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Set Point- Percolation of Solids

In the first application, the datafile for which is provided in Appendix D.2, we will examine the percolation of total solids, related to setting behavior, of a cement paste with a w/c ratio of 0.4, for a system in which all of the cement particles have been flocculated into a single floc structure. For this application, the hydration will be executed under isothermal and saturated conditions. In addition, the dissolution bias parameter in the program disreal3d.c, DISBIAS, has been increased from 20.0 to 100.0, to reduce the dissolution rate and increase our resolution in observing the percolation behavior. Twenty cycles of the hydration are executed, with the solids percolation being determined after each cycle. In the model, total solids percolation is defined as the fraction of cement particle and hydration product (specifically C-S-H and ettringite) pixels for which the cement particles are connected together by either ettringite or C-S-H gel. Thus, two touching cement particles do not comprise a connected pathway unless they are also bridged by either a layer of C-S-H or ettringite.

Figure 5 provides a plot of the connected fraction of total solids vs. the achieved degree of hydration for this system. In this case, set occurs in the range of hydration of 2.5 to 3%, consistent with previous computer modelling results [16] using a model based solely on C₃S hydration [17] and experimental results based on measuring a shear resistance of 0.08 MPa for the cement paste [9].