All simulations were conducted using a modified set of the CEMHYD3D V2.0 computer programs [18]. Starting microstructures that matched the w/c, particle size distribution, phase composition, and phase distribution of cement 152 were created. Because no water-reducing agents were used in the experiment, the cement particles were flocculated prior to hydration [5]. Hydration simulations were conducted under sealed conditions and the percolation of the solids was monitored to compare to the physical measurements of setting [19]. During the percolation evaluation, two touching (flocculated) particles are not considered to be connected unless they are bridged by some volume of hydration products, specifically the C-S-H or one of the aluminate hydration products [2, 5, 19]. The volume fraction of the connected solids, bridging from one side of the microstructure to the opposite one, averaged over the three principal directions, was recorded as a function of hydration cycles. For hydration at 25 ºC, a conversion factor of 0.00035 h/cycle2 was used to convert between hydration cycles (squared) and real time [12].