ASS’J!RACT : Characterization of cement particles is complicated due to their wide eize range, G.omplexshapes, and multi-phase nature. Accurate characterization should allow for better prediction of cement performance and more realistic modelling of cement microstructural development. This paper presents a’technique, based on scanning electron microscopy and digital image proceeding, for obtaining twodimensional digital images of actual portland cement particles in which all major phaaes are identified. By combining backscattered ~lectron and X-ray images, an image segmented into the major cement phases may be created. These images can be analyzed to determine any number of quantitative meaeures euch as phase fractions orphaae perimeters. The technique has aleo been successfully utilized in obtaining realistic etarting images for input into a two-dimensional cement microstructure model which sfmulatee the hydration process.