Prediction is based on a one-dimensional finite difference solution
of Fick's second law of diffusion, with a variable external chloride
concentration and a two-layer representation of the concrete.
External chloride concentration 1 moles/liter assumed constant for duration 1
Duration 1 days
External chloride concentration 2 moles/liter assumed constant for duration 2
Duration 2 days
Total duration of exposure days
Unexposed boundary condition is
Constant at zero
Reflecting boundary (no chloride escape)
Member thickness m
Depth of Reinforcement mm
Degree of hydration
Volume fraction of aggregate %
Air content %
Initial chloride concentration of concrete g chloride/g cement Guidance
Click here to view database of
concrete diffusivities from literature.
Note that all diffusivities should be apparent diffusivities as we are
modelling transport in the pore space of the concrete using Fick's second
D (bulk concrete) m*m/s
The surface layer of the concrete may have a different (lower or higher) D
value than the bulk concrete due to carbonation or poor curing practices.
Input the surface layer D value and the thickness of this layer. To bypass
this feature, set the skin layer thickness to 0.0 or use D(surface concrete)=
D (surface concrete) m*m/s
Thickness of surface layer mm
Based on a Langmuir isotherm of the form:
where C(bound) is in (mole Cl-)/kg cement and
C(free) is in (mole Cl-)/L
Rate constant for binding s-1
Assuming the formation of Freidel's salt from all of the
C3A and C4AF initially available in the cement powder.
C4AF content of cement % on a mass basis
Rate constant for aluminate reactions with chloride s-1
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