Differential-scheme based dissolution/diffusion model for calcium leaching in cement-based materials accounting for mix design and binder composition

A material model for calcium dissolution/diffusion in cement-based materials is presented, taking the increase of porous space due to calcium leaching into account. The so-called differential-scheme is employed to link the underlying effective diffusive properties to the pore-space volume. The so-obtained material description is used within an analysis scheme based on the finite element method for the simulation of calcium dissolution/diffusion processes at the macroscopic scale. The re-analysis of leaching tests on cement-paste specimens in deionized water and ammonium nitrate solution, respectively, in terms of the rise in calcium concentration in the sample-enclosing aggressive solution, is used for assessment of underlying model assumptions, such as the material function relating calcium concentration bound in solid material skeleton to calcium concentration in the pore fluid. Moreover, the diffusion coefficient of the electrolyte solution in the pore space of cement-based materials, serving as input for determination of the effective diffusion properties, is investigated.