Random field finite element models with cohesive-frictional interactions of a hardened cement paste microstructure

Cement paste is a disordered material whose properties and structure differ spatially and cannot be precisely predicted. We propose a new approach for developing finite element models of a hardened microstructure that accounts for the stochastic nature of cement paste. The initial model configuration is a random field that is generated according to probability density functions measured through nanoindentation experiments on samples composed of Portland cement and a volcanic ash additive. We study the influence of cohesive-frictional interactions through a Mohr-Coulomb yield criterion applied to the finite element constitutive relations. An ensemble of microstructures are simulated to assess the influence of spatial fluctuations and plasticity on the mechanical response to compressive loading. Our results indicate that the micron-scale morphology has a limited influence on the macroscopic strength behavior. These findings suggest that the shear strength scaling and dilatant behavior of cement paste originates within nanometer-scale features of the composite.