Cementitious materials are inherently complex from a microstructural viewpoint. The starting cement powder is a multi-size, multi-phase particulate system whose chemical and physical properties control the hydration behavior of the cement paste. While this paper focuses on the microstructure of these materials at the scale of micrometers, it should be noted that such complexity exists at scales ranging from nanometers (the gel structure of the calcium silicate hydrate) to millimeters (the scale of aggregates in the concrete), requiring the application of a multi-scale approach to the microstructural modelling of concrete materials [1].
Scanning electron microscopy is a powerful technique for analyzing cement-based materials [2], and has been applied successfully to cement clinkers [3], cement powders [4,5], and hydrated cement pastes and concretes [6]. The SEM provides high contrast images that can be segmented to identify the component phases comprising the complex cement microstructure. In this paper, the image acquisition and processing techniques used in this process are outlined, spatial statistics that can be used to characterize the 2-D (and 3-D) microstructure are enumerated, and example results for the imaging of both fly ashes and cement powders are presented.