Interpreting the Pore Structure of Hydrating Cement Phases Through a Synergistic Use of the Powers-Brownyard Model, Hydration Kinetics, and Thermodynamic Calculations

Abstract

Abstract The Powers-Brownyard model is an analytical tool that is widely used to quantify the volume of gel solids, gel pores, capillary water, and unhydrated cement during the hydration process. These parameters, specifically the capillary and gel pore volumes, are related to important hardened concrete properties, such as shrinkage, freeze-thaw, transport, and strength. While the Powers-Brownyard model has many applications, it does not provide detailed solid phase assemblage information, and it can only be used for ordinary portland cement. In contrast, thermodynamic modeling can predict solid phase assemblage for a wide range of cementitious binders, but does not provide information on the resulting pore structure. This work combined the Powers-Brownyard model, hydration kinetics, and thermodynamic calculations to predict capillary and gel porosity, chemical shrinkage, and volumes of all hydrated and unhydrated phases for plain cement pastes without the need for additional information such as pore size distributions. This new model has the advantages of both the Powers-Brownyard model and thermodynamic modeling, and is a powerful tool, which the authors envision to be used to further advance the understanding of durability of cementitious materials.