Microstructure-based modeling of the diffusivity of cement paste with micro-cracks

Abstract

The diffusivity of cement-based materials can be significantly increased because of the presence of defects, and in consequence, the service life of concrete structures is reduced. Numerical simulations present an alternative approach to track the property changes of cement-based materials during a specific degradation process on the basis of microstructure evolution. This paper illustrates numerical simulations of the diffusivities of cement pastes with micro-cracks caused by tensile loading and frost action, respectively. Based on a numerical model HYMOSTRUC3D, an original microstructure of cement paste is first generated. Then, the creation of micro-cracks in the microstructure of cement paste where uni-axial tensile load or frost action is applied is simulated by a 3D lattice fracturing model. The diffusivity changes of cement pastes are predicted from a series of 3D diffusive lattice networks which are converted from the microstructures of cement pastes with micro-cracks. Simulations illustrate that the diffusivity of cement paste attributed to tensile loading increases with the increasing tensile strain and the diffusivity increase perpendicular to loading direction is higher than that in the loading direction because of the orientation of micro-cracks. For cement paste subjected to frost action, the diffusivity increases with the decreasing temperature and no direction dependence is found.