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Scanning electron microscopy and X-ray imaging techniques have been developed for imaging the complex microstructure of cement-based materials such as cement powder and fly ash. By combining the information available in the backscattered electron and relevant X-ray images, an accurate segmentation of the image into individual cement clinker phases or other components can be accomplished. This paper reviews the image acquisition and processing techniques used in performing this analysis, as well as the statistics that can be used to characterize the final 2-D microstructures, such as area fractions, surface fractions, and two-point correlation functions. In addition, two applications are presented: 1) the imaging of a series of fly ashes from different sources, and 2) the analysis of cement microstructure as a function of grinding fineness. The resultant images provide the quantitative characterization needed for input into three-dimensional computer models of cement hydration and microstructural development.