The particle size distributions (PSDs) for Cements 115 and 116 were measured at the University of Illinois using an x-ray sediograph technique. The result from the test is a curve of cumulative mass fraction smaller than an equivalent spherical diameter. This curve is discretized (binned) into 2 µm increments for use in the three-dimensional cement hydration model. The discretized PSDs determined for Cements 115 and 116 and used in the computer modelling are provided in Table 3. The calculated surface areas along with those measured [5] using the available ASTM techniques [6], are provided in Table 4. While the experimentally measured surfaces areas are seen to be similar although differing between the two techniques, according to the PSD measurement, Cement 116, with an average particle radius of 4.8 µm on a mass basis, is finer than Cement 115, with an average particle radius of 6.1 µm. The surface areas calculated based on the PSDs given in Table 3 are lower than the experimental values due to both the truncation of the PSD (i.e., the elimination of particles smaller than 3 µm ) and the assumption of spherical particle shapes.
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