The hydration behavior of portland cement phases continues to be debated with new insights fueling the controversy. What causes the induction period? What initiates acceleration? What causes the onset and rapid decrease in reaction rate post peak? Does diffusion play a role and what causes low, but sustained reaction rates for long periods of time? Recent modeling efforts suggest that boundary nucleation and growth can explain at least some of the observations and that such occurs in a "limited reaction volume'' accounting for about 30% of the initial cement mass. Yet, other efforts offer an alternative theory that would suggest that densification occurs in two steps. In an effort to resolve these and other questions, a single particle model for alite/Ca3SiO5 hydration has been developed using a mass continuity-based continuum approach as an alternative to the Avramian basis used in most recent studies. Such single particle models are relevant starting points for fast model-based experimentation, more elaborate single particle models, and simulation platforms that act on ensembles of particles. The present model includes transport effects, solution phase chemistry, and incorporates intraparticle nucleation.