Modeling electrolyte diffusion in cracked cementitious materials using cascade continuum micromechanics and phase-field models

Electrolyte transport in fracturing porous materials such as concrete is strongly influenced by the complex and random topological structure of the pore space, the state of distributed microcracks inevitably caused by autogenous and drying shrinkage of concrete and finally by propagating cracks caused by various loading conditions. Information on macroscopic diffusion properties of the intact concrete requires up-scaling of transport processes within nano- and micro-pores over several spatial scales. The macroscopic transport coefficients are computed using a cascade continuum micromechanics model. The cascade continuum micromechanics model recursively embeds shape information in the form of the ESHELBY matrix-inclusion problem to obtain the homogenized effective diffusivity as a function of a perturbation index and the porosity. The effects of the microstructure on the transport properties are characterized by porosity dependent short range and long range inter-phase interactions. To take into consideration the effects of oriented, diffusely distributed micro-cracks on electrolyte diffusion properties, the homogenization scheme for electrolyte diffusion in intact concrete is enhanced by representing micro-cracks as additional ellipsoidal inclusions within the aforementioned homogenized porous matrix. Finally, the effect of propagating macro-cracks on the diffusion process is taken into consideration by weakly coupling the diffusion model and a fracture energy based staggered phase-field model to simulate brittle fracture.