This is a very interesting paper exposing an anlytical technique for modelling the three-dimensional microstructure of cement paste on a computer screen. One of the major benefits of this technique is that one can see the results of one's calcuations in the real time and can modify the model accordingly. It is hoped that more researchers will use this technique in the future.
As far as I could see, the authors have depended heavily on the observations of Scher and Zallen(1) for the interpretation of the results of their calculations. It has been claimed that a phase, embedded in a matrix, starts to form continuous paths across the marix at a critical fractional volume concentration of 0.16. This critical volume concentration (Vc) has been presented as of "universal" validity without any reference to the size of the individual "particle" of the percolating phase. The authors have used this definition to interpret the results of their calculations and drawn a number of very interesting inferences about the microstructure of cement paste. It will be of interest to see how far this particular definition is valid and how it affects the microstructural inferences drawn by the authors.
- Is V c independent of the "particle" size of the percolating phase? The following examples will indicate that V e may not be independent of the size of the individual "particles" of the percolating phase.