In recent years, a paradigm shift from manual to virtual testing of cement and concrete has nucleated [1]. While perhaps still in its induction stage, numerous examples of the ability of microstructure models to predict a wide variety of the performance properties of cement-based materials have been presented [2-5]. Despite their success in predicting properties, the creditability of these models is still questioned by some. To accelerate their acceptance, a direct comparison of model and real microstructures would be beneficial.
While comparisons between two-dimensional images of real and model microstructures were presented in one of the first two papers [6] describing the CEMHYD3D microstructure model, a direct three-dimensional comparison was not possible at that time. However, with the development of the Visible Cement Data Set [7] (currently available at http://visiblecement.nist.gov), a direct comparison between real and computer model three-dimensional microstructures is now possible. The Visible Cement Data Set consists of a series of x-ray computed microtomographic 3-D images of unhydrated and hydrated cement pastes (along with a few images of hydrating calcium sulfate hemihydrate) obtained with a voxel dimension of 0.95 µm at the European Synchrotron Radiation Facility (ESRF) in 20000. The data were acquired for Cement and Concrete Reference Laboratory (CCRL) proficiency cement sample 133 [8], which has been used extensively in the development and refinement of the CEMHYD3D microstructure model [9]. In this paper, a direct comparison between the x-ray microtomography images and images generated by the CEMHYD3D microstructure model is presented.