Model for the Developing Microstructure in Portland Cement Pastes

A method is proposed for quantitatively predicting the volume of the major phases in hydrated cement pastes as a function of (1) the composition of the cement, (2) the degree of reaction, and (3) the initial water:cement ratio. This procedure is then used to develop a quantitative model for the surface area and volume of porosity that is accessible to nitrogen in C-S-H. Published values for surface areas and volume of pores are compared with the predictions made by the model. An implication of the model is that there are two types of C-S-H, or perhaps regions within the C-S-H: one that nitrogen can penetrate and one that it cannot.