Statistical Modeling of Pore Structures in Fresh Cement Paste Based on Dispersion Theory of Random Two-Phase Media

Abstract

Pore structures are critical for most properties of cementitious materials. To describe the initial pore structure of fresh cement paste, which is the foundation of the evolution of a pore network induced by hydration of cement particles in hardened concrete, statistical modelling of pore structure is carried out based on a concentric-shell sphere model, by taking cement paste as a random two-phase media. Calculations by the dispersion models agree well with the pore size distributions tested by the low-field H1 nuclear magnetic resonance (NMR) technique. For cement paste that disperses completely with the help of a dispersant, a hard sphere model is practical. However, in most real conditions, an agglomeration of cement particles will occur both before and after mixing with water, which can be characterized by the redistribution of pore size determined by the critical grain size and the hardness parameter in the concentric-shell model, respectively. Calculation results suggest that agglomeration of particles leads to coarser pores. This work will promote the understanding of the formation mechanisms of pore networks and further offers a foundation for modelling the evolution of pore structures in cementitious materials.