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Bentz et al.  have verified the cement microstructure model by comparing the ITZ microstructures of model and real specimens for systems in which 0, 10, and 20 mass percent of the cement was replaced by silica fume. Specimens consisting of cement paste and coarse aggregate were prepared and phase fraction distributions were measured using scanning elecron microscopy and image analysis. Results are shown in Fig. 8 for the total cement+CSH+silica fume and porosity phase fractions. In Fig. 8, the model results have been scaled along the x-axis so that the average cement particle size, about 40 micrometers, is similar in the two systems. In general, agreement between the two systems is quite good. As seen earlier, silica fume improves the concrete microstructure by decreasing the porosity and increasing the cement+CSH+silica fume phase fraction present in the ITZ as well as in the bulk paste. These phase fractions are nearly homogeneous throughout the 20% silica fume concrete.
Figure 8: Comparison between (a) real (left) and (b) model (right) specimens.