Conclusions

The knowledge of a bulk and surface phase composition of hydraulic cement should provide new insights into early-age hydration characteristics, cement-chemical admixture interactions, and aid in developing new hydraulic cements. These measurements are made possible through the imaging capabilities of the scanning electron microscope with imaging and X-ray microanalysis by:

1. backscattered electron SEM, combined with X-ray imaging provides the basis for a quantitative assessment of the phases in portland cement,
2. segmentation into the individual phases is achieved by a combination of imaging 'rules' and individual constituents may be highlighted using false color,
3. the resulting composite image can be analyzed to calculate volume percent, mass percent, and percentages based upon surface area measurements of the individual phases,
4. mass percentages obtained by this procedure are in good agreement with percentages based upon QXRD and may differ significantly from those estimated by the Bogue calculations, and
5. phase fractions by surface area show considerable difference from those expressed as bulk mass fractions. The finer-grained phases (gypsum, tricalcium aluminate, and ferrite) show much higher surface areas per unit mass than the coarser-grained phases such as alite and belite.