Figures 13 and 14 show the results of applying the CA hydration algorithm to the original microstructure of Figure 9 (W/C = 0.672) to achieve degrees of hydration of 30% and 76%. From these figures, the capability of the CA code to generate complex microstructures based on the iterative application of relatively simple rules should be manifest.
In these figures, a yellow layer of C-S-H gel can be seen forming around each of the cement particles (particularly the silicate regions of these particles). We believe that it is the formation and interlinking of these growing layers which leads to the setting of the cement pastes; this is supported by recently published experimental evidence (Chen and Odler 1992) as well as our ongoing work using ATR/FTIR spectroscopy. The randomly-formed pore products would require a much larger volume of product to percolate as they do not attach specifically to the existing framework of cement particles. Thus, their contribution to the onset of solids percolation should only be significant in cements containing large quantities (more than 20%) of tricalcium aluminate which hydrates rapidly. For most conventional cements, then, set will ultimately be controlled by the production of the C-S-H gel.
