Materials Science of Concrete Special Volume: Ion and
Mass Transport in Cement-Based Materials. Proceedings.
American Ceramic Society. October 4-5, 1999, Toronto,
Canada, 253-267 pp, 2001.
chloride ion; diffusivity; concretes; durability;
diffusion; silica fume
As durability issues become increasingly prominent in
concrete design, the need to predict the transport
properties of a given concrete mixture becomes critical.
For many degradation scenarios (corrosion, sulfate
attack, etc.), the diffusion coefficient of the concrete
is a critical parameter that helps determine its service
life. The goal of current research at the National
Institute of Standards and Technology is to develop
predictive equations for the chloride ion diffusivity of
concrete based on mixture proportions and expected
degree of hydration. The basis for these predictions is
a set of multi-scale computer-based microstructural
models for cement-based materials. Modeling at the scale
of micrometers (cement paste) provides the necessary
information on the effects of water-to-cement (w/c)
ratio, silica fume addition, and degree of hydration on
the volume of capillary porosity, and its connectivity.
Modeling at the scale of centimeters (concrete) provides
information on the influence of volume fraction and
gradation of aggregates and interfacial transition zone
(ITZ) microstructure on the effective diffusivity of the
concrete composite. Connecting the models at these two
scales allows for the quantitative estimation of the
chloride ion diffusivity of a specific concrete. Based
on the results of these models, the addition of silica
fume is seen to be a very efficient means for reducing
concrete diffusivity, particularly for low w/c ration