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Multiscale Analytical/Numerical Theory of the Diffusivity of Concrete.

Multiscale Analytical/Numerical Theory of the
Diffusivity of Concrete.
(1402 K)

Garboczi, E. J.; Bentz, D. P.

Advanced Cement Based Materials, Vol. 8, 77-88, 1998.

### Keywords:

concretes; concrete diffusivity; durability; interfacial
transition zone; microstructure; modeling; performance
prediction; statistical geometry

### Abstract:

*
The ionic diffusivity of a concrete is a function of its
microstructure at many length scales, ranging from
nanometers to millimeters. The microstructure is
largely controlled by the initial concrete mixture
proportions and ultimate curing conditions. Linking a
property like ionic diffusivity to the microstructure
then requires a multiscale approach. A multiscale
microstructural computer model for ionic diffusivity has
been previously developed. This model has been developed
specifically to compute the chloride diffusivity of
concrete with various mixture proportions and projected
degrees of hydration. The three key parts of this model
were dependent on large-scale supercomputer-magnitude
simulations to: (1) determine the total volume of
interfacial zones for a given aggregate distribution,
(2) simulate the hydrated cement paste microstructure
around a typical aggregate, and (3) compute the effect
of the aggregates and interfacial zones on the overall
diffusivity of the concrete. The key feature of this
model is that one can approximately take into account
the redistribution of cement paste between interfacial
transition zone regions and bulk paste regions, and its
important effect on overall concrete diffusivity. In
the present article, we review the previously developed
model and show how analytical equations can accurately
replace the large scale computer simulations of parts
(1) and (3). This accomplishment will make the model
more usable by those who do not have access to
supercomputer computing power.
*